From 3fd285c014be5ff33ac290e9eb769813751deb63 Mon Sep 17 00:00:00 2001
From: Zach Laine <whatwasthataddress@gmail.com>
Date: Sun, 1 Dec 2024 20:26:18 -0600
Subject: [PATCH] Correct memory safety issue in converting token iteratos to
 underlying iterators.

See #202.
---
 include/boost/parser/detail/printing_impl.hpp | 16 +++++-----------
 include/boost/parser/error_handling.hpp       | 12 +++---------
 include/boost/parser/lexer.hpp                | 12 ++++++++++++
 3 files changed, 20 insertions(+), 20 deletions(-)

diff --git a/include/boost/parser/detail/printing_impl.hpp b/include/boost/parser/detail/printing_impl.hpp
index d46e0af1..daa0a9df 100644
--- a/include/boost/parser/detail/printing_impl.hpp
+++ b/include/boost/parser/detail/printing_impl.hpp
@@ -1014,10 +1014,8 @@ namespace boost { namespace parser { namespace detail {
         if (!detail::do_trace(flags_))
             return;
         if constexpr (is_token_iter_v<Iter>) {
-            auto const initial_first = first_.range_begin();
-            auto const first = initial_first + (*first_).underlying_position();
-            auto const last = first_.range_end();
-            detail::trace_prefix(os, first, last, context_, name_);
+            detail::trace_prefix(
+                os, first_.base(), first_.range_end(), context_, name_);
         } else {
             detail::trace_prefix(os, first_, last_, context_, name_);
         }
@@ -1032,14 +1030,10 @@ namespace boost { namespace parser { namespace detail {
     scoped_trace_t<DoTrace, Iter, Sentinel, Context, Attribute>::
         ~scoped_trace_t()
     {
-        if constexpr (is_token_iter_v<Iter>) {
-            auto const initial_first = first_.range_begin();
-            auto const first = initial_first + (*first_).underlying_position();
-            auto const last = first_.range_end();
-            impl(initial_first, first, last);
-        } else {
+        if constexpr (is_token_iter_v<Iter>)
+            impl(first_.range_begin(), first_.base(), first_.range_end());
+        else
             impl(initial_first_, first_, last_);
-        }
     }
 
 }}}
diff --git a/include/boost/parser/error_handling.hpp b/include/boost/parser/error_handling.hpp
index 23a4a6cd..8645c02f 100644
--- a/include/boost/parser/error_handling.hpp
+++ b/include/boost/parser/error_handling.hpp
@@ -192,16 +192,10 @@ namespace boost { namespace parser {
         template<typename I, typename S>
         auto normalize_iterators_impl(I first, I it, S last)
         {
-            if constexpr (detail::is_token_iter_v<I>) {
-                auto const underlying_first = it.range_begin();
-                auto const underlying_it =
-                    underlying_first + (*it).underlying_position();
-                auto const underlying_last = it.range_end();
-                return std::tuple(
-                    underlying_first, underlying_it, underlying_last);
-            } else {
+            if constexpr (detail::is_token_iter_v<I>)
+                return std::tuple(it.range_begin(), it.base(), it.range_end());
+            else
                 return std::tuple(first, it, last);
-            }
         }
     }
 
diff --git a/include/boost/parser/lexer.hpp b/include/boost/parser/lexer.hpp
index 42e886f4..44dbef46 100644
--- a/include/boost/parser/lexer.hpp
+++ b/include/boost/parser/lexer.hpp
@@ -941,6 +941,9 @@ namespace boost { namespace parser {
 
             constexpr token_type const & operator*() const
             {
+                BOOST_PARSER_DEBUG_ASSERT(
+                    token_offset_ - parent_->base_token_offset_ <
+                    (BOOST_PARSER_TOKEN_POSITION_TYPE)parent_->tokens_.size());
                 return parent_
                     ->tokens_[token_offset_ - parent_->base_token_offset_];
             }
@@ -951,6 +954,15 @@ namespace boost { namespace parser {
                 return token_offset_ == rhs.token_offset_;
             }
 
+            auto base() const
+            {
+                return token_offset_ - parent_->base_token_offset_ ==
+                               (BOOST_PARSER_TOKEN_POSITION_TYPE)
+                                   parent_->tokens_.size()
+                           ? range_end()
+                           : range_begin() + (**this).underlying_position();
+            }
+
             auto range_begin() const
             {
                 return std::ranges::begin(parent_->base_);