From a9a295e4aa213a0430f0058b3e21299641072f56 Mon Sep 17 00:00:00 2001
From: "Markus F.X.J. Oberhumer" <markus@oberhumer.com>
Date: Wed, 4 Jan 2023 01:36:20 +0100
Subject: [PATCH] Avoid -Wzero-as-null-pointer-constant warnings.

---
 include/boost/pfr/core.hpp                    |  4 ++--
 include/boost/pfr/detail/core14_classic.hpp   | 16 ++++++++--------
 include/boost/pfr/detail/core17_generated.hpp |  4 ++--
 include/boost/pfr/detail/unsafe_declval.hpp   |  2 +-
 misc/generate_cpp17.py                        |  4 ++--
 5 files changed, 15 insertions(+), 15 deletions(-)

diff --git a/include/boost/pfr/core.hpp b/include/boost/pfr/core.hpp
index 08837e6..f3585bb 100644
--- a/include/boost/pfr/core.hpp
+++ b/include/boost/pfr/core.hpp
@@ -66,7 +66,7 @@ constexpr auto get(T&, std::enable_if_t<!std::is_assignable<T, T>::value>* = nul
 
 /// \overload get
 template <std::size_t I, class T>
-constexpr auto get(T&& val, std::enable_if_t< std::is_rvalue_reference<T&&>::value>* = 0) noexcept {
+constexpr auto get(T&& val, std::enable_if_t< std::is_rvalue_reference<T&&>::value>* = nullptr) noexcept {
     return std::move(detail::sequence_tuple::get<I>( detail::tie_as_tuple(val) ));
 }
 
@@ -159,7 +159,7 @@ constexpr auto structure_tie(T&, std::enable_if_t<!std::is_assignable<T, T>::val
 
 /// \overload structure_tie
 template <class T>
-constexpr auto structure_tie(T&&, std::enable_if_t< std::is_rvalue_reference<T&&>::value>* = 0) noexcept {
+constexpr auto structure_tie(T&&, std::enable_if_t< std::is_rvalue_reference<T&&>::value>* = nullptr) noexcept {
     static_assert(sizeof(T) && false, "====================> Boost.PFR: Calling boost::pfr::structure_tie on rvalue references is forbidden");
     return 0;
 }
diff --git a/include/boost/pfr/detail/core14_classic.hpp b/include/boost/pfr/detail/core14_classic.hpp
index 7cd4257..183337c 100644
--- a/include/boost/pfr/detail/core14_classic.hpp
+++ b/include/boost/pfr/detail/core14_classic.hpp
@@ -118,16 +118,16 @@ template <class Type> constexpr std::size_t type_to_id(identity<const Type*>) no
 template <class Type> constexpr std::size_t type_to_id(identity<const volatile Type*>) noexcept;
 template <class Type> constexpr std::size_t type_to_id(identity<volatile Type*>) noexcept;
 template <class Type> constexpr std::size_t type_to_id(identity<Type&>) noexcept;
-template <class Type> constexpr std::size_t type_to_id(identity<Type>, std::enable_if_t<std::is_enum<Type>::value>* = 0) noexcept;
-template <class Type> constexpr std::size_t type_to_id(identity<Type>, std::enable_if_t<std::is_empty<Type>::value>* = 0) noexcept;
-template <class Type> constexpr std::size_t type_to_id(identity<Type>, std::enable_if_t<std::is_union<Type>::value>* = 0) noexcept;
+template <class Type> constexpr std::size_t type_to_id(identity<Type>, std::enable_if_t<std::is_enum<Type>::value>* = nullptr) noexcept;
+template <class Type> constexpr std::size_t type_to_id(identity<Type>, std::enable_if_t<std::is_empty<Type>::value>* = nullptr) noexcept;
+template <class Type> constexpr std::size_t type_to_id(identity<Type>, std::enable_if_t<std::is_union<Type>::value>* = nullptr) noexcept;
 template <class Type> constexpr size_array<sizeof(Type) * 3> type_to_id(identity<Type>, std::enable_if_t<!std::is_enum<Type>::value && !std::is_empty<Type>::value && !std::is_union<Type>::value>* = 0) noexcept;
 
-template <std::size_t Index> constexpr auto id_to_type(size_t_<Index >, if_extension<Index, native_const_ptr_type> = 0) noexcept;
-template <std::size_t Index> constexpr auto id_to_type(size_t_<Index >, if_extension<Index, native_ptr_type> = 0) noexcept;
-template <std::size_t Index> constexpr auto id_to_type(size_t_<Index >, if_extension<Index, native_const_volatile_ptr_type> = 0) noexcept;
-template <std::size_t Index> constexpr auto id_to_type(size_t_<Index >, if_extension<Index, native_volatile_ptr_type> = 0) noexcept;
-template <std::size_t Index> constexpr auto id_to_type(size_t_<Index >, if_extension<Index, native_ref_type> = 0) noexcept;
+template <std::size_t Index> constexpr auto id_to_type(size_t_<Index >, if_extension<Index, native_const_ptr_type> = nullptr) noexcept;
+template <std::size_t Index> constexpr auto id_to_type(size_t_<Index >, if_extension<Index, native_ptr_type> = nullptr) noexcept;
+template <std::size_t Index> constexpr auto id_to_type(size_t_<Index >, if_extension<Index, native_const_volatile_ptr_type> = nullptr) noexcept;
+template <std::size_t Index> constexpr auto id_to_type(size_t_<Index >, if_extension<Index, native_volatile_ptr_type> = nullptr) noexcept;
+template <std::size_t Index> constexpr auto id_to_type(size_t_<Index >, if_extension<Index, native_ref_type> = nullptr) noexcept;
 
 
 ///////////////////// Definitions of type_to_id and id_to_type for fundamental types
diff --git a/include/boost/pfr/detail/core17_generated.hpp b/include/boost/pfr/detail/core17_generated.hpp
index ea9dbfb..560d0d4 100644
--- a/include/boost/pfr/detail/core17_generated.hpp
+++ b/include/boost/pfr/detail/core17_generated.hpp
@@ -59,14 +59,14 @@ constexpr auto tie_as_tuple(T& /*val*/, size_t_<0>) noexcept {
 }
 
 template <class T>
-constexpr auto tie_as_tuple(T& val, size_t_<1>, std::enable_if_t<std::is_class< std::remove_cv_t<T> >::value>* = 0) noexcept {
+constexpr auto tie_as_tuple(T& val, size_t_<1>, std::enable_if_t<std::is_class< std::remove_cv_t<T> >::value>* = nullptr) noexcept {
   auto& [a] = const_cast<std::remove_cv_t<T>&>(val); // ====================> Boost.PFR: User-provided type is not a SimpleAggregate.
   return ::boost::pfr::detail::make_tuple_of_references(detail::workaround_cast<T, decltype(a)>(a));
 }
 
 
 template <class T>
-constexpr auto tie_as_tuple(T& val, size_t_<1>, std::enable_if_t<!std::is_class< std::remove_cv_t<T> >::value>* = 0) noexcept {
+constexpr auto tie_as_tuple(T& val, size_t_<1>, std::enable_if_t<!std::is_class< std::remove_cv_t<T> >::value>* = nullptr) noexcept {
   return ::boost::pfr::detail::make_tuple_of_references( val );
 }
 
diff --git a/include/boost/pfr/detail/unsafe_declval.hpp b/include/boost/pfr/detail/unsafe_declval.hpp
index 62404c5..8afb4fc 100644
--- a/include/boost/pfr/detail/unsafe_declval.hpp
+++ b/include/boost/pfr/detail/unsafe_declval.hpp
@@ -24,7 +24,7 @@ template <class T>
 constexpr T unsafe_declval() noexcept {
     report_if_you_see_link_error_with_this_function();
 
-    typename std::remove_reference<T>::type* ptr = 0;
+    typename std::remove_reference<T>::type* ptr = nullptr;
     ptr += 42; // suppresses 'null pointer dereference' warnings
     return static_cast<T>(*ptr);
 }
diff --git a/misc/generate_cpp17.py b/misc/generate_cpp17.py
index 5350e07..98c57bc 100644
--- a/misc/generate_cpp17.py
+++ b/misc/generate_cpp17.py
@@ -76,14 +76,14 @@ constexpr auto tie_as_tuple(T& /*val*/, size_t_<0>) noexcept {
 }
 
 template <class T>
-constexpr auto tie_as_tuple(T& val, size_t_<1>, std::enable_if_t<std::is_class< std::remove_cv_t<T> >::value>* = 0) noexcept {
+constexpr auto tie_as_tuple(T& val, size_t_<1>, std::enable_if_t<std::is_class< std::remove_cv_t<T> >::value>* = nullptr) noexcept {
   auto& [a] = const_cast<std::remove_cv_t<T>&>(val); // ====================> Boost.PFR: User-provided type is not a SimpleAggregate.
   return ::boost::pfr::detail::make_tuple_of_references(detail::workaround_cast<T, decltype(a)>(a));
 }
 
 
 template <class T>
-constexpr auto tie_as_tuple(T& val, size_t_<1>, std::enable_if_t<!std::is_class< std::remove_cv_t<T> >::value>* = 0) noexcept {
+constexpr auto tie_as_tuple(T& val, size_t_<1>, std::enable_if_t<!std::is_class< std::remove_cv_t<T> >::value>* = nullptr) noexcept {
   return ::boost::pfr::detail::make_tuple_of_references( val );
 }