Add an experimental basic_static_cstring template in example/

This introduces an alternative to basic_static_string designed for use in POD types: Trivially copyable, having a sizeof == N + 1, with no embedded NULs. Placed in example/ to gather user feedback before committing to a public API. See issue #23.
Fix our deduction guide
2026-01-21 17:32:16 +00:00 · 2025-12-19 19:32:30 +01:00 · 2025-12-19 18:26:40 +01:00 · 2025-12-19 18:23:33 +01:00 · 2025-12-19 18:23:33 +01:00 · 2025-12-19 18:23:33 +01:00
24 changed files with 1955 additions and 590 deletions
--- a/.drone.star
+++ b/.drone.star
@@ -2,116 +2,116 @@
 # subject to the Boost Software License, Version 1.0. (See accompanying
 # file LICENSE.txt)
 #
-# Copyright Rene Rivera 2020.
-# Copyright Alan de Freitas 2022.
-
+# Copyright (c) 2020 Rene Rivera
+# Copyright (c) 2022 Alan de Freitas
+# Copyright (c) 2022-2025 Alexander Grund

 # For Drone CI we use the Starlark scripting language to reduce duplication.
 # As the yaml syntax for Drone CI is rather limited.
-#
-#
-globalenv={'B2_CI_VERSION': '1', 'B2_VARIANT': 'release'}
-linuxglobalimage="cppalliance/droneubuntu1804:1"
-windowsglobalimage="cppalliance/dronevs2019"
+
+# Base environment for all jobs
+globalenv={'B2_VARIANT': 'release'}
+
+# Wrapper function to apply the globalenv to all jobs
+def job(
+        # job specific environment options
+        env={},
+        **kwargs):
+  real_env = dict(globalenv)
+  real_env.update(env)
+  return job_impl(env=real_env, **kwargs)

 def main(ctx):
  return [
-  # Priorities: (no 2a, no betas)
-  #
-  # coverage
-  # latest gcc: 17,20
-  # latest clang: 17,20
-  # oldest gcc: 11
-  # oldest clang: 11
-  # asan
-  # tsan
-  # ubsan
-  # valgrind
-  # arm64
-  # s390x
-  # docs
-  # cmake superproject
-  # cmake install
-  # (...the rest)
+    job(compiler='clang-3.8', cxxstd='11,14',          os='ubuntu-16.04'),
+    job(compiler='clang-3.9', cxxstd='11,14',          os='ubuntu-18.04'),
+    job(compiler='clang-4.0', cxxstd='11,14',          os='ubuntu-18.04'),
+    job(compiler='clang-5.0', cxxstd='11,14,1z',       os='ubuntu-18.04'),
+    job(compiler='clang-6.0', cxxstd='11,14,17',       os='ubuntu-18.04'),
+    job(compiler='clang-7',   cxxstd='11,14,17',       os='ubuntu-18.04'),
+    job(compiler='clang-8',   cxxstd='11,14,17,2a',    os='ubuntu-18.04'),
+    job(compiler='clang-9',   cxxstd='11,14,17,2a',    os='ubuntu-18.04'),
+    job(compiler='clang-10',  cxxstd='11,14,17,2a',    os='ubuntu-18.04'),
+    job(compiler='clang-11',  cxxstd='11,14,17,2a',    os='ubuntu-22.04'),
+    job(compiler='clang-12',  cxxstd='11,14,17,20',    os='ubuntu-22.04'),
+    job(compiler='clang-13',  cxxstd='11,14,17,20,2b', os='ubuntu-22.04'),
+    job(compiler='clang-14',  cxxstd='11,14,17,20,2b', os='ubuntu-22.04'),
+    job(compiler='clang-15',  cxxstd='11,14,17,20,2b', os='ubuntu-22.04', add_llvm=True,
+        env={'B2_CXXFLAGS': '-Werror'}),
+    job(name='Clang 15 standalone', compiler='clang-15',  cxxstd='17,20,2b', os='ubuntu-22.04', add_llvm=True,
+        env={'B2_CXXFLAGS': '-Werror', 'B2_DEFINES': 'BOOST_STATIC_STRING_STANDALONE'}),

-  # Coverage
-  linux_cxx("Coverage", "g++-8", packages="g++-8", buildscript="drone", buildtype="codecov", image=linuxglobalimage, environment={'COMMENT': 'codecov.io', 'LCOV_BRANCH_COVERAGE': '0', 'B2_CXXSTD': '11', 'B2_TOOLSET': 'gcc-8', 'B2_DEFINES': 'BOOST_NO_STRESS_TEST=1', "CODECOV_TOKEN": {"from_secret": "codecov_token"}, "COVERALLS_REPO_TOKEN": {"from_secret": "coveralls_repo_token"}}, globalenv=globalenv),
+    job(compiler='gcc-4.8',   cxxstd='11',             os='ubuntu-16.04'),
+    job(compiler='gcc-4.9',   cxxstd='11',             os='ubuntu-16.04'),
+    job(compiler='gcc-5',     cxxstd='11,14,1z',       os='ubuntu-18.04'),
+    job(compiler='gcc-6',     cxxstd='11,14,1z',       os='ubuntu-18.04'),
+    job(compiler='gcc-7',     cxxstd='11,14,1z',       os='ubuntu-18.04'),
+    job(compiler='gcc-8',     cxxstd='11,14,17,2a',    os='ubuntu-18.04'),
+    job(compiler='gcc-9',     cxxstd='11,14,17,2a',    os='ubuntu-18.04'),
+    job(compiler='gcc-10',    cxxstd='11,14,17,20',    os='ubuntu-22.04'),
+    job(compiler='gcc-11',    cxxstd='11,14,17,20,2b', os='ubuntu-22.04'),
+    job(compiler='gcc-12',    cxxstd='11,14,17,20,2b', os='ubuntu-22.04'),

-  # Latest gcc
-  linux_cxx("GCC 12: C++17,20", "g++-12", packages="g++-12", buildscript="drone", buildtype="boost", image="cppalliance/droneubuntu2204:1", environment={'B2_TOOLSET': 'gcc-12', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '17,20'}, globalenv=globalenv),
-  linux_cxx("GCC 12: C++17,20 Standalone", "g++-12", packages="g++-12", buildscript="drone", buildtype="boost", image="cppalliance/droneubuntu2204:1", environment={'B2_TOOLSET': 'gcc-12', 'B2_CXXFLAGS': '-Werror', 'B2_DEFINES': 'define=BOOST_STATIC_STRING_STANDALONE', 'B2_CXXSTD': '17,20'}, globalenv=globalenv),
+    job(name='Coverage', buildtype='codecov', buildscript='codecov_coveralls', env={'LCOV_BRANCH_COVERAGE': 1, "COVERALLS_REPO_TOKEN": {"from_secret": "coveralls_repo_token"}},
+        compiler='gcc-8',     cxxstd='11,14,17,2a',    os='ubuntu-18.04'),
+    # Sanitizers
+    job(name='ASAN',  asan=True,
+        compiler='gcc-12',    cxxstd='11,14,17,20',    os='ubuntu-22.04'),
+    job(name='UBSAN', ubsan=True,
+        compiler='gcc-12',    cxxstd='11,14,17,20',    os='ubuntu-22.04'),
+    job(name='TSAN',  tsan=True,
+        compiler='gcc-12',    cxxstd='11,14,17,20',    os='ubuntu-22.04'),
+    job(name='Clang 14 w/ sanitizers', asan=True, ubsan=True,
+        compiler='clang-14',  cxxstd='11,14,17,20',    os='ubuntu-22.04'),
+    job(name='Clang 11 libc++ w/ sanitizers', asan=True, ubsan=True, # libc++-11 is the latest working with ASAN: https://github.com/llvm/llvm-project/issues/59432
+        compiler='clang-11',  cxxstd='11,14,17,20',    os='ubuntu-20.04', stdlib='libc++', install='libc++-11-dev libc++abi-11-dev'),
+    job(name='Valgrind', valgrind=True,
+        compiler='clang-6.0', cxxstd='11,14,1z',       os='ubuntu-18.04', install='libc6-dbg libc++-dev libstdc++-8-dev'),

-  # Latest clang
-  linux_cxx("Clang 15: C++17,20", "clang++-15", packages="clang-15 libstdc++-10-dev", llvm_os="jammy", llvm_ver="15", buildscript="drone", buildtype="boost", image="cppalliance/droneubuntu2204:1", environment={'B2_TOOLSET': 'clang-15', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '17,20'}, globalenv=globalenv),
-  linux_cxx("Clang 15: C++17,20 Standalone", "clang++-15", packages="clang-15 libstdc++-10-dev", llvm_os="jammy", llvm_ver="15", buildscript="drone", buildtype="boost", image="cppalliance/droneubuntu2204:1", environment={'B2_TOOLSET': 'clang-15', 'B2_CXXFLAGS': '-Werror', 'B2_DEFINES': 'define=BOOST_STATIC_STRING_STANDALONE', 'B2_CXXSTD': '17,20'}, globalenv=globalenv),
+    # libc++
+    job(compiler='clang-6.0', cxxstd='11,14,17,2a',    os='ubuntu-18.04', stdlib='libc++', install='libc++-dev libc++abi-dev'),
+    job(compiler='clang-7',   cxxstd='11,14,17,2a',    os='ubuntu-20.04', stdlib='libc++', install='libc++-7-dev libc++abi-7-dev'),
+    job(compiler='clang-8',   cxxstd='11,14,17,2a',    os='ubuntu-20.04', stdlib='libc++', install='libc++-8-dev libc++abi-8-dev'),
+    job(compiler='clang-9',   cxxstd='11,14,17,2a',    os='ubuntu-20.04', stdlib='libc++', install='libc++-9-dev libc++abi-9-dev'),
+    job(compiler='clang-10',  cxxstd='11,14,17,20',    os='ubuntu-20.04', stdlib='libc++', install='libc++-10-dev libc++abi-10-dev'),
+    job(compiler='clang-11',  cxxstd='11,14,17,20',    os='ubuntu-20.04', stdlib='libc++', install='libc++-11-dev libc++abi-11-dev'),
+    job(compiler='clang-12',  cxxstd='11,14,17,20',    os='ubuntu-22.04', stdlib='libc++', install='libc++-12-dev libc++abi-12-dev libunwind-12-dev'),
+    job(compiler='clang-13',  cxxstd='11,14,17,20',    os='ubuntu-22.04', stdlib='libc++', install='libc++-13-dev libc++abi-13-dev'),
+    job(compiler='clang-14',  cxxstd='11,14,17,20',    os='ubuntu-22.04', stdlib='libc++', install='libc++-14-dev libc++abi-14-dev'),
+    job(compiler='clang-15',  cxxstd='11,14,17,20',    os='ubuntu-22.04', stdlib='libc++', install='libc++-15-dev libc++abi-15-dev', add_llvm=True),

-  # Oldest compilers
-  linux_cxx("GCC 4.8: C++11", "g++-4.8", packages="g++-4.8", buildscript="drone", buildtype="boost", image="cppalliance/droneubuntu1604:1", environment={'B2_TOOLSET': 'gcc-4.8', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '11'}, globalenv=globalenv),
-  linux_cxx("GCC 4.8: C++11 Standalone", "g++-4.8", packages="g++-4.8", buildscript="drone", buildtype="boost", image="cppalliance/droneubuntu1604:1", environment={'B2_TOOLSET': 'gcc-4.8', 'B2_CXXFLAGS': '-Werror', 'B2_DEFINES': 'define=BOOST_STATIC_STRING_STANDALONE', 'B2_CXXSTD': '11'}, globalenv=globalenv),
-  linux_cxx("Clang 3.8: C++11", "clang++-3.8", packages="clang-3.8", buildscript="drone", buildtype="boost", image="cppalliance/droneubuntu1604:1", environment={'B2_VARIANT': 'debug', 'B2_CXXFLAGS': '-Werror', 'B2_TOOLSET': 'clang-3.8', 'B2_CXXSTD': '11'}, globalenv=globalenv),
-  linux_cxx("Clang 3.8: C++11 Standalone", "clang++-3.8", packages="clang-3.8", buildscript="drone", buildtype="boost", image="cppalliance/droneubuntu1604:1", environment={'B2_VARIANT': 'debug', 'B2_CXXFLAGS': '-Werror', 'B2_TOOLSET': 'clang-3.8', 'B2_DEFINES': 'define=BOOST_STATIC_STRING_STANDALONE', 'B2_CXXSTD': '11'}, globalenv=globalenv),
-
-  # Sanitizers + Valgrind
-  linux_cxx("ASan", "g++-12", packages="g++-12", buildscript="drone", buildtype="boost", image="cppalliance/droneubuntu2204:1", environment={'COMMENT': 'asan', 'B2_VARIANT': 'debug', 'B2_TOOLSET': 'gcc-12', 'B2_CXXSTD': '11,14,17', 'B2_ASAN': '1', 'B2_DEFINES': 'BOOST_NO_STRESS_TEST=1', 'DRONE_EXTRA_PRIVILEGED': 'True'}, globalenv=globalenv, privileged=True),
-  linux_cxx("TSan", "g++-12", packages="g++-12", buildscript="drone", buildtype="boost", image="cppalliance/droneubuntu2204:1", environment={'COMMENT': 'tsan', 'B2_VARIANT': 'debug', 'B2_TOOLSET': 'gcc-12', 'B2_CXXSTD': '11,14,17', 'B2_TSAN': '1', 'B2_DEFINES': 'BOOST_NO_STRESS_TEST=1'}, globalenv=globalenv),
-  linux_cxx("UBSan", "g++-12", packages="g++-12", buildscript="drone", buildtype="boost", image="cppalliance/droneubuntu2204:1", environment={'COMMENT': 'ubsan', 'B2_VARIANT': 'debug', 'B2_TOOLSET': 'gcc-12', 'B2_CXXSTD': '11,14,17', 'B2_UBSAN': '1', 'B2_DEFINES': 'define=BOOST_NO_STRESS_TEST=1', 'B2_LINKFLAGS': '-fuse-ld=gold'}, globalenv=globalenv),
-  linux_cxx("Valgrind", "clang++-14", packages="clang-14 libc6-dbg libc++-dev libstdc++-9-dev", llvm_os="jammy", llvm_ver="14", buildscript="drone", buildtype="valgrind", image="cppalliance/droneubuntu2204:1", environment={'COMMENT': 'valgrind', 'B2_TOOLSET': 'clang-14', 'B2_CXXSTD': '11,14,17', 'B2_DEFINES': 'BOOST_NO_STRESS_TEST=1', 'B2_VARIANT': 'debug', 'B2_TESTFLAGS': 'testing.launcher=valgrind', 'VALGRIND_OPTS': '--error-exitcode=1'}, globalenv=globalenv),
-
-  # arm64 (unsigned char)
-  linux_cxx("ARM64: GCC 11", "g++-11", packages="g++-11", buildscript="drone", buildtype="boost", image="cppalliance/droneubuntu2004:multiarch", environment={'B2_TOOLSET': 'gcc-11', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '17,20'}, arch="arm64", globalenv=globalenv),
-
-  # s390x
-  linux_cxx("S390x: Clang 12", "clang++-12", packages="clang-12 libstdc++-9-dev", llvm_os="focal", llvm_ver="12", buildtype="boost", buildscript="drone", image="cppalliance/droneubuntu2004:multiarch", environment={'B2_TOOLSET': 'clang-12', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '17,20'}, arch="s390x", globalenv=globalenv),
-
-  # Documentation
-  # linux_cxx("Docs", "g++", packages="docbook docbook-xml docbook-xsl xsltproc libsaxonhe-java default-jre-headless flex libfl-dev bison unzip rsync", buildtype="docs", buildscript="drone", image="cppalliance/droneubuntu1804:1", environment={'COMMENT': 'docs'}, globalenv=globalenv),
-
-  # CMake tests (https://github.com/boostorg/boost-ci)
-  ## Compiling as part of the boost superproject
-  linux_cxx("CMake Superproject", "g++", packages="", buildscript="drone", buildtype="cmake-superproject", image="cppalliance/droneubuntu1804:1", globalenv=globalenv),
-  ## Installing
-  # linux_cxx("CMake Install", "g++", packages="", buildscript="drone", buildtype="cmake1", image="cppalliance/droneubuntu1804:1", environment={'CMAKE_INSTALL_TEST': '1'}, globalenv=globalenv),
-
-  # ------------------------------------------------------------------
-
-  # OSX
-  osx_cxx("OSX: Clang", "g++", packages="", buildscript="drone", buildtype="boost", xcode_version="13.4.1", environment={'B2_TOOLSET': 'clang', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '11,17'}, globalenv=globalenv),
-
-  # GCC (All other versions)
-  linux_cxx("GCC 4.9: C++11", "g++-4.9", packages="g++-4.9", buildscript="drone", buildtype="boost", image="cppalliance/droneubuntu1604:1", environment={'B2_TOOLSET': 'gcc-4.9', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '11'}, globalenv=globalenv),
-  linux_cxx("GCC 5: C++11", "g++-5", packages="g++-5", buildscript="drone", buildtype="boost", image=linuxglobalimage, environment={'B2_TOOLSET': 'gcc-5', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '11'}, globalenv=globalenv),
-  linux_cxx("GCC 6: C++11,14", "g++-6", packages="g++-6", buildscript="drone", buildtype="boost", image=linuxglobalimage, environment={'B2_TOOLSET': 'gcc-6', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '11,14'}, globalenv=globalenv),
-  linux_cxx("GCC 7: C++14,17", "g++-7", packages="g++-7", buildscript="drone", buildtype="boost", image=linuxglobalimage, environment={'B2_TOOLSET': 'gcc-7', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '14,17'}, globalenv=globalenv),
-  linux_cxx("GCC 8: C++17", "g++-8", packages="g++-8", buildscript="drone", buildtype="boost", image=linuxglobalimage, environment={'B2_TOOLSET': 'gcc-8', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '17'}, globalenv=globalenv),
-  linux_cxx("GCC 9: C++17", "g++-9", packages="g++-9", buildscript="drone", buildtype="boost", image=linuxglobalimage, environment={'B2_TOOLSET': 'gcc-9', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '17'}, globalenv=globalenv),
-  linux_cxx("GCC 10: C++17", "g++-10", packages="g++-10", buildscript="drone", buildtype="boost", image=linuxglobalimage, environment={'B2_TOOLSET': 'gcc-10', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '17'}, globalenv=globalenv),
-  linux_cxx("GCC 11: C++17,20", "g++-11", packages="g++-11", buildscript="drone", buildtype="boost", image=linuxglobalimage, environment={'B2_TOOLSET': 'gcc-11', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '17,20'}, globalenv=globalenv),
-
-  # Clang (All other versions)
-  linux_cxx("Clang 4.0: C++11,14", "clang++-4.0", packages="clang-4.0 libstdc++-6-dev", llvm_os="xenial", llvm_ver="4.0", buildscript="drone", buildtype="boost", image="cppalliance/droneubuntu1804:1", environment={'B2_TOOLSET': 'clang-4.0', 'B2_CXXFLAGS': '', 'B2_CXXSTD': '11,14'}, globalenv=globalenv),
-  linux_cxx("Clang 5.0: C++11,14", "clang++-5.0", packages="clang-5.0 libstdc++-7-dev", llvm_os="bionic", llvm_ver="5.0", buildscript="drone", buildtype="boost", image=linuxglobalimage, environment={'B2_TOOLSET': 'clang-5.0', 'B2_CXXFLAGS': '', 'B2_CXXSTD': '11,14'}, globalenv=globalenv),
-  linux_cxx("Clang 6.0: C++11,14", "clang++-6.0", packages="clang-6.0 libc6-dbg libc++-dev libc++abi-dev libstdc++-8-dev", llvm_os="bionic", llvm_ver="6.0", buildscript="drone", buildtype="boost", image=linuxglobalimage, environment={'B2_TOOLSET': 'clang-6.0', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '11,14', 'B2_STDLIB': 'libc++'}, globalenv=globalenv),
-  linux_cxx("Clang 6.0: C++14,17", "clang++-6.0", packages="clang-6.0 libc6-dbg libc++-dev libc++abi-dev libstdc++-8-dev", llvm_os="bionic", llvm_ver="6.0", buildscript="drone", buildtype="boost", image=linuxglobalimage, environment={'B2_TOOLSET': 'clang-6.0', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '14,17'}, globalenv=globalenv),
-  linux_cxx("Clang 7: C++17", "clang++-7", packages="clang-7 libc6-dbg libc++-dev libstdc++-8-dev", llvm_os="bionic", llvm_ver="7", buildscript="drone", buildtype="boost", image=linuxglobalimage, environment={'B2_TOOLSET': 'clang-7', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '17'}, globalenv=globalenv),
-  linux_cxx("Clang 8: C++17", "clang++-8", packages="clang-8 libc6-dbg libc++-dev libstdc++-8-dev", llvm_os="bionic", llvm_ver="8", buildscript="drone", buildtype="boost", image=linuxglobalimage, environment={'B2_TOOLSET': 'clang-8', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '17'}, globalenv=globalenv),
-  linux_cxx("Clang 9: C++14,17", "clang++-9", packages="clang-9 libstdc++-9-dev", llvm_os="bionic", llvm_ver="9", buildscript="drone", buildtype="boost", image=linuxglobalimage, environment={'B2_TOOLSET': 'clang-9', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '14,17'}, globalenv=globalenv),
-  linux_cxx("Clang 10: C++14,17", "clang++-10", packages="clang-10 libstdc++-9-dev", llvm_os="focal", llvm_ver="10", buildscript="drone", buildtype="boost", image="cppalliance/droneubuntu2004:1", environment={'B2_TOOLSET': 'clang-10', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '14,17'}, globalenv=globalenv),
-  linux_cxx("Clang 11: C++14,17", "clang++-11", packages="clang-11 libstdc++-9-dev", llvm_os="focal", llvm_ver="11", buildscript="drone", buildtype="boost", image="cppalliance/droneubuntu2004:1", environment={'B2_TOOLSET': 'clang-11', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '14,17'}, globalenv=globalenv),
-  linux_cxx("Clang 12: C++17,20", "clang++-12", packages="clang-12 libstdc++-9-dev", llvm_os="focal", llvm_ver="12", buildscript="drone", buildtype="boost", image="cppalliance/droneubuntu2004:1", environment={'B2_TOOLSET': 'clang-12', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '17,20'}, globalenv=globalenv),
-  linux_cxx("Clang 13: C++17,20", "clang++-13", packages="clang-13 libstdc++-10-dev", llvm_os="jammy", llvm_ver="13", buildscript="drone", buildtype="boost", image="cppalliance/droneubuntu2204:1", environment={'B2_TOOLSET': 'clang-13', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '17,20'}, globalenv=globalenv),
-  linux_cxx("Clang 14: C++17,20", "clang++-14", packages="clang-14 libstdc++-10-dev", llvm_os="jammy", llvm_ver="14", buildscript="drone", buildtype="boost", image="cppalliance/droneubuntu2204:1", environment={'B2_TOOLSET': 'clang-14', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '17,20'}, globalenv=globalenv),
-
-  # arm64 (unsigned char)
-  linux_cxx("ARM64: Clang 12", "clang++-12", packages="clang-12 libstdc++-9-dev", llvm_os="focal", llvm_ver="12", buildscript="drone", buildtype="boost", image="cppalliance/droneubuntu2004:multiarch", environment={'B2_TOOLSET': 'clang-12', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '11,14,17,20'}, arch="arm64", globalenv=globalenv),
-
-  # s390x
-  linux_cxx("S390x: GCC 11", "g++-11", packages="g++-11", buildtype="boost", buildscript="drone", image="cppalliance/droneubuntu2004:multiarch", environment={'B2_TOOLSET': 'gcc-11', 'B2_CXXFLAGS': '-Werror', 'B2_CXXSTD': '17'}, arch="s390x", globalenv=globalenv),
-
-  # MSVC
-  windows_cxx("MSVC 14.1", "", image="cppalliance/dronevs2017", buildtype="boost", buildscript="drone", environment={"B2_TOOLSET": "msvc-14.1", 'B2_CXXFLAGS': '/WX', "B2_CXXSTD": "11,14,17"},globalenv=globalenv),
-  windows_cxx("MSVC 14.2: C++14,17,latest", "", image="cppalliance/dronevs2019", buildtype="boost", buildscript="drone", environment={"B2_TOOLSET": "msvc-14.2", 'B2_CXXFLAGS': '/WX', "B2_CXXSTD": "14,17,latest"},globalenv=globalenv),
-  windows_cxx("MSVC 14.3: C++17,20", "", image="cppalliance/dronevs2022", buildtype="boost", buildscript="drone", environment={"B2_TOOLSET": "msvc-14.3", 'B2_CXXFLAGS': '/WX', "B2_CXXSTD": "17,20"},globalenv=globalenv),
-]
+    # FreeBSD
+    job(compiler='clang-10',  cxxstd='11,14,17,20',    os='freebsd-13.1'),
+    job(compiler='clang-15',  cxxstd='11,14,17,20',    os='freebsd-13.1'),
+    job(compiler='gcc-11',    cxxstd='11,14,17,20',    os='freebsd-13.1', linkflags='-Wl,-rpath=/usr/local/lib/gcc11'),
+    # OSX
+    job(compiler='clang',     cxxstd='11,14,17,2a',    os='osx-xcode-10.1'),
+    job(compiler='clang',     cxxstd='11,14,17,2a',    os='osx-xcode-10.3'),
+    job(compiler='clang',     cxxstd='11,14,17,2a',    os='osx-xcode-11.1'),
+    job(compiler='clang',     cxxstd='11,14,17,2a',    os='osx-xcode-11.7'),
+    job(compiler='clang',     cxxstd='11,14,17,2a',    os='osx-xcode-12'),
+    job(compiler='clang',     cxxstd='11,14,17,20',    os='osx-xcode-12.5.1'),
+    job(compiler='clang',     cxxstd='11,14,17,20',    os='osx-xcode-13.0'),
+    job(compiler='clang',     cxxstd='11,14,17,20',    os='osx-xcode-13.4.1'),
+    job(compiler='clang',     cxxstd='11,14,17,20,2b', os='osx-xcode-14.0'),
+    job(compiler='clang',     cxxstd='11,14,17,20,2b', os='osx-xcode-14.3.1'),
+    job(compiler='clang',     cxxstd='11,14,17,20,2b', os='osx-xcode-15.0.1'),
+    # ARM64
+    job(compiler='clang-12',  cxxstd='11,14,17,20',    os='ubuntu-20.04', arch='arm64', add_llvm=True),
+    job(compiler='gcc-11',    cxxstd='11,14,17,20',    os='ubuntu-20.04', arch='arm64'),
+    # S390x
+    job(compiler='clang-12',  cxxstd='11,14,17,20',    os='ubuntu-20.04', arch='s390x', add_llvm=True),
+    job(compiler='gcc-11',    cxxstd='11,14,17,20',    os='ubuntu-20.04', arch='s390x'),
+    # Windows
+    job(compiler='msvc-14.0', cxxstd=None,              os='windows', env={'B2_DONT_EMBED_MANIFEST': 1}),
+    job(compiler='msvc-14.1', cxxstd=None,              os='windows'),
+    job(compiler='msvc-14.2', cxxstd=None,              os='windows'),
+    job(compiler='msvc-14.3', cxxstd=None,              os='windows'),
+    job(compiler='msvc-14.0', cxxstd='14,17,20',        os='windows', env={'B2_DONT_EMBED_MANIFEST': 1}),
+    job(compiler='msvc-14.1', cxxstd='14,17,20',        os='windows'),
+    job(compiler='msvc-14.2', cxxstd='14,17,20',        os='windows'),
+    job(compiler='msvc-14.3', cxxstd='14,17,20,latest', os='windows'),
+  ]

 # from https://github.com/boostorg/boost-ci
-load("@boost_ci//ci/drone/:functions.star", "linux_cxx","windows_cxx","osx_cxx","freebsd_cxx")
+load("@boost_ci//ci/drone/:functions.star", "linux_cxx", "windows_cxx", "osx_cxx", "freebsd_cxx", "job_impl")
--- a/.drone/codecov_coveralls.sh
+++ b/.drone/codecov_coveralls.sh
@@ -0,0 +1,28 @@
+#!/bin/bash
+
+# Copyright 2020 Rene Rivera, Sam Darwin
+# Copyright 2025 Alexander Grund
+# Distributed under the Boost Software License, Version 1.0.
+# (See accompanying file LICENSE.txt or copy at http://boost.org/LICENSE_1_0.txt)
+
+
+set -xe
+
+# Run the regular Boost CI script which does the test & upload to codecov.io
+wget https://github.com/boostorg/boost-ci/raw/refs/heads/master/.drone/drone.sh
+. drone.sh
+
+# coveralls
+# uses multiple lcov steps from boost-ci codecov.sh script
+if [ -n "${COVERALLS_REPO_TOKEN}" ]; then
+    echo "processing coveralls"
+    pip3 install --user cpp-coveralls
+    cd "$BOOST_CI_SRC_FOLDER"
+
+    export PATH=/tmp/lcov/bin:$PATH
+    command -v lcov
+    lcov --version
+
+    lcov --remove coverage.info -o coverage_filtered.info '*/test/*' '*/extra/*'
+    cpp-coveralls --verbose -l coverage_filtered.info
+fi
--- a/.drone/drone.bat
+++ b/.drone/drone.bat
@@ -1,31 +0,0 @@
-
-@ECHO ON
-setlocal enabledelayedexpansion
-
-if "%DRONE_JOB_BUILDTYPE%" == "boost" (
-
-echo '==================================> INSTALL'
-
-git clone https://github.com/boostorg/boost-ci.git boost-ci-cloned --depth 1
-cp -prf boost-ci-cloned/ci .
-rm -rf boost-ci-cloned
-REM source ci/travis/install.sh
-REM The contents of install.sh below:
-
-for /F %%i in ("%DRONE_REPO%") do @set SELF=%%~nxi
-SET BOOST_CI_TARGET_BRANCH=%DRONE_COMMIT_BRANCH%
-SET BOOST_CI_SRC_FOLDER=%cd%
-
-call ci\common_install.bat
-
-echo '==================================> COMPILE'
-
-REM set B2_TARGETS=libs/!SELF!/test libs/!SELF!/example
-set B2_TARGETS=libs/!SELF!/test
-call !BOOST_ROOT!\libs\!SELF!\ci\build.bat
-
-) else if "%DRONE_JOB_BUILDTYPE%" == "standalone-windows" (
-
-REM not used
-
-)
--- a/.drone/drone.sh
+++ b/.drone/drone.sh
@@ -1,236 +0,0 @@
-#!/bin/bash
-
-# Copyright 2020 Rene Rivera, Sam Darwin
-# Distributed under the Boost Software License, Version 1.0.
-# (See accompanying file LICENSE.txt or copy at http://boost.org/LICENSE_1_0.txt)
-
-set -xe
-
-export TRAVIS_BUILD_DIR=$(pwd)
-export DRONE_BUILD_DIR=$(pwd)
-export TRAVIS_BRANCH=$DRONE_BRANCH
-export TRAVIS_EVENT_TYPE=$DRONE_BUILD_EVENT
-export VCS_COMMIT_ID=$DRONE_COMMIT
-export GIT_COMMIT=$DRONE_COMMIT
-export REPO_NAME=$DRONE_REPO
-export USER=$(whoami)
-export CC=${CC:-gcc}
-export PATH=~/.local/bin:/usr/local/bin:$PATH
-
-common_install() {
-  git clone https://github.com/boostorg/boost-ci.git boost-ci-cloned --depth 1
-  cp -prf boost-ci-cloned/ci .
-  rm -rf boost-ci-cloned
-
-  if [ "$TRAVIS_OS_NAME" == "osx" ]; then
-    unset -f cd
-  fi
-
-  export SELF=$(basename $REPO_NAME)
-  export BOOST_CI_TARGET_BRANCH="$TRAVIS_BRANCH"
-  export BOOST_CI_SRC_FOLDER=$(pwd)
-
-  . ./ci/common_install.sh
-}
-
-if [ "$DRONE_JOB_BUILDTYPE" == "boost" ]; then
-
-  echo '==================================> INSTALL'
-
-  common_install
-
-  echo '==================================> SCRIPT'
-
-  export B2_TARGETS=${B2_TARGETS:-"libs/$SELF/test"}
-  $BOOST_ROOT/libs/$SELF/ci/travis/build.sh
-
-elif [ "$DRONE_JOB_BUILDTYPE" == "docs" ]; then
-
-  echo '==================================> INSTALL'
-
-  export SELF=$(basename $REPO_NAME)
-
-  pwd
-  cd ..
-  mkdir -p $HOME/cache && cd $HOME/cache
-  if [ ! -d doxygen ]; then git clone -b 'Release_1_8_15' --depth 1 https://github.com/doxygen/doxygen.git && echo "not-cached"; else echo "cached"; fi
-  cd doxygen
-  cmake -H. -Bbuild -DCMAKE_BUILD_TYPE=Release
-  cd build
-  sudo make install
-  cd ../..
-  if [ ! -f saxonhe.zip ]; then wget -O saxonhe.zip https://sourceforge.net/projects/saxon/files/Saxon-HE/9.9/SaxonHE9-9-1-4J.zip/download && echo "not-cached"; else echo "cached"; fi
-  unzip -o saxonhe.zip
-  sudo rm /usr/share/java/Saxon-HE.jar
-  sudo cp saxon9he.jar /usr/share/java/Saxon-HE.jar
-  cd ..
-  BOOST_BRANCH=develop && [ "$TRAVIS_BRANCH" == "master" ] && BOOST_BRANCH=master || true
-  git clone -b $BOOST_BRANCH https://github.com/boostorg/boost.git boost-root --depth 1
-  cd boost-root
-  export BOOST_ROOT=$(pwd)
-  git submodule update --init libs/context
-  git submodule update --init tools/boostbook
-  git submodule update --init tools/boostdep
-  git submodule update --init tools/docca
-  git submodule update --init tools/quickbook
-  rsync -av $TRAVIS_BUILD_DIR/ libs/$SELF
-  python tools/boostdep/depinst/depinst.py ../tools/quickbook
-  ./bootstrap.sh
-  ./b2 headers
-
-  echo '==================================> SCRIPT'
-
-  echo "using doxygen ; using boostbook ; using saxonhe ;" >tools/build/src/user-config.jam
-  ./b2 -j3 libs/$SELF/doc//boostrelease
-
-elif [ "$DRONE_JOB_BUILDTYPE" == "codecov" ]; then
-
-  echo '==================================> INSTALL'
-
-  common_install
-
-  echo '==================================> SCRIPT'
-
-  set +e
-
-  cd $BOOST_ROOT/libs/$SELF
-  ci/travis/codecov.sh
-
-  # coveralls
-  # uses multiple lcov steps from boost-ci codecov.sh script
-  if [ -n "${COVERALLS_REPO_TOKEN}" ]; then
-    echo "processing coveralls"
-    pip3 install --user cpp-coveralls
-    cd $BOOST_CI_SRC_FOLDER
-
-    export PATH=/tmp/lcov/bin:$PATH
-    command -v lcov
-    lcov --version
-
-    lcov --remove coverage.info -o coverage_filtered.info '*/test/*' '*/extra/*'
-    cpp-coveralls --verbose -l coverage_filtered.info
-  fi
-
-elif [ "$DRONE_JOB_BUILDTYPE" == "valgrind" ]; then
-
-  echo '==================================> INSTALL'
-
-  common_install
-
-  echo '==================================> SCRIPT'
-
-  cd $BOOST_ROOT/libs/$SELF
-  ci/travis/valgrind.sh
-
-elif [ "$DRONE_JOB_BUILDTYPE" == "standalone" ]; then
-
-  echo '==================================> INSTALL'
-
-  # Installing cmake with apt-get, so not required here:
-  # pip install --user cmake
-
-  echo '==================================> SCRIPT'
-
-  export CXXFLAGS="-Wall -Wextra -Werror -std=c++17"
-  mkdir __build_17
-  cd __build_17
-  cmake -DBOOST_JSON_STANDALONE=1 ..
-  cmake --build .
-  ctest -V .
-  export CXXFLAGS="-Wall -Wextra -Werror -std=c++2a"
-  mkdir ../__build_2a
-  cd ../__build_2a
-  cmake -DBOOST_JSON_STANDALONE=1 ..
-  cmake --build .
-  ctest -V .
-
-elif [ "$DRONE_JOB_BUILDTYPE" == "coverity" ]; then
-
-  echo '==================================> INSTALL'
-
-  common_install
-
-  echo '==================================> SCRIPT'
-
-  if [ -n "${COVERITY_SCAN_NOTIFICATION_EMAIL}" -a \( "$TRAVIS_BRANCH" = "develop" -o "$TRAVIS_BRANCH" = "master" \) -a \( "$DRONE_BUILD_EVENT" = "push" -o "$DRONE_BUILD_EVENT" = "cron" \) ]; then
-    cd $BOOST_ROOT/libs/$SELF
-    ci/travis/coverity.sh
-  fi
-
-elif [ "$DRONE_JOB_BUILDTYPE" == "cmake-superproject" ]; then
-
-  echo '==================================> INSTALL'
-
-  common_install
-
-  echo '==================================> COMPILE'
-
-  # May want to re-enable -Werror
-  # export CXXFLAGS="-Wall -Wextra -Werror"
-  export CXXFLAGS="-Wall -Wextra"
-
-  mkdir __build_static
-  cd __build_static
-  cmake -DBOOST_ENABLE_CMAKE=1 -DBUILD_TESTING=ON -DBoost_VERBOSE=1 \
-    -DBOOST_INCLUDE_LIBRARIES=$SELF ..
-  cmake --build .
-  ctest --output-on-failure -R boost_$SELF
-
-  cd ..
-
-  mkdir __build_shared
-  cd __build_shared
-  cmake -DBOOST_ENABLE_CMAKE=1 -DBUILD_TESTING=ON -DBoost_VERBOSE=1 \
-    -DBOOST_INCLUDE_LIBRARIES=$SELF -DBUILD_SHARED_LIBS=ON ..
-  cmake --build .
-  ctest --output-on-failure -R boost_$SELF
-
-elif [ "$DRONE_JOB_BUILDTYPE" == "cmake1" ]; then
-
-  echo '==================================> INSTALL'
-
-  # https://github.com/opencv/opencv-python#frequently-asked-questions
-  pip install --upgrade pip
-  pip install --user cmake
-
-  echo '==================================> SCRIPT'
-
-  export SELF=$(basename $REPO_NAME)
-  BOOST_BRANCH=develop && [ "$DRONE_BRANCH" == "master" ] && BOOST_BRANCH=master || true
-  echo BOOST_BRANCH: $BOOST_BRANCH
-  cd ..
-  git clone -b $BOOST_BRANCH --depth 1 https://github.com/boostorg/boost.git boost-root
-  cd boost-root
-  # mkdir -p libs/$SELF
-  # cp -r $DRONE_BUILD_DIR/* libs/$SELF
-  # git submodule update --init tools/boostdep
-  git submodule update --init --recursive
-  mkdir -p libs/$SELF
-  cp -r $DRONE_BUILD_DIR/* libs/$SELF
-
-  # CMake tests
-  cd libs/$SELF
-  mkdir __build__ && cd __build__
-  cmake -DCMAKE_INSTALL_PREFIX=~/.local ..
-  cmake --build . --target install
-  ctest --output-on-failure
-
-  # CMake subdir tests
-  cd ../test/cmake_test && mkdir __build__ && cd __build__
-  cmake -DCMAKE_INSTALL_PREFIX=~/.local ..
-  cmake --build .
-  cmake --build . --target check
-  ctest --output-on-failure
-
-  # Install Library
-  cd ../../../../.. && mkdir __build_cmake_install_test__ && cd __build_cmake_install_test__
-  cmake -DBOOST_INCLUDE_LIBRARIES=$SELF -DCMAKE_INSTALL_PREFIX=~/.local -DBoost_VERBOSE=ON -DBoost_DEBUG=ON ..
-  cmake --build . --target install
-
-  # CMake install tests
-  cd ../libs/$SELF/test/cmake_test && mkdir __build_cmake_install_test__ && cd __build_cmake_install_test__
-  cmake -DBOOST_CI_INSTALL_TEST=ON -DCMAKE_PREFIX_PATH=~/.local ..
-  cmake --build .
-  ctest --output-on-failure
-
-fi
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -37,7 +37,7 @@ jobs:
    name: Run Boost.CI
    uses: boostorg/boost-ci/.github/workflows/reusable.yml@master
    with:
-      exclude_cxxstd: '98,03,0x,2c,26'
+      exclude_cxxstd: '98,03,0x'
      enable_pr_coverage: false
      enable_multiarch: false
    # Example of customization:
--- a/.github/workflows/example.yml
+++ b/.github/workflows/example.yml
@@ -0,0 +1,156 @@
+#
+# Copyright (c) 2025 Gennaro Prota (gennaro dot prota at gmail dot com)
+#
+# Distributed under the Boost Software License, Version 1.0. (See accompanying
+# file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
+#
+# Official repository: https://github.com/boostorg/static_string
+#
+
+name: Example (basic_static_cstring)
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+      - develop
+      - bugfix/**
+      - feature/**
+      - fix/**
+      - github/**
+      - pr/**
+    paths-ignore:
+      - LICENSE
+      - meta/**
+      - README.md
+
+jobs:
+  linux:
+    runs-on: ubuntu-24.04
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - { toolset: gcc-13,   cxxstd: '20,23' }
+          - { toolset: gcc-14,   cxxstd: '20,23,26' }
+          - { toolset: clang-17, cxxstd: '20,23' }
+          - { toolset: clang-18, cxxstd: '20,23,26' }
+
+    steps:
+      - name: Checkout Boost super-project
+        uses: actions/checkout@v4
+        with:
+          repository: boostorg/boost
+          ref: develop
+          fetch-depth: 0
+
+      - name: Checkout this library
+        uses: actions/checkout@v4
+        with:
+          path: libs/static_string
+          fetch-depth: 0
+
+      - name: Initialize Boost submodules
+        run: |
+          git submodule update --init tools/boostdep
+          python tools/boostdep/depinst/depinst.py --git_args '--jobs 4' static_string
+
+      - name: Bootstrap b2
+        run: ./bootstrap.sh
+
+      - name: Generate Boost headers
+        run: ./b2 headers
+
+      - name: Build and run example tests
+        run: |
+          ./b2 libs/static_string/example/static_cstring \
+            toolset=${{ matrix.toolset }} \
+            cxxstd=${{ matrix.cxxstd }} \
+            variant=debug,release \
+            -j$(nproc)
+
+  macos:
+    runs-on: macos-14
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - { toolset: clang, cxxstd: '20,23' }
+
+    steps:
+      - name: Checkout Boost super-project
+        uses: actions/checkout@v4
+        with:
+          repository: boostorg/boost
+          ref: develop
+          fetch-depth: 0
+
+      - name: Checkout this library
+        uses: actions/checkout@v4
+        with:
+          path: libs/static_string
+          fetch-depth: 0
+
+      - name: Initialize Boost submodules
+        run: |
+          git submodule update --init tools/boostdep
+          python3 tools/boostdep/depinst/depinst.py --git_args '--jobs 4' static_string
+
+      - name: Bootstrap b2
+        run: ./bootstrap.sh
+
+      - name: Generate Boost headers
+        run: ./b2 headers
+
+      - name: Build and run example tests
+        run: |
+          ./b2 libs/static_string/example/static_cstring \
+            toolset=${{ matrix.toolset }} \
+            cxxstd=${{ matrix.cxxstd }} \
+            variant=debug,release \
+            -j$(sysctl -n hw.ncpu)
+
+  windows:
+    runs-on: windows-2022
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - { toolset: msvc-14.3, cxxstd: '20,latest' }
+
+    steps:
+      - name: Checkout Boost super-project
+        uses: actions/checkout@v4
+        with:
+          repository: boostorg/boost
+          ref: develop
+          fetch-depth: 0
+
+      - name: Checkout this library
+        uses: actions/checkout@v4
+        with:
+          path: libs/static_string
+          fetch-depth: 0
+
+      - name: Initialize Boost submodules
+        run: |
+          git submodule update --init tools/boostdep
+          python tools/boostdep/depinst/depinst.py --git_args '--jobs 4' static_string
+
+      - name: Bootstrap b2
+        run: .\bootstrap.bat
+        shell: cmd
+
+      - name: Generate Boost headers
+        run: .\b2 headers
+        shell: cmd
+
+      - name: Build and run example tests
+        run: |
+          .\b2 libs/static_string/example/static_cstring ^
+            toolset=${{ matrix.toolset }} ^
+            cxxstd=${{ matrix.cxxstd }} ^
+            variant=debug,release ^
+            address-model=64
+        shell: cmd
--- a/.gitignore
+++ b/.gitignore
@@ -1,8 +1,15 @@
 bin/
 bin64/
+build/

 # Because of CMake and VS2017
 Win32/
 x64/
 .vs/
-out/
+out/
+
+# VS CMake settings
+/CMakeSettings.json
+# CMake presets
+/CMakePresets.json
+/CMakeUserPresets.json
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -7,7 +7,7 @@
 # Official repository: https://github.com/boostorg/static_string
 #

-cmake_minimum_required(VERSION 3.5...3.16)
+cmake_minimum_required(VERSION 3.8...3.16)

 project(boost_static_string VERSION "${BOOST_SUPERPROJECT_VERSION}" LANGUAGES CXX)

@@ -45,7 +45,7 @@ if (BOOST_STATIC_STRING_FIND_PACKAGE_BOOST)
    find_package(Boost 1.78.0 REQUIRED COMPONENTS container)
 elseif (BOOST_STATIC_STRING_IS_ROOT)
    set(BOOST_STATIC_STRING_UNIT_TEST_LIBRARIES core)
-    set(BOOST_INCLUDE_LIBRARIES static_string assert container_hash static_assert throw_exception utility ${BOOST_STATIC_STRING_UNIT_TEST_LIBRARIES})
+    set(BOOST_INCLUDE_LIBRARIES static_string assert container_hash throw_exception utility ${BOOST_STATIC_STRING_UNIT_TEST_LIBRARIES})
    set(BOOST_EXCLUDE_LIBRARIES static_string)
    set(CMAKE_FOLDER Dependencies)
    add_subdirectory(../.. Dependencies/boost EXCLUDE_FROM_ALL)
@@ -90,7 +90,6 @@ else ()
            Boost::assert
            Boost::container_hash
            Boost::core
-            Boost::static_assert
            Boost::throw_exception
            Boost::utility
            )
--- a/README.md
+++ b/README.md
@@ -1,9 +1,9 @@
 # Boost.StaticString

-Branch          | Travis | Appveyor | Azure Pipelines | codecov.io | Docs | Matrix |
+Branch          | GHA CI | Appveyor | Azure Pipelines | codecov.io | Docs | Matrix |
 :-------------: | ------ | -------- | --------------- | ---------- | ---- | ------ |
-[`master`](https://github.com/boostorg/static_string/tree/master) | [![Build Status](https://travis-ci.org/boostorg/static_string.svg?branch=master)](https://travis-ci.org/boostorg/static_string) | [![Build status](https://ci.appveyor.com/api/projects/status/64es4wg4w7mc5wn2/branch/master?svg=true)](https://ci.appveyor.com/project/sdkrystian/static-string/branch/master) | [![Build Status](https://krystiands.visualstudio.com/static_string/_apis/build/status/Boost.StaticString?branchName=master)](https://krystiands.visualstudio.com/static_string/_build/latest?definitionId=3&branchName=master) | [![codecov](https://codecov.io/gh/boostorg/static_string/branch/master/graph/badge.svg)](https://codecov.io/gh/boostorg/static_string/branch/master) | [![Documentation](https://img.shields.io/badge/docs-master-brightgreen.svg)](http://www.boost.org/doc/libs/release/libs/static_string) | [![Matrix](https://img.shields.io/badge/matrix-master-brightgreen.svg)](http://www.boost.org/development/tests/master/developer/static_string.html)
-[`develop`](https://github.com/boostorg/static_string/tree/develop) | [![Build Status](https://travis-ci.org/boostorg/static_string.svg?branch=develop)](https://travis-ci.org/boostorg/static_string) | [![Build status](https://ci.appveyor.com/api/projects/status/64es4wg4w7mc5wn2/branch/develop?svg=true)](https://ci.appveyor.com/project/sdkrystian/static-string/branch/develop) | [![Build Status](https://krystiands.visualstudio.com/static_string/_apis/build/status/Boost.StaticString?branchName=develop)](https://krystiands.visualstudio.com/static_string/_build/latest?definitionId=3&branchName=develop) | [![codecov](https://codecov.io/gh/boostorg/static_string/branch/develop/graph/badge.svg)](https://codecov.io/gh/boostorg/static_string/branch/develop) | [![Documentation](https://img.shields.io/badge/docs-develop-brightgreen.svg)](http://www.boost.org/doc/libs/develop/libs/static_string) | [![Matrix](https://img.shields.io/badge/matrix-develop-brightgreen.svg)](http://www.boost.org/development/tests/develop/developer/static_string.html)
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 ## Introduction

--- a/build.jam
+++ b/build.jam
@@ -10,7 +10,6 @@ constant boost_dependencies :
    /boost/config//boost_config
    /boost/container_hash//boost_container_hash
    /boost/core//boost_core
-    /boost/static_assert//boost_static_assert
    /boost/throw_exception//boost_throw_exception
    /boost/utility//boost_utility ;

--- a/doc/Jamfile
+++ b/doc/Jamfile
@@ -9,22 +9,21 @@

 project static_string/doc ;

-import boostbook ;
-import type ;
-import os ;
 import-search /boost/docca ;
-import docca ;

-docca.reference reference.qbk
+import docca ;
+import path ;
+import os ;
+
+local include-prefix = [ path.root $(__file__:D) [ path.pwd ] ] ;
+include-prefix = [ path.native $(include-prefix:D)/include ] ;
+
+docca.pyreference reference.qbk
    :
-        xsl/custom-overrides.xsl
        [ glob-tree-ex ../include/boost/static_string : *.hpp *.ipp : detail impl ]
+        externals.hpp
    :
-        <doxygen:param>PROJECT_NAME=StaticString
-        <doxygen:param>PROJECT_BRIEF="Static String Library"
        <doxygen:param>ALIASES="esafe=\"@par Exception Safety\""
-        <doxygen:param>FILE_PATTERNS=
-        <doxygen:param>EXAMPLE_PATTERNS=
        <doxygen:param>DISTRIBUTE_GROUP_DOC=YES
        <doxygen:param>MACRO_EXPANSION=YES
        <doxygen:param>EXPAND_ONLY_PREDEF=YES
@@ -41,19 +40,17 @@ docca.reference reference.qbk
        <doxygen:param>EXTRACT_ALL=YES
        <doxygen:param>EXTRACT_PRIVATE=YES
        <doxygen:param>EXTRACT_LOCAL_CLASSES=NO
-        <doxygen:param>SHOW_INCLUDE_FILES=NO
        <doxygen:param>INLINE_INFO=NO
        <doxygen:param>SORT_MEMBER_DOCS=NO
        <doxygen:param>SORT_MEMBERS_CTORS_1ST=YES
-        <doxygen:param>SHOW_USED_FILES=NO
-        <doxygen:param>SHOW_FILES=NO
-        <doxygen:param>SHOW_NAMESPACES=NO
-        <doxygen:param>CLASS_DIAGRAMS=NO
+        <doxygen:param>STRIP_FROM_PATH=$(include-prefix)

        # <doxygen:param>ALLOW_UNICODE_NAMES=NO
        # <doxygen:param>GROUP_NESTED_COMPOUNDS=NO
        # <doxygen:param>HIDE_COMPOUND_REFERENCE=NO
        # <doxygen:param>WARN_AS_ERROR=NO
+
+        <docca:config>config.json
    ;

 #-------------------------------------------------------------------------------
--- a/doc/config.json
+++ b/doc/config.json
@@ -0,0 +1,12 @@
+{
+    "include_private": false,
+    "legacy_behavior": false,
+    "external_marker": "!EXTERNAL!",
+    "link_prefix": "static_string.ref.",
+    "default_namespace": "boost::static_strings",
+    "allowed_prefixes": ["boost::static_strings::", "std::"],
+    "convenience_header": "boost/static_string.hpp",
+    "replace_strings": {
+        "__see_below__": "``['see-below]``"
+    }
+}
--- a/doc/externals.hpp
+++ b/doc/externals.hpp
@@ -0,0 +1,64 @@
+#pragma once
+
+namespace boost {
+
+/// !EXTERNAL!
+///
+/// @see https://www.boost.org/doc/libs/release/libs/utility/doc/html/utility/utilities/string_view.html
+template <class T, class Traits>
+struct basic_string_view {};
+
+} // namespace boost
+
+namespace std {
+
+/// !EXTERNAL!
+///
+/// @see https://en.cppreference.com/w/cpp/iterator/reverse_iterator
+template <class T>
+struct reverse_iterator {};
+
+/// !EXTERNAL!
+///
+/// @see https://en.cppreference.com/w/cpp/types/size_t
+struct size_t {};
+
+/// !EXTERNAL!
+///
+/// @see https://en.cppreference.com/w/cpp/types/integer
+struct uint64_t {};
+
+/// !EXTERNAL!
+///
+/// @see https://en.cppreference.com/w/cpp/types/integer
+struct int64_t {};
+
+/// !EXTERNAL!
+///
+/// @see https://en.cppreference.com/w/cpp/types/nullptr_t
+struct nullptr_t {};
+
+/// !EXTERNAL!
+///
+/// @see https://en.cppreference.com/w/cpp/types/ptrdiff_t
+struct ptrdiff_t {};
+
+/// !EXTERNAL!
+///
+/// @see https://en.cppreference.com/w/cpp/utility/initializer_list
+template <class T>
+struct initializer_list {};
+
+/// !EXTERNAL!
+///
+/// @see https://en.cppreference.com/w/cpp/io/basic_ostream
+template <class T, class Traits>
+struct basic_ostream {};
+
+/// !EXTERNAL!
+///
+/// @see https://en.cppreference.com/w/cpp/types/numeric_limits
+template <class T>
+struct numeric_limits {};
+
+} // namespace std
--- a/doc/xsl/custom-overrides.xsl
+++ b/doc/xsl/custom-overrides.xsl
@@ -1,11 +0,0 @@
-<xsl:stylesheet version="3.0"
-  xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
-  xmlns:xs="http://www.w3.org/2001/XMLSchema"
-  exclude-result-prefixes="xs"
-  expand-text="yes">
-
-  <xsl:variable name="doc-ref" select="'static_string.ref'"/>
-  <xsl:variable name="doc-ns" select="'boost::static_strings'"/>
-  <xsl:variable name="include-private-members" select="false()"/>
-
-</xsl:stylesheet>
--- a/example/static_cstring/Jamfile
+++ b/example/static_cstring/Jamfile
@@ -0,0 +1,19 @@
+#
+# Copyright (c) 2025 Gennaro Prota (gennaro dot prota at gmail dot com)
+#
+# Distributed under the Boost Software License, Version 1.0. (See accompanying
+# file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
+#
+# Official repository: https://github.com/boostorg/static_string
+#
+
+import testing ;
+
+project
+  : requirements
+    <include>../../include
+    <warnings>extra
+    <cxxstd>20
+  ;
+
+run static_cstring_test.cpp ;
--- a/example/static_cstring/README.md
+++ b/example/static_cstring/README.md
@@ -0,0 +1,13 @@
+This directory contains an experimental implementation of `basic_static_cstring`, which differs from `basic_static_string` in the following ways:
+
+|                     | `basic_static_cstring` | `basic_static_string` |
+|---------------------|------------------------|-----------------------|
+| Layout              | `sizeof == N + 1`      | Has size member       |
+| Embedded NULs       | Not supported          | Supported             |
+| Trivially copyable  | Yes                    | No                    |
+
+Additionally, when `N <= UCHAR_MAX`, `basic_static_cstring` employs an optimization that avoids calling `std::strlen()` to compute the size.
+
+This work stems from [boostorg/static_string#23](https://github.com/boostorg/static_string/issues/23).
+
+If you believe `basic_static_cstring` should become part of the public API, please share your feedback on the Boost mailing list.
--- a/example/static_cstring/static_cstring.hpp
+++ b/example/static_cstring/static_cstring.hpp
@@ -0,0 +1,441 @@
+//
+// Copyright (c) 2025 Gennaro Prota (gennaro dot prota at gmail dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
+//
+// Official repository: https://github.com/boostorg/static_string
+//
+
+#ifndef BOOST_STATIC_STRING_STATIC_CSTRING_HPP
+#define BOOST_STATIC_STRING_STATIC_CSTRING_HPP
+
+#include <boost/static_string/config.hpp>
+#include <algorithm>
+#include <climits>
+#include <cstddef>
+#include <ostream>
+#include <string>
+#include <string_view>
+#include <stdexcept>
+#include <type_traits>
+
+namespace boost {
+namespace static_strings {
+
+namespace detail {
+
+// Primary template: No remaining-capacity trick; uses traits::length() for length.
+template<std::size_t N, typename CharT, typename Traits, bool UseRemaining>
+class static_cstring_base
+{
+public:
+    using traits_type = Traits;
+    using value_type = CharT;
+    using size_type = std::size_t;
+
+    value_type data_[N + 1]{};
+
+    constexpr size_type get_size() const noexcept
+    {
+        return traits_type::length(data_);
+    }
+
+    constexpr void set_size(size_type sz) noexcept
+    {
+        data_[sz] = value_type{};
+    }
+
+    // Defaulted comparisons for structural type support.
+    constexpr bool operator==(const static_cstring_base&) const noexcept = default;
+    constexpr auto operator<=>(const static_cstring_base&) const noexcept = default;
+};
+
+// Specialization for N <= UCHAR_MAX: Uses remaining-capacity trick.
+template<std::size_t N, typename CharT, typename Traits>
+class static_cstring_base<N, CharT, Traits, true>
+{
+public:
+    using traits_type = Traits;
+    using value_type = CharT;
+    using size_type = std::size_t;
+
+    value_type data_[N + 1]{};
+
+    constexpr size_type get_size() const noexcept
+    {
+        return N - static_cast<unsigned char>(data_[N]);
+    }
+
+    constexpr void set_size(size_type sz) noexcept
+    {
+        data_[sz] = value_type{};
+        data_[N] = static_cast<value_type>(N - sz);
+    }
+
+    // Defaulted comparisons for structural type support.
+    constexpr bool operator==(const static_cstring_base&) const noexcept = default;
+    constexpr auto operator<=>(const static_cstring_base&) const noexcept = default;
+};
+
+} // namespace detail
+
+template<std::size_t N, typename CharT = char, typename Traits = std::char_traits<CharT>>
+class basic_static_cstring
+    : public detail::static_cstring_base<N, CharT, Traits, (N <= UCHAR_MAX)>
+{
+public:
+    using base = detail::static_cstring_base<N, CharT, Traits, (N <= UCHAR_MAX)>;
+    using base::data_;
+    using base::get_size;
+    using base::set_size;
+
+    // Member types
+    using traits_type     = Traits;
+    using value_type      = CharT;
+    using size_type       = std::size_t;
+    using difference_type = std::ptrdiff_t;
+    using reference       = value_type&;
+    using const_reference = const value_type&;
+    using pointer         = value_type*;
+    using const_pointer   = const value_type*;
+    using iterator        = pointer;
+    using const_iterator  = const_pointer;
+
+    static constexpr size_type npos = static_cast<size_type>(-1);
+    static constexpr size_type static_capacity = N;
+
+    // Constructors.
+    constexpr basic_static_cstring() noexcept
+    {
+        set_size(0);
+    }
+
+    constexpr basic_static_cstring(const CharT* s)
+    {
+        assign(s);
+    }
+
+    constexpr basic_static_cstring(const CharT* s, size_type count)
+    {
+        assign(s, count);
+    }
+
+    constexpr basic_static_cstring(size_type count, CharT ch)
+    {
+        assign(count, ch);
+    }
+
+    template<std::size_t M>
+    constexpr basic_static_cstring(const CharT (&arr)[M])
+    {
+        static_assert(M <= N + 1, "String literal too long for static_cstring");
+        assign(arr, M - 1);
+    }
+
+    constexpr size_type size() const noexcept
+    {
+        return get_size();
+    }
+
+    constexpr size_type length() const noexcept
+    {
+        return size();
+    }
+
+    constexpr bool empty() const noexcept
+    {
+        return data_[0] == value_type{};
+    }
+
+    static constexpr size_type max_size() noexcept
+    {
+        return N;
+    }
+
+    static constexpr size_type capacity() noexcept
+    {
+        return N;
+    }
+
+    // Element access.
+    constexpr reference operator[](size_type pos) noexcept
+    {
+        return data_[pos];
+    }
+
+    constexpr const_reference operator[](size_type pos) const noexcept
+    {
+        return data_[pos];
+    }
+
+    constexpr reference at(size_type pos)
+    {
+        if (pos >= size())
+        {
+            throw std::out_of_range("static_cstring::at");
+        }
+        return data_[pos];
+    }
+
+    constexpr const_reference at(size_type pos) const
+    {
+        if (pos >= size())
+        {
+            throw std::out_of_range("static_cstring::at");
+        }
+        return data_[pos];
+    }
+
+    constexpr reference front() noexcept
+    {
+        BOOST_STATIC_STRING_ASSERT(!empty());
+        return data_[0];
+    }
+
+    constexpr const_reference front() const noexcept
+    {
+        BOOST_STATIC_STRING_ASSERT(!empty());
+        return data_[0];
+    }
+
+    constexpr reference back() noexcept
+    {
+        BOOST_STATIC_STRING_ASSERT(!empty());
+        return data_[size() - 1];
+    }
+
+    constexpr const_reference back() const noexcept
+    {
+        BOOST_STATIC_STRING_ASSERT(!empty());
+        return data_[size() - 1];
+    }
+
+    constexpr pointer data() noexcept
+    {
+        return data_;
+    }
+
+    constexpr const_pointer data() const noexcept
+    {
+        return data_;
+    }
+
+    constexpr const_pointer c_str() const noexcept
+    {
+        return data_;
+    }
+
+    // Iterators.
+    constexpr iterator begin() noexcept
+    {
+        return data_;
+    }
+
+    constexpr const_iterator begin() const noexcept
+    {
+        return data_;
+    }
+
+    constexpr const_iterator cbegin() const noexcept
+    {
+        return data_;
+    }
+
+    constexpr iterator end() noexcept
+    {
+        return data_ + size();
+    }
+
+    constexpr const_iterator end() const noexcept
+    {
+        return data_ + size();
+    }
+
+    constexpr const_iterator cend() const noexcept
+    {
+        return data_ + size();
+    }
+
+    // Modifiers.
+    constexpr void clear() noexcept
+    {
+        set_size(0);
+    }
+
+    constexpr basic_static_cstring& assign(const CharT* s)
+    {
+        return assign(s, traits_type::length(s));
+    }
+
+    constexpr basic_static_cstring& assign(const CharT* s, size_type count)
+    {
+        if (count > N)
+        {
+            throw std::length_error("static_cstring::assign");
+        }
+        traits_type::copy(data_, s, count);
+        set_size(count);
+        return *this;
+    }
+
+    constexpr basic_static_cstring& assign(size_type count, CharT ch)
+    {
+        if (count > N)
+        {
+            throw std::length_error("static_cstring::assign");
+        }
+        traits_type::assign(data_, count, ch);
+        set_size(count);
+        return *this;
+    }
+
+    constexpr basic_static_cstring& operator=(const CharT* s)
+    {
+        return assign(s);
+    }
+
+    constexpr void push_back(CharT ch)
+    {
+        const size_type sz = size();
+        if (sz >= N)
+        {
+            throw std::length_error("static_cstring::push_back");
+        }
+        data_[sz] = ch;
+        set_size(sz + 1);
+    }
+
+    constexpr void pop_back() noexcept
+    {
+        BOOST_STATIC_STRING_ASSERT(!empty());
+        set_size(size() - 1);
+    }
+
+    constexpr basic_static_cstring& append(const CharT* s)
+    {
+        return append(s, traits_type::length(s));
+    }
+
+    constexpr basic_static_cstring& append(const CharT* s, size_type count)
+    {
+        const size_type sz = size();
+        if (sz + count > N)
+        {
+            throw std::length_error("static_cstring::append");
+        }
+        traits_type::copy(data_ + sz, s, count);
+        set_size(sz + count);
+        return *this;
+    }
+
+    constexpr basic_static_cstring& append(size_type count, CharT ch)
+    {
+        const size_type sz = size();
+        if (sz + count > N)
+        {
+            throw std::length_error("static_cstring::append");
+        }
+        traits_type::assign(data_ + sz, count, ch);
+        set_size(sz + count);
+        return *this;
+    }
+
+    constexpr basic_static_cstring& operator+=(const CharT* s)
+    {
+        return append(s);
+    }
+
+    constexpr basic_static_cstring& operator+=(CharT ch)
+    {
+        push_back(ch);
+        return *this;
+    }
+
+    // Comparisons.
+    constexpr int compare(const basic_static_cstring& other) const noexcept
+    {
+        const size_type lhs_sz = size();
+        const size_type rhs_sz = other.size();
+        const int result = traits_type::compare(data_, other.data_, (std::min)(lhs_sz, rhs_sz));
+
+        return result != 0
+                 ? result
+                 : lhs_sz < rhs_sz
+                 ? -1
+                 : lhs_sz > rhs_sz
+                 ? 1
+                 : 0;
+    }
+
+    constexpr int compare(const CharT* s) const noexcept
+    {
+        return compare(basic_static_cstring(s));
+    }
+
+    // Conversions.
+    constexpr operator std::basic_string_view<CharT, Traits>() const noexcept
+    {
+        return {data_, size()};
+    }
+
+    std::basic_string<CharT, Traits> str() const
+    {
+        return {data_, size()};
+    }
+
+    // Swap.
+    constexpr void swap(basic_static_cstring& other) noexcept
+    {
+        basic_static_cstring tmp = *this;
+        *this = other;
+        other = tmp;
+    }
+
+    // Defaulted comparisons for structural type (C++20).
+    constexpr bool operator==(const basic_static_cstring&) const noexcept = default;
+    constexpr auto operator<=>(const basic_static_cstring&) const noexcept = default;
+};
+
+#if defined(BOOST_STATIC_STRING_USE_DEDUCT)
+
+// Deduction guide.
+template<std::size_t N, typename CharT>
+basic_static_cstring(const CharT(&)[N]) -> basic_static_cstring<N - 1, CharT>;
+
+#endif
+
+// Comparison with const CharT*.
+template<std::size_t N, typename CharT, typename Traits>
+constexpr bool operator==(const basic_static_cstring<N, CharT, Traits>& lhs,
+                          const CharT* rhs) noexcept
+{
+    return lhs.compare(rhs) == 0;
+}
+
+template<std::size_t N, typename CharT, typename Traits>
+constexpr bool operator==(const CharT* lhs,
+                          const basic_static_cstring<N, CharT, Traits>& rhs) noexcept
+{
+    return rhs.compare(lhs) == 0;
+}
+
+// Stream output.
+template<std::size_t N, typename CharT, typename Traits>
+std::basic_ostream<CharT, Traits>& operator<<(std::basic_ostream<CharT, Traits>& os,
+                                              const basic_static_cstring<N, CharT, Traits>& str)
+{
+    return os << str.c_str();
+}
+
+// Alias templates.
+template<std::size_t N>
+using static_cstring = basic_static_cstring<N, char>;
+
+template<std::size_t N>
+using static_wcstring = basic_static_cstring<N, wchar_t>;
+
+}
+}
+
+#endif
--- a/example/static_cstring/static_cstring_test.cpp
+++ b/example/static_cstring/static_cstring_test.cpp
@@ -0,0 +1,671 @@
+//
+// Copyright (c) 2025 Gennaro Prota (gennaro dot prota at gmail dot com)
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
+//
+// Official repository: https://github.com/boostorg/static_string
+//
+
+#include "static_cstring.hpp"
+
+#include <boost/core/lightweight_test.hpp>
+#include <climits>
+#include <cstring>
+#include <sstream>
+#include <string>
+#include <string_view>
+#include <type_traits>
+
+namespace boost {
+namespace static_strings {
+
+static
+void
+testCStringSizeGuarantee()
+{
+    // Core guarantee: sizeof is exactly N + 1 (no size member).
+    static_assert(sizeof(static_cstring<0>) == 1, "");
+    static_assert(sizeof(static_cstring<1>) == 2, "");
+    static_assert(sizeof(static_cstring<10>) == 11, "");
+    static_assert(sizeof(static_cstring<63>) == 64, "");
+    static_assert(sizeof(static_cstring<64>) == 65, "");
+    static_assert(sizeof(static_cstring<127>) == 128, "");
+    static_assert(sizeof(static_cstring<UCHAR_MAX>) == (UCHAR_MAX + 1), "");
+    static_assert(sizeof(static_cstring<UCHAR_MAX + 1>) == (UCHAR_MAX + 2), "");
+    static_assert(sizeof(static_cstring<1000>) == 1001, "");
+}
+
+static
+void
+testCStringRemainingCapacityTrick()
+{
+    // Test the remaining-capacity optimization for N <= UCHAR_MAX.
+
+    // Full capacity: Last byte is both null terminator AND remaining == 0.
+    {
+        static_cstring<5> full("12345");
+        BOOST_TEST(full.size() == 5);
+        BOOST_TEST(full.capacity() == 5);
+        BOOST_TEST(full.data()[5] == '\0');
+        BOOST_TEST(std::strcmp(full.c_str(), "12345") == 0);
+    }
+
+    // Partial fill: Null terminator at position size, remaining at position N.
+    {
+        static_cstring<10> partial("Hi");
+        BOOST_TEST(partial.size() == 2);
+        BOOST_TEST(partial.capacity() == 10);
+        BOOST_TEST(partial.data()[2] == '\0');
+        BOOST_TEST(static_cast<unsigned char>(partial.data()[10]) == 8);
+    }
+
+    // Empty string.
+    {
+        static_cstring<10> empty;
+        BOOST_TEST(empty.size() == 0);
+        BOOST_TEST(empty.capacity() == 10);
+        BOOST_TEST(empty.data()[0] == '\0');
+        BOOST_TEST(static_cast<unsigned char>(empty.data()[10]) == 10);
+    }
+
+    // Edge case: N == UCHAR_MAX (max for our trick).
+    {
+        static_cstring<UCHAR_MAX> large;
+        large.assign(100, 'x');
+        BOOST_TEST(large.size() == 100);
+        BOOST_TEST(large.capacity() == UCHAR_MAX);
+        BOOST_TEST(static_cast<unsigned char>(large.data()[UCHAR_MAX]) == (UCHAR_MAX - large.size()));
+    }
+}
+
+template<typename S>
+struct CStringTypeTraits
+{
+    static_assert(std::is_trivially_copyable<S>::value);
+    static_assert(std::is_trivially_copy_constructible<S>::value);
+    static_assert(std::is_trivially_move_constructible<S>::value);
+    static_assert(std::is_trivially_copy_assignable<S>::value);
+    static_assert(std::is_trivially_move_assignable<S>::value);
+    static_assert(std::is_trivially_destructible<S>::value);
+};
+
+static
+void
+testCStringTypeTraits()
+{
+    {
+        using S = static_cstring<0>;
+        CStringTypeTraits< S > check;
+        static_cast<void>(check);
+    }
+    {
+        using S = static_cstring<63>;
+        CStringTypeTraits< S > check;
+        static_cast<void>(check);
+    }
+    {
+        using S = static_cstring<300>;
+        CStringTypeTraits< S > check;
+        static_cast<void>(check);
+    }
+}
+
+static
+void
+testCStringConstruct()
+{
+    // Default construction.
+    {
+        static_cstring<1> s;
+        BOOST_TEST(s.empty());
+        BOOST_TEST(s.size() == 0);
+        BOOST_TEST(s == "");
+        BOOST_TEST(*s.end() == 0);
+    }
+
+    // Construct with count and char.
+    {
+        static_cstring<4> s1(3, 'x');
+        BOOST_TEST(!s1.empty());
+        BOOST_TEST(s1.size() == 3);
+        BOOST_TEST(s1 == "xxx");
+        BOOST_TEST(*s1.end() == 0);
+        BOOST_TEST_THROWS(
+            (static_cstring<2>(3, 'x')),
+            std::length_error);
+    }
+
+    // Construct from a C string.
+    {
+        static_cstring<5> s1("12345");
+        BOOST_TEST(s1.size() == 5);
+        BOOST_TEST(s1 == "12345");
+        BOOST_TEST(*s1.end() == 0);
+        BOOST_TEST_THROWS(
+            (static_cstring<4>("12345")),
+            std::length_error);
+    }
+
+    // Construct from a C string with count.
+    {
+        static_cstring<5> s1("UVXYZ", 3);
+        BOOST_TEST(s1 == "UVX");
+        BOOST_TEST(*s1.end() == 0);
+    }
+
+    // Copy construction.
+    {
+        static_cstring<5> s1("12345");
+        static_cstring<5> s2(s1);
+        BOOST_TEST(s2 == "12345");
+        BOOST_TEST(*s2.end() == 0);
+    }
+}
+
+static
+void
+testCStringAssignment()
+{
+    // assign(size_type count, CharT ch).
+    BOOST_TEST(static_cstring<3>{}.assign(1, '*') == "*");
+    BOOST_TEST(static_cstring<3>{}.assign(3, '*') == "***");
+    BOOST_TEST(static_cstring<3>{"abc"}.assign(3, '*') == "***");
+    BOOST_TEST_THROWS(static_cstring<1>{"a"}.assign(2, '*'), std::length_error);
+
+    // assign(CharT const* s, size_type count).
+    BOOST_TEST(static_cstring<3>{}.assign("abc", 3) == "abc");
+    BOOST_TEST(static_cstring<3>{"*"}.assign("abc", 3) == "abc");
+    BOOST_TEST_THROWS(static_cstring<1>{}.assign("abc", 3), std::length_error);
+
+    // assign(CharT const* s).
+    BOOST_TEST(static_cstring<3>{}.assign("abc") == "abc");
+    BOOST_TEST(static_cstring<3>{"*"}.assign("abc") == "abc");
+    BOOST_TEST_THROWS(static_cstring<1>{}.assign("abc"), std::length_error);
+
+    // operator=(const CharT* s).
+    {
+        static_cstring<3> s1;
+        s1 = "123";
+        BOOST_TEST(s1 == "123");
+        BOOST_TEST(*s1.end() == 0);
+        static_cstring<1> s2;
+        BOOST_TEST_THROWS(
+            s2 = "123",
+            std::length_error);
+    }
+
+    // Copy assignment.
+    {
+        static_cstring<3> s1("123");
+        static_cstring<3> s2;
+        s2 = s1;
+        BOOST_TEST(s2 == "123");
+        BOOST_TEST(*s2.end() == 0);
+    }
+}
+
+static
+void
+testCStringElements()
+{
+    using ccs3 = static_cstring<3> const;
+
+    // at(size_type pos).
+    BOOST_TEST(static_cstring<3>{"abc"}.at(0) == 'a');
+    BOOST_TEST(static_cstring<3>{"abc"}.at(2) == 'c');
+    BOOST_TEST_THROWS(static_cstring<3>{""}.at(0), std::out_of_range);
+    BOOST_TEST_THROWS(static_cstring<3>{"abc"}.at(4), std::out_of_range);
+
+    // at(size_type pos) const.
+    BOOST_TEST(ccs3{"abc"}.at(0) == 'a');
+    BOOST_TEST(ccs3{"abc"}.at(2) == 'c');
+    BOOST_TEST_THROWS(ccs3{""}.at(0), std::out_of_range);
+
+    // operator[](size_type pos).
+    BOOST_TEST(static_cstring<3>{"abc"}[0] == 'a');
+    BOOST_TEST(static_cstring<3>{"abc"}[2] == 'c');
+    BOOST_TEST(static_cstring<3>{"abc"}[3] == 0);
+    BOOST_TEST(static_cstring<3>{""}[0] == 0);
+
+    // front() / back().
+    BOOST_TEST(static_cstring<3>{"abc"}.front() == 'a');
+    BOOST_TEST(static_cstring<3>{"abc"}.back() == 'c');
+
+    // data() / c_str().
+    {
+        static_cstring<3> s("123");
+        BOOST_TEST(std::memcmp(s.data(), "123", 3) == 0);
+        BOOST_TEST(std::memcmp(s.c_str(), "123\0", 4) == 0);
+    }
+
+    // Modification through element access.
+    {
+        static_cstring<5> s("12345");
+        s[1] = '_';
+        BOOST_TEST(s == "1_345");
+        s.front() = 'A';
+        BOOST_TEST(s == "A_345");
+        s.back() = 'Z';
+        BOOST_TEST(s == "A_34Z");
+    }
+}
+
+static
+void
+testCStringIterators()
+{
+    {
+        static_cstring<3> s;
+        BOOST_TEST(std::distance(s.begin(), s.end()) == 0);
+        s = "123";
+        BOOST_TEST(std::distance(s.begin(), s.end()) == 3);
+    }
+    {
+        static_cstring<3> const s("123");
+        BOOST_TEST(std::distance(s.begin(), s.end()) == 3);
+        BOOST_TEST(std::distance(s.cbegin(), s.cend()) == 3);
+    }
+
+    // Iteration.
+    {
+        static_cstring<5> s("hello");
+        std::string result;
+        for (const char c : s)
+        {
+            result += c;
+        }
+        BOOST_TEST(result == "hello");
+    }
+}
+
+static
+void
+testCStringCapacity()
+{
+    // empty().
+    BOOST_TEST(static_cstring<0>{}.empty());
+    BOOST_TEST(static_cstring<1>{}.empty());
+    BOOST_TEST(!static_cstring<1>{"a"}.empty());
+
+    // size().
+    BOOST_TEST(static_cstring<0>{}.size() == 0);
+    BOOST_TEST(static_cstring<1>{"a"}.size() == 1);
+    BOOST_TEST(static_cstring<5>{"abc"}.size() == 3);
+
+    // length().
+    BOOST_TEST(static_cstring<0>{}.length() == 0);
+    BOOST_TEST(static_cstring<3>{"abc"}.length() == 3);
+
+    // max_size().
+    BOOST_TEST(static_cstring<0>{}.max_size() == 0);
+    BOOST_TEST(static_cstring<5>{"abc"}.max_size() == 5);
+
+    // capacity().
+    BOOST_TEST(static_cstring<0>{}.capacity() == 0);
+    BOOST_TEST(static_cstring<5>{"abc"}.capacity() == 5);
+}
+
+static
+void
+testCStringClear()
+{
+    static_cstring<3> s("123");
+    BOOST_TEST(!s.empty());
+    s.clear();
+    BOOST_TEST(s.empty());
+    BOOST_TEST(s.size() == 0);
+    BOOST_TEST(*s.end() == 0);
+    BOOST_TEST(s == "");
+}
+
+static
+void
+testCStringPushPop()
+{
+    // push_back().
+    {
+        static_cstring<5> s("abc");
+        s.push_back('d');
+        BOOST_TEST(s == "abcd");
+        BOOST_TEST(s.size() == 4);
+        BOOST_TEST(*s.end() == 0);
+
+        s.push_back('e');
+        BOOST_TEST(s == "abcde");
+        BOOST_TEST(s.size() == 5);
+
+        BOOST_TEST_THROWS(s.push_back('f'), std::length_error);
+    }
+
+    // pop_back().
+    {
+        static_cstring<5> s("abcde");
+        s.pop_back();
+        BOOST_TEST(s == "abcd");
+        BOOST_TEST(s.size() == 4);
+        BOOST_TEST(*s.end() == 0);
+
+        s.pop_back();
+        s.pop_back();
+        s.pop_back();
+        s.pop_back();
+        BOOST_TEST(s.empty());
+    }
+}
+
+static
+void
+testCStringAppend()
+{
+    // append(const CharT* s).
+    {
+        static_cstring<12> s("Hello");
+        s.append(", World");
+        BOOST_TEST(s == "Hello, World");
+        BOOST_TEST(*s.end() == 0);
+    }
+    {
+        static_cstring<5> s("abc");
+        BOOST_TEST_THROWS(s.append("def"), std::length_error);
+    }
+
+    // append(const CharT* s, size_type count)
+    {
+        static_cstring<10> s("abc");
+        s.append("defgh", 3);
+        BOOST_TEST(s == "abcdef");
+        BOOST_TEST(*s.end() == 0);
+    }
+
+    // append(size_type count, CharT ch)
+    {
+        static_cstring<10> s("abc");
+        s.append(3, 'x');
+        BOOST_TEST(s == "abcxxx");
+        BOOST_TEST(*s.end() == 0);
+        BOOST_TEST_THROWS(s.append(5, 'y'), std::length_error);
+    }
+
+    // operator+=()
+    {
+        static_cstring<10> s("abc");
+        s += "def";
+        BOOST_TEST(s == "abcdef");
+        s += 'g';
+        BOOST_TEST(s == "abcdefg");
+        BOOST_TEST(*s.end() == 0);
+    }
+}
+
+static
+void
+testCStringComparison()
+{
+    // operator==() / operator!=().
+    {
+        static_cstring<10> a("abc");
+        static_cstring<10> b("abc");
+        static_cstring<10> c("abd");
+
+        BOOST_TEST(a == b);
+        BOOST_TEST(!(a == c));
+        BOOST_TEST(a != c);
+        BOOST_TEST(!(a != b));
+    }
+
+    // operator<(), <=(), >(), >=().
+    {
+        static_cstring<10> a("abc");
+        static_cstring<10> b("abd");
+
+        BOOST_TEST(a < b);
+        BOOST_TEST(a <= b);
+        BOOST_TEST(a <= a);
+        BOOST_TEST(b > a);
+        BOOST_TEST(b >= a);
+        BOOST_TEST(b >= b);
+    }
+
+    // Comparison with CharT const*.
+    {
+        static_cstring<10> s("hello");
+        BOOST_TEST(s == "hello");
+        BOOST_TEST("hello" == s);
+        BOOST_TEST(s != "world");
+        BOOST_TEST("world" != s);
+    }
+
+    // compare().
+    {
+        static_cstring<10> s("abc");
+        BOOST_TEST(s.compare("abc") == 0);
+        BOOST_TEST(s.compare("abd") < 0);
+        BOOST_TEST(s.compare("abb") > 0);
+    }
+}
+
+static
+void
+testCStringConversion()
+{
+    // operator string_view().
+    {
+        static_cstring<10> s("hello");
+        std::string_view sv = s;
+        BOOST_TEST(sv == "hello");
+        BOOST_TEST(sv.size() == 5);
+    }
+
+    // str().
+    {
+        static_cstring<10> s("hello");
+        std::string str = s.str();
+        BOOST_TEST(str == "hello");
+        BOOST_TEST(str.size() == 5);
+    }
+}
+
+static
+void
+testCStringStream()
+{
+    static_cstring<10> s("hello");
+    std::ostringstream oss;
+    oss << s;
+    BOOST_TEST(oss.str() == "hello");
+}
+
+static
+void
+testCStringSwap()
+{
+    static_cstring<10> a("hello");
+    static_cstring<10> b("world");
+
+    a.swap(b);
+
+    BOOST_TEST(a == "world");
+    BOOST_TEST(b == "hello");
+}
+
+static
+void
+testCStringConstexpr()
+{
+    // constexpr construction and operations.
+    constexpr static_cstring<10> ce("test");
+    static_assert(ce.size() == 4, "");
+    static_assert(ce[0] == 't', "");
+    static_assert(ce[1] == 'e', "");
+    static_assert(ce[2] == 's', "");
+    static_assert(ce[3] == 't', "");
+    static_assert(!ce.empty(), "");
+    static_assert(ce.max_size() == 10, "");
+    static_assert(ce.capacity() == 10, "");
+
+    constexpr static_cstring<5> ce_empty;
+    static_assert(ce_empty.empty(), "");
+    static_assert(ce_empty.size() == 0, "");
+}
+
+// Helper struct to test NTTP.
+template<basic_static_cstring S>
+struct NTTPHelper
+{
+    static constexpr std::size_t size() noexcept
+    {
+        return S.size();
+    }
+
+    static constexpr const char* c_str() noexcept
+    {
+        return S.c_str();
+    }
+};
+
+static
+void
+testCStringNTTP()
+{
+    // Test non-type template parameter usage (C++20).
+
+    // Test size deduction from string literals.
+    BOOST_TEST(NTTPHelper<"hello">::size() == 5);
+    BOOST_TEST(NTTPHelper<"">::size() == 0);
+    BOOST_TEST(NTTPHelper<"test">::size() == 4);
+
+    // Test that different strings create different types
+    constexpr bool same_type = std::is_same_v<
+        NTTPHelper<"hello">,
+        NTTPHelper<"hello">>;
+    BOOST_TEST(same_type);
+
+    constexpr bool different_type = !std::is_same_v<
+        NTTPHelper<"hello">,
+        NTTPHelper<"world">>;
+    BOOST_TEST(different_type);
+
+    // Test constexpr access.
+    constexpr std::size_t len = NTTPHelper<"constexpr">::size();
+    static_assert(len == 9, "");
+}
+
+static
+void
+testCStringPODUsage()
+{
+    // Test usage in POD types (the original motivation).
+    struct UserRecord
+    {
+        int id;
+        static_cstring<63> name;
+        unsigned int flags;
+    };
+
+    static_assert(sizeof(static_cstring<63>) == 64, "");
+    static_assert(std::is_trivially_copyable<UserRecord>::value, "");
+
+    UserRecord user{};
+    user.id = 42;
+    user.name = "Alice";
+    user.flags = 0xFF;
+
+    BOOST_TEST(user.id == 42);
+    BOOST_TEST(user.name.size() == 5);
+    BOOST_TEST(user.name == "Alice");
+    BOOST_TEST(user.flags == 0xFF);
+
+    // Copy the struct.
+    UserRecord copy = user;
+    BOOST_TEST(copy.name == "Alice");
+
+    // memcpy() should work.
+    UserRecord memcpy_dest;
+    std::memcpy(&memcpy_dest, &user, sizeof(UserRecord));
+    BOOST_TEST(memcpy_dest.name == "Alice");
+}
+
+static
+void
+testCStringLargeCapacity()
+{
+    // Test strings with N > UCHAR_MAX (no remaining-capacity trick).
+    {
+        static_cstring<300> s;
+        BOOST_TEST(s.empty());
+        BOOST_TEST(s.size() == 0);
+
+        s = "This is a test string";
+        BOOST_TEST(s.size() == 21);
+        BOOST_TEST(s == "This is a test string");
+
+        s.clear();
+        BOOST_TEST(s.empty());
+    }
+
+    // Large string operations.
+    {
+        static_cstring<500> s;
+        s.assign(400, 'x');
+        BOOST_TEST(s.size() == 400);
+        BOOST_TEST(s[0] == 'x');
+        BOOST_TEST(s[399] == 'x');
+        BOOST_TEST(*s.end() == 0);
+    }
+}
+
+static
+void
+testCStringWideChar()
+{
+    // Test with wchar_t.
+    {
+        static_wcstring<10> ws;
+        BOOST_TEST(ws.empty());
+        BOOST_TEST(ws.size() == 0);
+    }
+
+    {
+        static_wcstring<10> ws(L"hello");
+        BOOST_TEST(ws.size() == 5);
+        BOOST_TEST(ws[0] == L'h');
+        BOOST_TEST(ws[4] == L'o');
+        BOOST_TEST(*ws.end() == 0);
+    }
+}
+
+int
+runTests()
+{
+  testCStringSizeGuarantee();
+  testCStringRemainingCapacityTrick();
+  testCStringTypeTraits();
+  testCStringConstruct();
+  testCStringAssignment();
+  testCStringElements();
+  testCStringIterators();
+  testCStringCapacity();
+  testCStringClear();
+  testCStringPushPop();
+  testCStringAppend();
+  testCStringComparison();
+  testCStringConversion();
+  testCStringStream();
+  testCStringSwap();
+  testCStringConstexpr();
+  testCStringNTTP();
+  testCStringPODUsage();
+  testCStringLargeCapacity();
+  testCStringWideChar();
+
+  return report_errors();
+}
+}
+}
+
+int
+main()
+{
+  return boost::static_strings::runTests();
+}
--- a/include/boost/static_string/config.hpp
+++ b/include/boost/static_string/config.hpp
@@ -139,9 +139,6 @@
 #ifndef BOOST_STATIC_STRING_THROW
 #define BOOST_STATIC_STRING_THROW(ex) BOOST_THROW_EXCEPTION(ex)
 #endif
-#ifndef BOOST_STATIC_STRING_STATIC_ASSERT
-#define BOOST_STATIC_STRING_STATIC_ASSERT(cond, msg) BOOST_STATIC_ASSERT_MSG(cond, msg)
-#endif
 #ifndef BOOST_STATIC_STRING_ASSERT
 #define BOOST_STATIC_STRING_ASSERT(cond) BOOST_ASSERT(cond)
 #endif
@@ -149,9 +146,6 @@
 #ifndef BOOST_STATIC_STRING_THROW
 #define BOOST_STATIC_STRING_THROW(ex) throw ex
 #endif
-#ifndef BOOST_STATIC_STRING_STATIC_ASSERT
-#define BOOST_STATIC_STRING_STATIC_ASSERT(cond, msg) static_assert(cond, msg)
-#endif
 #ifndef BOOST_STATIC_STRING_ASSERT
 #define BOOST_STATIC_STRING_ASSERT(cond) assert(cond)
 #endif
@@ -161,7 +155,6 @@
 #include <boost/config.hpp>
 #include <boost/assert.hpp>
 #include <boost/container_hash/hash.hpp>
-#include <boost/static_assert.hpp>
 #include <boost/utility/string_view.hpp>
 #include <boost/core/detail/string_view.hpp>
 #include <boost/throw_exception.hpp>
@@ -175,27 +168,31 @@
 #include <cassert>
 #include <stdexcept>

+#if defined(__has_include)
+#  if !__has_include(<string_view>)
+#    define BOOST_STATIC_STRING_NO_CXX17_HDR_STRING_VIEW
+#  endif
 /*
 * Replicate the logic from Boost.Config
 */
 // GNU libstdc++3:
-#if defined(__GLIBCPP__) || defined(__GLIBCXX__)
-#if (BOOST_LIBSTDCXX_VERSION < 70100) || (__cplusplus <= 201402L)
-#  define BOOST_STATIC_STRING_NO_CXX17_HDR_STRING_VIEW
-#endif
+#elif defined(__GLIBCPP__) || defined(__GLIBCXX__)
+#  if ((__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__) < 70100) || (__cplusplus <= 201402L)
+#    define BOOST_STATIC_STRING_NO_CXX17_HDR_STRING_VIEW
+#  endif
 // libc++:
 #elif defined(_LIBCPP_VERSION)
-#if (_LIBCPP_VERSION < 4000) || (__cplusplus <= 201402L)
-#  define BOOST_STATIC_STRING_NO_CXX17_HDR_STRING_VIEW
-#endif
+#  if (_LIBCPP_VERSION < 4000) || (__cplusplus <= 201402L)
+#    define BOOST_STATIC_STRING_NO_CXX17_HDR_STRING_VIEW
+#  endif
 // MSVC uses logic from catch all for BOOST_NO_CXX17_HDR_STRING_VIEW
 // catch all:
 #elif !defined(_YVALS) && !defined(_CPPLIB_VER)
-#if (!defined(__has_include) || (__cplusplus < 201700))
-#  define BOOST_STATIC_STRING_NO_CXX17_HDR_STRING_VIEW
-#elif !__has_include(<string_view>)
-#  define BOOST_STATIC_STRING_NO_CXX17_HDR_STRING_VIEW
-#endif
+#  if (!defined(__has_include) || (__cplusplus < 201700))
+#    define BOOST_STATIC_STRING_NO_CXX17_HDR_STRING_VIEW
+#  elif !__has_include(<string_view>)
+#    define BOOST_STATIC_STRING_NO_CXX17_HDR_STRING_VIEW
+#  endif
 #endif

 #if !defined(BOOST_STATIC_STRING_NO_CXX17_HDR_STRING_VIEW) || \
@@ -278,4 +275,25 @@ using basic_string_view =
 } // boost
 #endif

-#endif
+#if defined(__cpp_lib_to_string) && __cpp_lib_to_string >= 202306L // std::to_[w]string() redefined in terms of std::format()
+#define BOOST_STATIC_STRING_USE_STD_FORMAT
+#endif
+
+#if defined(__GNUC__) && (__GNUC__ >= 5) && (__GNUC__ <= 10) && !defined(__clang__)
+// Workaround for GCC complaining about nested classes being private.
+#define BOOST_STATIC_STRING_GCC_NESTED_CLASS_WORKAROUND public:
+#else
+#define BOOST_STATIC_STRING_GCC_NESTED_CLASS_WORKAROUND
+#endif
+
+// GCC 9 incorrectly rejects the pointer equality comparison in
+// ptr_in_range() in constant expressions. GCC 10 and later handle
+// it correctly.
+//
+// Clang 3.7 and 9-19 have the same issue.
+#if (defined(__GNUC__) && !defined(__clang__) && (__GNUC__ == 9)) \
+    || (defined(__clang__) && ((__clang_major__ == 3 && __clang_minor__ == 7) || ((__clang_major__ >= 9) && (__clang_major__ <= 19))))
+#define BOOST_STATIC_STRING_CONSTEXPR_PTR_CMP_BROKEN
+#endif
+
+#endif
--- a/include/boost/static_string/static_string.hpp
+++ b/include/boost/static_string/static_string.hpp
@@ -34,6 +34,9 @@
 #include <algorithm>
 #include <cstdint>
 #include <cstdio>
+#if defined(BOOST_STATIC_STRING_USE_STD_FORMAT)
+#include <format>
+#endif
 #include <functional>
 #include <initializer_list>
 #include <limits>
@@ -311,103 +314,129 @@ copy_with_traits(
 template<std::size_t N, typename CharT, typename Traits>
 class static_string_base
 {
-private:
+  using derived_type = basic_static_string<N, CharT, Traits>;
+  friend derived_type;
+
  using size_type = smallest_width<N>;
  using value_type = typename Traits::char_type;
  using pointer = value_type*;
  using const_pointer = const value_type*;
-public:
-  BOOST_STATIC_STRING_CPP11_CONSTEXPR
-  static_string_base() noexcept { };

-  BOOST_STATIC_STRING_CPP14_CONSTEXPR
-  pointer
-  data_impl() noexcept
+BOOST_STATIC_STRING_GCC_NESTED_CLASS_WORKAROUND
+
+  struct size
  {
-    return data_;
-  }
+    class basic_static_string
+    {
+      friend derived_type;

-  BOOST_STATIC_STRING_CPP14_CONSTEXPR
-  const_pointer
-  data_impl() const noexcept
+      BOOST_STATIC_STRING_CPP11_CONSTEXPR
+      size_type
+      size_impl() const noexcept
+      {
+        return size;
+      }
+
+      BOOST_STATIC_STRING_CPP14_CONSTEXPR
+      size_type
+      size_impl(std::size_t n) noexcept
+      {
+        // Functions that set size will throw
+        // if the new size would exceed max_size()
+        // therefore we can guarantee that this will
+        // not lose data.
+        return size = static_cast<size_type>(n);
+      }
+
+    public:
+      size_type size = 0;
+    };
+  };
+
+  struct data
  {
-    return data_;
-  }
+    class basic_static_string
+    {
+      friend derived_type;

-  BOOST_STATIC_STRING_CPP11_CONSTEXPR
-  std::size_t
-  size_impl() const noexcept
-  {
-    return size_;
-  }
+      BOOST_STATIC_STRING_CPP14_CONSTEXPR
+      pointer
+      data_impl() noexcept
+      {
+        return data;
+      }

-  BOOST_STATIC_STRING_CPP14_CONSTEXPR
-  std::size_t
-  set_size(std::size_t n) noexcept
-  {
-    // Functions that set size will throw
-    // if the new size would exceed max_size()
-    // therefore we can guarantee that this will
-    // not lose data.
-    return size_ = size_type(n);
-  }
+      BOOST_STATIC_STRING_CPP11_CONSTEXPR
+      const_pointer
+      data_impl() const noexcept
+      {
+        return data;
+      }

-  BOOST_STATIC_STRING_CPP14_CONSTEXPR
-  void
-  term_impl() noexcept
-  {
-    Traits::assign(data_[size_], value_type());
-  }
-
-  size_type size_ = 0;
-
-  value_type data_[N + 1]{};
+    public:
+      value_type data[N + 1]{};
+    };
+  };
 };

 // Optimization for when the size is 0
 template<typename CharT, typename Traits>
 class static_string_base<0, CharT, Traits>
 {
-private:
+  using derived_type = basic_static_string<0, CharT, Traits>;
+  friend derived_type;
+
+  using size_type = std::size_t;
  using value_type = typename Traits::char_type;
  using pointer = value_type*;
-public:
-  BOOST_STATIC_STRING_CPP11_CONSTEXPR
-  static_string_base() noexcept { }

-  // Modifying the null terminator is UB
-  BOOST_STATIC_STRING_CPP11_CONSTEXPR
-  pointer
-  data_impl() const noexcept
+BOOST_STATIC_STRING_GCC_NESTED_CLASS_WORKAROUND
+
+  struct size
  {
-    return const_cast<pointer>(&null_);
-  }
+    class basic_static_string
+    {
+      friend derived_type;

-  BOOST_STATIC_STRING_CPP11_CONSTEXPR
-  std::size_t
-  size_impl() const noexcept
+      BOOST_STATIC_STRING_CPP11_CONSTEXPR
+      size_type
+      size_impl() const noexcept
+      {
+        return 0;
+      }
+
+      BOOST_STATIC_STRING_CPP11_CONSTEXPR
+      size_type
+      size_impl(std::size_t) const noexcept
+      {
+        return 0;
+      }
+    };
+  };
+
+  struct data
  {
-    return 0;
-  }
+    class basic_static_string
+    {
+      friend derived_type;

-  BOOST_STATIC_STRING_CPP11_CONSTEXPR
-  std::size_t
-  set_size(std::size_t) const noexcept
-  {
-    return 0;
-  }
+      BOOST_STATIC_STRING_CPP11_CONSTEXPR
+      pointer
+      data_impl() const noexcept
+      {
+        return const_cast<pointer>(&data);
+      }

-  BOOST_STATIC_STRING_CPP14_CONSTEXPR
-  void
-  term_impl() const noexcept { }
-
-private:
-  static constexpr const value_type null_{};
+    public:
+      static constexpr value_type data{};
+    };
+  };
 };

 // This is only needed in C++14 and lower.
 // see http://eel.is/c++draft/depr.static.constexpr
 #ifndef BOOST_STATIC_STRING_CPP17
+#if 0
 template<typename CharT, typename Traits>
 constexpr
 const
@@ -416,6 +445,13 @@ static_string_base<0, CharT, Traits>::
 null_;
 #endif

+template<typename CharT, typename Traits>
+constexpr
+typename static_string_base<0, CharT, Traits>::value_type
+static_string_base<0, CharT, Traits>::data::basic_static_string::data;
+#endif
+
+
 template<typename CharT, typename Traits>
 BOOST_STATIC_STRING_CPP14_CONSTEXPR
 inline
@@ -608,17 +644,42 @@ count_digits(std::size_t value)
 #pragma GCC diagnostic ignored "-Wformat-truncation"
 #endif

+#if defined(BOOST_STATIC_STRING_USE_STD_FORMAT)
+
+template<std::size_t N, typename FloatingPoint>
+inline
+static_string<N>
+cpp26_to_static_string(FloatingPoint value) noexcept
+{
+  using size_type = typename static_string<N>::size_type;
+  static_string<N> result;
+  result.resize_and_overwrite(
+    N,
+    [&](char* buffer, size_type) -> size_type
+    {
+      const auto formatted = std::format_to_n(buffer, N, "{}", value);
+      return formatted.size;
+    }
+  );
+  return result;
+}
+
+#endif
+
 template<std::size_t N>
 inline
 static_string<N>
 to_static_string_float_impl(double value) noexcept
 {
+#if defined(BOOST_STATIC_STRING_USE_STD_FORMAT)
+  return cpp26_to_static_string<N>(value);
+#else
  using size_type = typename static_string<N>::size_type;
+  static_string<N> result;
  // we have to assume here that no reasonable implementation
  // will require more than 2^63 chars to represent a float value.
  const long long narrow =
    static_cast<long long>(N);
-  static_string<N> result;
  result.resize_and_overwrite(
    N,
    [&](char* buffer, size_type) -> size_type
@@ -642,6 +703,19 @@ to_static_string_float_impl(double value) noexcept
    }
  );
  return result;
+#endif
+}
+
+template<std::size_t N>
+inline
+static_string<N>
+to_static_string_float_impl(float value) noexcept
+{
+#if defined(BOOST_STATIC_STRING_USE_STD_FORMAT)
+  return cpp26_to_static_string<N>(value);
+#else
+  return to_static_string_float_impl<N>(static_cast<double>(value));
+#endif
 }

 template<std::size_t N>
@@ -649,12 +723,15 @@ inline
 static_string<N>
 to_static_string_float_impl(long double value) noexcept
 {
+#if defined(BOOST_STATIC_STRING_USE_STD_FORMAT)
+  return cpp26_to_static_string<N>(value);
+#else
  using size_type = typename static_string<N>::size_type;
+  static_string<N> result;
  // we have to assume here that no reasonable implementation
  // will require more than 2^63 chars to represent a float value.
  const long long narrow =
    static_cast<long long>(N);
-  static_string<N> result;
  result.resize_and_overwrite(
    N,
    [&](char* buffer, size_type)->size_type
@@ -680,20 +757,46 @@ to_static_string_float_impl(long double value) noexcept
    }
  );
  return result;
+#endif
 }

 #ifdef BOOST_STATIC_STRING_HAS_WCHAR
+
+#if defined(BOOST_STATIC_STRING_USE_STD_FORMAT)
+template<std::size_t N, typename FloatingPoint>
+inline
+static_wstring<N>
+cpp26_to_static_wstring(FloatingPoint value) noexcept
+{
+  using size_type = typename static_wstring<N>::size_type;
+  static_wstring<N> result;
+  result.resize_and_overwrite(
+    N,
+    [&](wchar_t* buffer, size_type) -> size_type
+    {
+      const auto formatted = std::format_to_n(buffer, N, L"{}", value);
+      return formatted.size;
+    }
+  );
+  return result;
+}
+
+#endif
+
 template<std::size_t N>
 inline
 static_wstring<N>
 to_static_wstring_float_impl(double value) noexcept
 {
+#if defined(BOOST_STATIC_STRING_USE_STD_FORMAT)
+  return cpp26_to_static_wstring<N>(value);
+#else
  using size_type = typename static_wstring<N>::size_type;
+  static_wstring<N> result;
  // we have to assume here that no reasonable implementation
  // will require more than 2^63 chars to represent a float value.
  const long long narrow =
    static_cast<long long>(N);
-  static_wstring<N> result;
  result.resize_and_overwrite(
    N,
    [&](wchar_t* buffer, size_type) -> size_type
@@ -705,7 +808,7 @@ to_static_wstring_float_impl(double value) noexcept
      // circuit evaluation will ensure that the
      // second operand is not evaluated on conforming
      // implementations.
-      long long num_written =
+      int num_written =
          std::swprintf(buffer, N + 1, L"%f", value);
      if (num_written < 0 ||
          num_written > narrow)
@@ -724,6 +827,19 @@ to_static_wstring_float_impl(double value) noexcept
    }
  );
  return result;
+#endif
+}
+
+template<std::size_t N>
+inline
+static_wstring<N>
+to_static_wstring_float_impl(float value) noexcept
+{
+#if defined(BOOST_STATIC_STRING_USE_STD_FORMAT)
+  return cpp26_to_static_wstring<N>(value);
+#else
+    return to_static_wstring_float_impl<N>(static_cast<double>(value));
+#endif
 }

 template<std::size_t N>
@@ -731,12 +847,15 @@ inline
 static_wstring<N>
 to_static_wstring_float_impl(long double value) noexcept
 {
+#if defined(BOOST_STATIC_STRING_USE_STD_FORMAT)
+  return cpp26_to_static_wstring<N>(value);
+#else
  using size_type = typename static_wstring<N>::size_type;
+  static_wstring<N> result;
  // we have to assume here that no reasonable implementation
  // will require more than 2^63 chars to represent a float value.
  const long long narrow =
    static_cast<long long>(N);
-  static_wstring<N> result;
  result.resize_and_overwrite(
    N,
    [&](wchar_t* buffer, size_type) -> size_type
@@ -748,7 +867,7 @@ to_static_wstring_float_impl(long double value) noexcept
      // circuit evaluation will ensure that the
      // second operand is not evaluated on conforming
      // implementations.
-      long long num_written =
+      int num_written =
          std::swprintf(buffer, N + 1, L"%Lf", value);
      if (num_written < 0 ||
          num_written > narrow)
@@ -767,6 +886,7 @@ to_static_wstring_float_impl(long double value) noexcept
    }
  );
  return result;
+#endif
 }
 #endif

@@ -961,13 +1081,17 @@ throw_exception(const char* msg)
      basic_static_string<N, char8_t, std::char_traits<char8_t>>;
    @endcode

-    @see to_static_string
+    @see @ref to_static_string.
 */
 template<std::size_t N, typename CharT,
  typename Traits = std::char_traits<CharT>>
 class basic_static_string
 #ifndef BOOST_STATIC_STRING_DOCS
-  : private detail::static_string_base<N, CharT, Traits>
+  // : public detail::static_string_base<N, CharT, Traits>
+  : public detail::static_string_base<
+    N, CharT, Traits>::size::basic_static_string
+  , public detail::static_string_base<
+    N, CharT, Traits>::data::basic_static_string
 #endif
 {
 private:
@@ -1115,7 +1239,7 @@ public:
  BOOST_STATIC_STRING_CPP14_CONSTEXPR
  basic_static_string(const_pointer s)
  {
-    assign(s);
+    assign(s, s + traits_type::length(s));
  }

  /** Constructor.
@@ -1286,7 +1410,7 @@ public:
  basic_static_string&
  operator=(const_pointer s)
  {
-    return assign(s);
+    return assign(s, s + traits_type::length(s));
  }

  /** Assign to the string.
@@ -2252,7 +2376,7 @@ public:
  void
  clear() noexcept
  {
-    this->set_size(0);
+    this->size_impl(0);
    term();
  }

@@ -2844,7 +2968,7 @@ public:
  pop_back() noexcept
  {
    BOOST_STATIC_STRING_ASSERT(!empty());
-    this->set_size(size() - 1);
+    this->size_impl(size() - 1);
    term();
  }

@@ -3020,7 +3144,7 @@ public:
    InputIterator first,
    InputIterator last)
  {
-    this->set_size(size() + read_back(true, first, last));
+    this->size_impl(size() + read_back(true, first, last));
    return term();
  }

@@ -3646,8 +3770,8 @@ public:
      `{data() + pos, std::min(count, size() - pos))`.

      @param pos The index to being the substring at. The
-      default arugment for this parameter is `0`.
-      @param count The length of the substring. The default arugment
+      default argument for this parameter is `0`.
+      @param count The length of the substring. The default argument
      for this parameter is @ref npos.

      @throw std::out_of_range `pos > size()`
@@ -3677,8 +3801,8 @@ public:
      to `{data() + pos, std::min(count, size() - pos))`.

      @param pos The index to being the substring at. The
-      default arugment for this parameter is `0`.
-      @param count The length of the substring. The default arugment
+      default argument for this parameter is `0`.
+      @param count The length of the substring. The default argument
      for this parameter is @ref npos.

      @throw std::out_of_range `pos > size()`
@@ -5497,11 +5621,22 @@ public:
  }

 private:
+  BOOST_STATIC_STRING_CPP14_CONSTEXPR
+  void term_impl(std::true_type) noexcept
+  {
+    traits_type::assign(data()[size()], value_type());
+  }
+
+  BOOST_STATIC_STRING_CPP14_CONSTEXPR
+  void term_impl(std::false_type) noexcept
+  {
+  }
+
  BOOST_STATIC_STRING_CPP14_CONSTEXPR
  basic_static_string&
  term() noexcept
  {
-    this->term_impl();
+    term_impl(std::integral_constant<bool, N != 0>());
    return *this;
  }

@@ -5509,7 +5644,7 @@ private:
  basic_static_string&
  assign_char(value_type ch, std::true_type) noexcept
  {
-    this->set_size(1);
+    this->size_impl(1);
    traits_type::assign(data()[0], ch);
    return term();
  }
@@ -5583,7 +5718,7 @@ private:
    const_pointer s,
    size_type count) noexcept
  {
-    this->set_size(count);
+    this->size_impl(count);
    traits_type::copy(data(), s, size() + 1);
    return *this;
  }
@@ -6213,9 +6348,13 @@ operator<<(

 // Unsigned overloads have a + 1, for the missing digit.

-// Floating point overloads have a + 4, for the sign
-// of the integral part, sign of the exponent, the 'e',
-// and the decimal.
+// Floating point overloads have a +8 (for float), + 8
+// (for double), and +10 for long double (that accounts
+// for the sign of the integral part, the missing digit,
+// the decimal point, the sign of the exponent, the 'e'
+// and up to two, three or five digits of exponent---float
+// uses the same value as double, because we sometimes
+// reuse the conversion from double for floats).

 /// Converts `value` to a `static_string`
 static_string<std::numeric_limits<int>::digits10 + 2>
@@ -6272,30 +6411,30 @@ to_static_string(unsigned long long value) noexcept
 }

 /// Converts `value` to a `static_string`
-static_string<std::numeric_limits<float>::max_digits10 + 4>
+static_string<std::numeric_limits<float>::max_digits10 + 8>
 inline
 to_static_string(float value) noexcept
 {
  return detail::to_static_string_float_impl<
-    std::numeric_limits<float>::max_digits10 + 4>(value);
+    std::numeric_limits<float>::max_digits10 + 8>(value);
 }

 /// Converts `value` to a `static_string`
-static_string<std::numeric_limits<double>::max_digits10 + 4>
+static_string<std::numeric_limits<double>::max_digits10 + 8>
 inline
 to_static_string(double value) noexcept
 {
  return detail::to_static_string_float_impl<
-    std::numeric_limits<double>::max_digits10 + 4>(value);
+    std::numeric_limits<double>::max_digits10 + 8>(value);
 }

 /// Converts `value` to a `static_string`
-static_string<std::numeric_limits<long double>::max_digits10 + 4>
+static_string<std::numeric_limits<long double>::max_digits10 + 10>
 inline
 to_static_string(long double value) noexcept
 {
  return detail::to_static_string_float_impl<
-    std::numeric_limits<long double>::max_digits10 + 4>(value);
+    std::numeric_limits<long double>::max_digits10 + 10>(value);
 }

 #ifdef BOOST_STATIC_STRING_HAS_WCHAR
@@ -6354,30 +6493,30 @@ to_static_wstring(unsigned long long value) noexcept
 }

 /// Converts `value` to a `static_wstring`
-static_wstring<std::numeric_limits<float>::max_digits10 + 4>
+static_wstring<std::numeric_limits<float>::max_digits10 + 8>
 inline
 to_static_wstring(float value) noexcept
 {
  return detail::to_static_wstring_float_impl<
-    std::numeric_limits<float>::max_digits10 + 4>(value);
+    std::numeric_limits<float>::max_digits10 + 8>(value);
 }

 /// Converts `value` to a `static_wstring`
-static_wstring<std::numeric_limits<double>::max_digits10 + 4>
+static_wstring<std::numeric_limits<double>::max_digits10 + 8>
 inline
 to_static_wstring(double value) noexcept
 {
  return detail::to_static_wstring_float_impl<
-    std::numeric_limits<double>::max_digits10 + 4>(value);
+    std::numeric_limits<double>::max_digits10 + 8>(value);
 }

 /// Converts `value` to a `static_wstring`
-static_wstring<std::numeric_limits<long double>::max_digits10 + 4>
+static_wstring<std::numeric_limits<long double>::max_digits10 + 10>
 inline
 to_static_wstring(long double value) noexcept
 {
  return detail::to_static_wstring_float_impl<
-    std::numeric_limits<long double>::max_digits10 + 4>(value);
+    std::numeric_limits<long double>::max_digits10 + 10>(value);
 }
 #endif

@@ -6390,7 +6529,7 @@ to_static_wstring(long double value) noexcept
 #ifdef BOOST_STATIC_STRING_USE_DEDUCT
 template<std::size_t N, typename CharT>
 basic_static_string(const CharT(&)[N]) ->
-  basic_static_string<N, CharT, std::char_traits<CharT>>;
+  basic_static_string<N - 1, CharT, std::char_traits<CharT>>;
 #endif

 //------------------------------------------------------------------------------
@@ -6500,7 +6639,7 @@ assign(
  if (count > max_size())
    detail::throw_exception<std::length_error>(
      "count > max_size()");
-  this->set_size(count);
+  this->size_impl(count);
  traits_type::assign(data(), size(), ch);
  return term();
 }
@@ -6517,7 +6656,7 @@ assign(
  if (count > max_size())
    detail::throw_exception<std::length_error>(
      "count > max_size()");
-  this->set_size(count);
+  this->size_impl(count);
  traits_type::move(data(), s, size());
  return term();
 }
@@ -6539,13 +6678,13 @@ assign(
  {
    if (i >= max_size())
    {
-      this->set_size(i);
+      this->size_impl(i);
      term();
      detail::throw_exception<std::length_error>("n > max_size()");
    }
    traits_type::assign(*ptr, *first);
  }
-  this->set_size(ptr - data());
+  this->size_impl(ptr - data());
  return term();
 }

@@ -6567,7 +6706,10 @@ insert(
  const auto index = pos - curr_data;
  traits_type::move(&curr_data[index + count], &curr_data[index], curr_size - index + 1);
  traits_type::assign(&curr_data[index], count, ch);
-  this->set_size(curr_size + count);
+  this->size_impl(curr_size + count);
+#if defined(__clang__) && __clang_major__ == 3 && __clang_minor__ == 7
+  term();
+#endif
  return &curr_data[index];
 }

@@ -6620,7 +6762,7 @@ insert(
      traits_type::copy(dest, src, count);
    }
  }
-  this->set_size(curr_size + count);
+  this->size_impl(curr_size + count);
  return curr_data + index;
 }

@@ -6644,7 +6786,7 @@ insert(
  const auto count = read_back(false, first, last);
  const std::size_t index = pos - curr_data;
  std::rotate(&curr_data[index], &curr_data[curr_size + 1], &curr_data[curr_size + count + 1]);
-  this->set_size(curr_size + count);
+  this->size_impl(curr_size + count);
  return curr_data + index;
 }

@@ -6660,7 +6802,7 @@ erase(
  const auto curr_data = data();
  const std::size_t index = first - curr_data;
  traits_type::move(&curr_data[index], last, (end() - last) + 1);
-  this->set_size(size() - std::size_t(last - first));
+  this->size_impl(size() - std::size_t(last - first));
  return curr_data + index;
 }

@@ -6676,7 +6818,7 @@ push_back(
    detail::throw_exception<std::length_error>(
      "curr_size >= max_size()");
  traits_type::assign(data()[curr_size], ch);
-  this->set_size(curr_size + 1);
+  this->size_impl(curr_size + 1);
  term();
 }

@@ -6694,7 +6836,7 @@ append(
    detail::throw_exception<std::length_error>(
      "count > max_size() - size()");
  traits_type::assign(end(), count, ch);
-  this->set_size(curr_size + count);
+  this->size_impl(curr_size + count);
  return term();
 }

@@ -6712,7 +6854,7 @@ append(
    detail::throw_exception<std::length_error>(
      "count > max_size() - size()");
  traits_type::copy(end(), s, count);
-  this->set_size(curr_size + count);
+  this->size_impl(curr_size + count);
  return term();
 }

@@ -6728,7 +6870,7 @@ resize(size_type n, value_type c)
  const auto curr_size = size();
  if(n > curr_size)
    traits_type::assign(data() + curr_size, n - curr_size, c);
-  this->set_size(n);
+  this->size_impl(n);
  term();
 }

@@ -6748,7 +6890,7 @@ resize_and_overwrite(
  CharT* p = data();
  const auto new_size = std::move(op)(p, n);
  BOOST_STATIC_STRING_ASSERT(new_size >= 0 && size_type(new_size) <= n);
-  this->set_size(size_type(new_size));
+  this->size_impl(size_type(new_size));
  term();
 }

@@ -6760,9 +6902,9 @@ swap(basic_static_string& s) noexcept
 {
  const auto curr_size = size();
  basic_static_string tmp(s);
-  s.set_size(curr_size);
+  s.size_impl(curr_size);
  traits_type::copy(&s.data()[0], data(), curr_size + 1);
-  this->set_size(tmp.size());
+  this->size_impl(tmp.size());
  traits_type::copy(data(), tmp.data(), size() + 1);
 }

@@ -6781,10 +6923,8 @@ swap(basic_static_string<M, CharT, Traits>& s)
    detail::throw_exception<std::length_error>(
      "s.size() > max_size()");
  basic_static_string tmp(s);
-  s.set_size(curr_size);
-  traits_type::copy(&s.data()[0], data(), curr_size + 1);
-  this->set_size(tmp.size());
-  traits_type::copy(data(), &tmp.data()[0], size() + 1);
+  s.assign_unchecked(data(), curr_size);
+  assign_unchecked(tmp.data(), tmp.size());
 }

 template<std::size_t N, typename CharT, typename Traits>
@@ -6807,7 +6947,7 @@ replace(
  const auto pos = i1 - curr_data;
  traits_type::move(&curr_data[pos + n], i2, (end() - i2) + 1);
  traits_type::assign(&curr_data[pos], n, c);
-  this->set_size((curr_size - n1) + n);
+  this->size_impl((curr_size - n1) + n);
  return *this;
 }

@@ -6868,7 +7008,7 @@ replace(
      traits_type::move(&curr_data[pos + n2], &curr_data[pos + n1], curr_size - pos - n1 + 1);
    }
  }
-  this->set_size((curr_size - n1) + n2);
+  this->size_impl((curr_size - n1) + n2);
  return *this;
 }

@@ -6900,7 +7040,7 @@ replace(
  // Move everything from the end of the splice point to the end of the rotated string to
  // the begining of the splice point
  traits_type::move(&curr_data[pos + n2], &curr_data[pos + n2 + n1], ((curr_size - n1) + n2) - pos);
-  this->set_size((curr_size - n1) + n2);
+  this->size_impl((curr_size - n1) + n2);
  return *this;
 }

@@ -7072,7 +7212,7 @@ replace_unchecked(
      "replaced string exceeds max_size()");
  traits_type::move(&curr_data[pos + n2], i2, (end() - i2) + 1);
  traits_type::copy(&curr_data[pos], s, n2);
-  this->set_size((curr_size - n1) + n2);
+  this->size_impl((curr_size - n1) + n2);
  return *this;
 }

@@ -7094,7 +7234,7 @@ insert_unchecked(
  const std::size_t index = pos - curr_data;
  traits_type::move(&curr_data[index + count], pos, (end() - pos) + 1);
  traits_type::copy(&curr_data[index], s, count);
-  this->set_size(curr_size + count);
+  this->size_impl(curr_size + count);
  return curr_data + index;
 }

--- a/meta/libraries.json
+++ b/meta/libraries.json
@@ -7,13 +7,13 @@
    ],
    "description": "A fixed capacity dynamically sized string.",
    "category": [
-        "Container",
+        "Containers",
        "String"
    ],
    "maintainers": [
-        "Krystian Stasiowski <sdkrystian@gmail.com>",
        "Alan de Freitas <alandefreitas@gmail.com>",
-        "Vinnie Falco <vinnie.falco@gmail.com>"
+        "Vinnie Falco <vinnie.falco@gmail.com>",
+        "Gennaro Prota <gennaro.prota@gmail.com>"
    ],
    "cxxstd": "11"
 }
--- a/test/compile_fail.hpp
+++ b/test/compile_fail.hpp
@@ -4,16 +4,6 @@
 namespace boost {
 namespace static_strings {

-static_assert(std::is_base_of<
-  detail::static_string_base<0, char, std::char_traits<char>>,
-              static_string<0>>::value,
-              "the zero size optimization shall be used for N = 0");
-
-static_assert(std::is_base_of<
-  detail::static_string_base<(std::numeric_limits<char>::max)() + 1, char, std::char_traits<char>>,
-              static_string<(std::numeric_limits<char>::max)() + 1>>::value,
-              "the minimum size type optimization shall be used for N > 0");
-
 static_assert(!detail::is_input_iterator<int>::value, "is_input_iterator is incorrect");
 static_assert(!detail::is_input_iterator<double>::value, "is_input_iterator is incorrect");
 static_assert(detail::is_input_iterator<int*>::value, "is_input_iterator is incorrect");
--- a/test/constexpr_tests.hpp
+++ b/test/constexpr_tests.hpp
@@ -22,38 +22,77 @@ struct cxper_char_traits
  using int_type = int;
  using state_type = std::mbstate_t;

-  static constexpr void assign(char_type& a, const char_type& b) noexcept { a = b;  }
-  static constexpr bool eq(char_type a, char_type b) noexcept { return a == b; }
-  static constexpr bool lt(char_type a, char_type b) noexcept { return a < b; }
+  static constexpr void assign(char_type& a, const char_type& b) noexcept
+  {
+    a = b;
+  }
+
+  static constexpr bool eq(char_type a, char_type b) noexcept
+  {
+    return a == b;
+  }
+
+  static constexpr bool lt(char_type a, char_type b) noexcept
+  {
+    return a < b;
+  }
+
+  static constexpr int compare(const char_type* a, const char_type* b, std::size_t n)
+  {
+    for (; n--; ++a, ++b)
+    {
+      if(lt(*a, *b))
+        return 1;
+      else if(lt(*b, *a))
+        return -1;
+    }
+    return 0;
+  }

-  static constexpr int compare(const char_type*, const char_type*, std::size_t) { return 0; }
  static constexpr std::size_t length(const char_type* s)
  {
-    std::size_t n = 0;
-    while (*(s++));
-    return n;
+    auto ptr = s;
+    while (!eq(*ptr, char_type()))
+      ++ptr;
+    return ptr - s;
  }
-  static constexpr const char_type* find(const char_type*, std::size_t, const char_type&){ return 0; }
+
+  static constexpr const char_type* find(const char_type* s, std::size_t n, const char_type& ch)
+  {
+    for (; n--; ++s)
+    {
+      if (eq(*s, ch))
+        return s;
+    }
+    return nullptr;
+  }
+
  static constexpr char_type* move(char_type* dest, const char_type* src, std::size_t n)
  {
-    const auto temp = dest;
-    while (n--)
-      *(dest++) = *(src++);
-    return temp;
+    // This implementation does not handle overlapping ranges where
+    // dest > src. A correct implementation would need to detect this
+    // case and copy backwards, but detecting overlap requires pointer
+    // comparisons that many of the tested compiles (incorrectly) refuse
+    // in constant expressions.
+    //
+    // Since cxper_char_traits is only used for testing constexpr
+    // functionality and the tests do not exercise overlapping moves
+    // where dest > src, this simple forward copy is sufficient.
+    return copy(dest, src, n);
  }
+
  static constexpr char_type* copy(char_type* dest, const char_type* src, std::size_t n)
  {
-    const auto temp = dest;
-    while (n--)
-      *(dest++) = *(src++);
-    return temp;
+    for (auto ptr = dest; n--;)
+      assign(*ptr++, *src++);
+    return dest;
  }
+
  static constexpr char_type* assign(char_type* dest, std::size_t n, char_type ch)
  {
-    const auto temp = dest;
-    while (n--)
-      *(dest++) = ch;
-    return temp;
+    for (auto ptr = dest; n--;)
+      assign(*ptr++, ch);
+    return dest;
  }
 };
 #else
@@ -67,6 +106,23 @@ bool
 testConstantEvaluation()
 {
 #ifdef BOOST_STATIC_STRING_CPP20
+
+  // Check construction in a constexpr context
+  constexpr basic_static_string s("hello");
+  static_assert(s.size() == 5);
+  static_assert(s.static_capacity == 5);
+  static_assert(s == "hello");
+
+  // Check assignment in a constexpr context
+  constexpr auto s2 =
+  []()
+  {
+    basic_static_string s("hello");
+    s = "world";
+    return s;
+  }();
+  static_assert(s2 == "world");
+
  // c++20 constexpr tests
  cstatic_string a;
  cstatic_string b(1, 'a');
@@ -171,8 +227,10 @@ testConstantEvaluation()

  a.substr(0);

+#ifdef BOOST_STATIC_STRING_HAS_ANY_STRING_VIEW
  // subview
  a.subview(0);
+#endif

  // copy
  char k[20]{};
@@ -198,7 +256,8 @@ testConstantEvaluation()
  a.replace(a.begin(), a.end(), a.begin(), a.end());
  a.replace(a.begin(), a.end(), {'a'});

-#ifdef BOOST_STATIC_STRING_IS_CONST_EVAL
+#if defined(BOOST_STATIC_STRING_IS_CONST_EVAL) \
+        && !defined(BOOST_STATIC_STRING_CONSTEXPR_PTR_CMP_BROKEN)
  a.clear();
  a.replace(a.begin(), a.end(), "a");
  a.replace(a.begin(), a.end(), "a", 1);
@@ -386,7 +445,8 @@ testConstantEvaluation()
  a.replace(a.begin(), a.end(), a.begin(), a.end());
  a.replace(a.begin(), a.end(), {'a'});

-#ifdef BOOST_STATIC_STRING_IS_CONST_EVAL
+#if defined(BOOST_STATIC_STRING_IS_CONST_EVAL) \
+        && !defined(BOOST_STATIC_STRING_CONSTEXPR_PTR_CMP_BROKEN)
  a.clear();
  a.replace(a.begin(), a.end(), "a");
  a.replace(a.begin(), a.end(), "a", 1);
@@ -558,7 +618,8 @@ testConstantEvaluation()
  a.replace(a.begin(), a.end(), a.begin(), a.end());
  a.replace(a.begin(), a.end(), {'a'});

-#ifdef BOOST_STATIC_STRING_IS_CONST_EVAL
+#if defined(BOOST_STATIC_STRING_IS_CONST_EVAL) \
+        && !defined(BOOST_STATIC_STRING_CONSTEXPR_PTR_CMP_BROKEN)
  a.clear();
  a.replace(a.begin(), a.end(), "a");
  a.replace(a.begin(), a.end(), "a", 1);
@@ -605,5 +666,28 @@ testConstantEvaluation()
    cstatic_string().empty();
 #endif
 }
+
+#if __cpp_nontype_template_args >= 201911L
+
+template<basic_static_string<32, char, cxper_char_traits> X>
+struct nttp_primary
+{
+  static constexpr bool value = false;
+};
+
+template<>
+struct nttp_primary<"test string">
+{
+  static constexpr bool value = true;
+};
+
+static_assert(!nttp_primary<"random string">::value,
+  "structural equality broken");
+
+static_assert(nttp_primary<"test string">::value,
+  "structural equality broken");
+
+#endif
+
 } // static_strings
-} // boost
+} // boost
--- a/test/static_string.cpp
+++ b/test/static_string.cpp
@@ -919,14 +919,14 @@ testElements()
        BOOST_TEST(std::memcmp(
            s.c_str(), "123\0", 4) == 0);
    }
-#ifdef BOOST_STATIC_ASSERT_HAS_STRING_VIEW
+#ifdef BOOST_STATIC_STRING_HAS_STRING_VIEW
    {
        static_string<3> s("123");
        string_view sv = s;
        BOOST_TEST(static_string<5>(sv) == "123");
    }
 #endif
-#ifdef BOOST_STATIC_ASSERT_HAS_STD_STRING_VIEW
+#ifdef BOOST_STATIC_STRING_HAS_STD_STRING_VIEW
    {
        static_string<3> s("123");
        std::string_view sv = s;
@@ -7430,7 +7430,12 @@ testResizeAndOverwrite()
      5,
      [](char* buf, std::size_t) -> std::size_t
      {
-        std::strcpy(buf, "Hello");
+        // Don't use std::strcpy() to avoid a MSVC C4996 warning.
+        buf[0] = 'H';
+        buf[1] = 'e';
+        buf[2] = 'l';
+        buf[3] = 'l';
+        buf[4] = 'o';
        return 5;
      }
    );
Author	SHA1	Message	Date
Gennaro Prota	e9313dc331	Add an experimental basic_static_cstring template in example/ This introduces an alternative to basic_static_string designed for use in POD types: Trivially copyable, having a sizeof == N + 1, with no embedded NULs. Placed in example/ to gather user feedback before committing to a public API. See issue #23.	2025-12-19 19:32:30 +01:00
Gennaro Prota	0c5e5b8e58	Fix our deduction guide	2025-12-19 18:26:40 +01:00
Gennaro Prota	6f0c00b268	Work around a Clang 3.7 bug affecting constexpr insert() The iterator-based insert(const_iterator, size_type, value_type) function relies on traits_type::move() to shift the existing null terminator to its new position. Clang 3.7's constexpr evaluator does not handle this correctly, causing the following test to fail: static_string<3>{"ab"}.insert(2, 1, 'c') == "abc" Add an explicit term() call, guarded by a preprocessor conditional for Clang 3.7, to ensure proper null termination.	2025-12-19 18:23:33 +01:00
Gennaro Prota	2175496c55	Condition the NTTP tests on __cpp_nontype_template_args They were conditioned on detection of C++20 via __cplusplus, but Clang 10 and 11 don't support class types as NTTP, even though they report C++20 via __cplusplus when -std=c++20 is used.	2025-12-19 18:23:33 +01:00
Gennaro Prota	aee3c62957	Apply the workaround in the previous commit to Clang 3.7 and 9-19, too Reason: They have the same issue as GCC 9.	2025-12-19 18:23:33 +01:00
Gennaro Prota	0e28b358dc	Work around GCC 9 rejecting a legitimate pointer comparison in a constexpr context	2025-12-19 18:23:33 +01:00
Gennaro Prota	4dcfb39494	Replace the implementation of cxper_char_traits::move() with a simpler one Reason: See the new code comment.	2025-12-19 18:23:33 +01:00
Gennaro Prota	4bf6461ca1	Work around a bug in GCC 5-10 GCC 5-10 incorrectly complain about our nested classes being private. So, make them public.	2025-12-19 18:23:33 +01:00
Krystian Stasiowski	67efdf6a9b	Make basic_static_string usable as a NTTP	2025-12-19 18:23:33 +01:00
Krystian Stasiowski	3a410b8472	Add build directory and CMake preset files to .gitignore	2025-12-19 18:23:33 +01:00
Gennaro Prota	bf988466f8	Work around GCC (libstdc++) bug #113200 See the previous commit. This simple fix avoids calling Traits::move(), which is where the bug resides. This closes issue #55.	2025-12-16 10:30:33 +01:00
Gennaro Prota	a526ebd1f6	Check that basic_static_string can be constructed and assigned from a C-style string in a constexpr context This triggers a libstdc++ issue which was fixed in GCC 12.4 and 13.3: <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113200>. If our CI shows we bump into that bug, we'll add a workaround.	2025-12-16 10:30:33 +01:00
Gennaro Prota	2f8c7a69ea	Update the library metadata: Remove Krystian, add myself as a maintainer	2025-12-15 14:25:26 +01:00
Gennaro Prota	c915934529	Fix four occorrences of a typo ("arugment") in the Javadoc comments	2025-11-14 12:03:00 +01:00
Gennaro Prota	10b5491104	Avoid two C4244 warnings from MSVC	2025-11-05 11:30:41 +01:00
Alexander Grund	a58319dbdd	Switch boost.io to boost.org	2025-10-24 11:59:10 +02:00
Alexander Grund	4c84b61975	README: Replace travis badges by GHA badges	2025-10-24 11:59:10 +02:00
Alexander Grund	fbd6051165	Update Link to regression test matrix in README	2025-10-24 11:59:10 +02:00
Alexander Grund	db1ea76a17	Fix required CMake version `source_group(TREE` requires CMake 3.8	2025-10-24 11:58:47 +02:00
Alexander Grund	ee172b86fd	Try standalone only with >=C++17	2025-10-24 11:57:55 +02:00
Alexander Grund	bd3dd01259	Update Drone from Boost.CI	2025-10-24 11:57:55 +02:00
Gennaro Prota	a841869405	Remove a use of std::strcpy() to avoid a C4996 warning from MSVC	2025-10-24 11:00:21 +02:00
Alexander Grund	3613e9578d	Fix standalone build with Clang The config.hpp uses `BOOST_LIBSTDCXX_VERSION` which isn't defined in standalone mode so `BOOST_STATIC_STRING_NO_CXX17_HDR_STRING_VIEW` will be defined. This then causes build failures for code expecting the availability of string_view.	2025-10-24 10:11:37 +02:00
Alexander Grund	6f17b60377	Guard test requiring string_view	2025-10-24 10:11:37 +02:00
Gennaro Prota	815678e1e7	CI: Test C++26/2c again	2025-10-23 16:49:48 +02:00
Gennaro Prota	2cc22bf5a8	Align to_static_[w]string() with C++26 std::to_[w]string() C++26 specifies that std::to_string() and std::to_wstring() format floating point values as if using std::format(). This commit updates the internal conversion helpers to match that behavior, using std::format_to_n() for efficient, allocation-free formatting directly into the static_string/static_wstring buffer. Fallbacks using snprintf()/swprintf() remain active for pre-C++26 builds. This ensures consistent formatting across standard and Boost APIs.	2025-10-23 16:49:48 +02:00
Gennaro Prota	d6f976a7df	Fix the sizes of the strings returned by to_static_string() and to_static_wstring() for floating point values	2025-10-23 16:49:48 +02:00
Gennaro Prota	7b564d8d26	Fix two macro names in the unit tests	2025-10-22 19:18:39 +02:00
Gennaro Prota	3c37deed99	Fix the previous commit	2025-10-22 19:11:09 +02:00
Gennaro Prota	34ef5c45be	Remove an unused dependency on Boost.StaticAssert This closes issue #73.	2025-10-22 19:06:12 +02:00
Kenneth Reitz	0f34644488	Update libraries.json /s/container/containers The other libraries reference "containers" instead of "container"	2025-10-22 18:48:18 +02:00
Dmitry Arkhipov	4c27826548	use Python version of Docca	2025-10-22 18:35:38 +02:00