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<format>: Fix signed/unsigned mismatch in _In_bounds#1875

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StephanTLavavej merged 1 commit intomicrosoft:mainfrom
StephanTLavavej:format_in_range
Apr 23, 2021
Merged

<format>: Fix signed/unsigned mismatch in _In_bounds#1875
StephanTLavavej merged 1 commit intomicrosoft:mainfrom
StephanTLavavej:format_in_range

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@StephanTLavavej StephanTLavavej commented Apr 23, 2021

This reimplements <format>'s _In_bounds with C++20 in_range to fix VSO-1314150 "[RWC][Regression][prod/fe][std:c++latest] Google_Snappy/Glslang/ITK failed with warning C4018". (I haven't personally reproed this warning, but the messages clearly indicate _In_bounds, and C++20 in_range should completely avoid such warnings in addition to having an optimal implementation.)

We need _Make_standard_integer to map any character types (char, wchar_t, char8_t, char16_t, char32_t) to the signed/unsigned integer types ([unsigned] char/short/int/long/long long) with the same signedness/width, because C++20 in_range requires that. We specifically don't handle bool, which should never be given to _In_bounds (I checked the usage) and is rejected with a guaranteed static_assert by C++20 in_range.

warning C4018: '<=': signed/unsigned mismatch 
gtest-all.i(127456): error C2220: the following warning is treated as an error
gtest-all.i(127560): note: see reference to function template instantiation 'bool std::_In_bounds<_CharT,_Integral>(const _Ty)' being compiled
        with
        [
            _CharT=char,
            _Integral=int,
            _Ty=int
        ]
gtest-all.i(127669): note: see reference to function template instantiation '_OutputIt std::_Write_integral<_CharT,std::back_insert_iterator<std::string>,_Integral>(_OutputIt,const _Integral,std::_Basic_format_specs<_CharT>,std::locale)' being compiled
        with
        [
            _OutputIt=std::back_insert_iterator<std::string>,
            _CharT=char,
            _Integral=int
        ]
gtest-all.i(128179): note: see reference to function template instantiation '_OutputIt std::_Fmt_write<_CharT,std::back_insert_iterator<std::string>,_Ty>(_OutputIt,const _Integral,const std::_Basic_format_specs<_CharT> &,std::locale)' being compiled
        with
        [
            _OutputIt=std::back_insert_iterator<std::string>,
            _CharT=char,
            _Ty=int,
            _Integral=int
        ]
gtest-all.i(126088): note: see reference to function template instantiation '_OutputIt std::_Arg_formatter<_OutputIt,_CharT>::operator ()<int>(_Ty)' being compiled
        with
        [
            _OutputIt=std::back_insert_iterator<std::string>,
            _CharT=char,
            _Ty=int
        ]
gtest-all.i(126088): note: see reference to function template instantiation '_OutputIt std::_Arg_formatter<_OutputIt,_CharT>::operator ()<int>(_Ty)' being compiled
        with
        [
            _OutputIt=std::back_insert_iterator<std::string>,
            _CharT=char,
            _Ty=int
        ]
gtest-all.i(128221): note: see reference to function template instantiation '_OutputIt std::visit_format_arg<std::_Arg_formatter<_OutputIt,_CharT>,_Context>(_Visitor &&,std::basic_format_arg<_Context>)' being compiled
        with
        [
            _OutputIt=std::back_insert_iterator<std::string>,
            _CharT=char,
            _Context=std::format_context,
            _Visitor=std::_Arg_formatter<std::back_insert_iterator<std::string>,char>
        ]
gtest-all.i(128203): note: while compiling class template member function 'const _CharT *std::_Format_handler<_OutputIt,_CharT,std::basic_format_context<std::back_insert_iterator<std::string>,_CharT>>::_On_format_specs(const size_t,const _CharT *,const _CharT *)'
        with
        [
            _CharT=char,
            _OutputIt=std::back_insert_iterator<std::string>
        ]
gtest-all.i(126551): note: see reference to function template instantiation 'const _CharT *std::_Format_handler<_OutputIt,_CharT,std::basic_format_context<std::back_insert_iterator<std::string>,_CharT>>::_On_format_specs(const size_t,const _CharT *,const _CharT *)' being compiled
        with
        [
            _CharT=char,
            _OutputIt=std::back_insert_iterator<std::string>
        ]
gtest-all.i(128342): note: see reference to class template instantiation 'std::_Format_handler<_OutputIt,char,std::basic_format_context<std::back_insert_iterator<std::string>,char>>' being compiled
        with
        [
            _OutputIt=std::back_insert_iterator<std::string>
        ]
gtest-all.i(128400): note: see reference to function template instantiation '_OutputIt std::vformat_to<std::back_insert_iterator<std::string>>(_OutputIt,const std::string_view,const std::basic_format_args<std::format_context>)' being compiled
        with
        [
            _OutputIt=std::back_insert_iterator<std::string>
        ]
gtest-all.i(127456): warning C4018: '<=': signed/unsigned mismatch
gtest-all.i(127454): warning C4018: '<=': signed/unsigned mismatch
gtest-all.i(127560): note: see reference to function template instantiation 'bool std::_In_bounds<_CharT,_Integral>(const _Ty)' being compiled
        with
        [
            _CharT=char,
            _Integral=unsigned int,
            _Ty=unsigned int
        ]
gtest-all.i(127669): note: see reference to function template instantiation '_OutputIt std::_Write_integral<_CharT,std::back_insert_iterator<std::string>,_Integral>(_OutputIt,const _Integral,std::_Basic_format_specs<_CharT>,std::locale)' being compiled
        with
        [
            _OutputIt=std::back_insert_iterator<std::string>,
            _CharT=char,
            _Integral=unsigned int
        ]
gtest-all.i(128179): note: see reference to function template instantiation '_OutputIt std::_Fmt_write<_CharT,std::back_insert_iterator<std::string>,_Ty>(_OutputIt,const _Integral,const std::_Basic_format_specs<_CharT> &,std::locale)' being compiled
        with
        [
            _OutputIt=std::back_insert_iterator<std::string>,
            _CharT=char,
            _Ty=unsigned int,
            _Integral=unsigned int
        ]
gtest-all.i(126090): note: see reference to function template instantiation '_OutputIt std::_Arg_formatter<_OutputIt,_CharT>::operator ()<unsigned int>(_Ty)' being compiled
        with
        [
            _OutputIt=std::back_insert_iterator<std::string>,
            _CharT=char,
            _Ty=unsigned int
        ]
gtest-all.i(126090): note: see reference to function template instantiation '_OutputIt std::_Arg_formatter<_OutputIt,_CharT>::operator ()<unsigned int>(_Ty)' being compiled
        with
        [
            _OutputIt=std::back_insert_iterator<std::string>,
            _CharT=char,
            _Ty=unsigned int
        ]

@StephanTLavavej StephanTLavavej added bug Something isn't working format C++20/23 format labels Apr 23, 2021
@StephanTLavavej StephanTLavavej requested a review from a team as a code owner April 23, 2021 01:23
@StephanTLavavej StephanTLavavej merged commit f675d68 into microsoft:main Apr 23, 2021
@StephanTLavavej StephanTLavavej deleted the format_in_range branch April 23, 2021 04:16
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@mnatsuhara mnatsuhara mnatsuhara approved these changes

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