gcc-12 warnings for charconv

[anarthal]

The following:

#include <boost/decimal.hpp>

using namespace boost::decimal;

void f(decimal32 v)
{
    char buff[64]{};
    auto r = boost::decimal::to_chars(buff, buff + sizeof(buff), v);
    *r.ptr = 0;
    std::cout << buff << std::endl;
}

int main() { f(1e-40_df); }

Emits the following warning:

[build] In file included from /usr/include/string.h:535,
[build]                  from /usr/include/c++/12/cstring:42,
[build]                  from [redacted]/boost-root/libs/decimal/include/boost/decimal/detail/wide-integer/uintwide_t.hpp:28,
[build]                  from [redacted]/boost-root/libs/decimal/include/boost/decimal/detail/emulated128.hpp:13,
[build]                  from [redacted]/boost-root/libs/decimal/include/boost/decimal/detail/type_traits.hpp:11,
[build]                  from [redacted]/boost-root/libs/decimal/include/boost/decimal/detail/attributes.hpp:9,
[build]                  from [redacted]/boost-root/libs/decimal/include/boost/decimal/decimal32.hpp:9,
[build]                  from [redacted]/boost-root/libs/decimal/include/boost/decimal.hpp:27,
[build]                  from [redacted]/boost-root/libs/mysql/example/main.cpp:1:
[build] In function ‘void* memset(void*, int, size_t)’,
[build]     inlined from ‘constexpr boost::decimal::to_chars_result boost::decimal::detail::to_chars_fixed_impl(char*, char*, const TargetDecimalType&, boost::decimal::chars_format, int) [with TargetDecimalType = boost::decimal::decimal32]’ at [redacted]/boost-root/libs/decimal/include/boost/decimal/charconv.hpp:576:24,
[build]     inlined from ‘constexpr boost::decimal::to_chars_result boost::decimal::detail::to_chars_impl(char*, char*, TargetDecimalType, boost::decimal::chars_format, int) [with TargetDecimalType = boost::decimal::decimal32]’ at [redacted]/boost-root/libs/decimal/include/boost/decimal/charconv.hpp:865:47,
[build]     inlined from ‘constexpr boost::decimal::to_chars_result boost::decimal::to_chars(char*, char*, decimal32)’ at [redacted]/boost-root/libs/decimal/include/boost/decimal/charconv.hpp:914:33,
[build]     inlined from ‘void f(boost::decimal::decimal32)’ at [redacted]/boost-root/libs/mysql/example/main.cpp:8:38:
[build] /usr/include/x86_64-linux-gnu/bits/string_fortified.h:59:33: error: ‘void* __builtin___memset_chk(void*, int, long unsigned int, long unsigned int)’ specified bound 18446744073709551615 exceeds maximum object size 9223372036854775807 [-Werror=stringop-overflow=]
[build]    59 |   return __builtin___memset_chk (__dest, __ch, __len,
[build]       |          ~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~
[build]    60 |                                  __glibc_objsize0 (__dest));

Command line:

/usr/bin/g++-12  -I[redacted]/boost-root/libs/decimal/include  -O3 -DNDEBUG -std=gnu++23 -Wextra -Werror  -c main.cpp

This is likely spurious, and can be suppressed with pragma warning.

[mborland]

I believe this is handled in #796