Compiler warning [-Wfloat-equal]

[abdes]

#2848 only partially solved the problem:

[ 33%] Building CXX object test/CMakeFiles/format-test.dir/format-test.cc.o
In file included from /home/xxx/projects/fmt/test/format-test.cc:13:
/home/xxx/projects/fmt/include/fmt/format.h: In instantiation of ‘constexpr bool fmt::v8::detail::isfinite(T) [with T = __float128; typename std::enable_if<std::is_same<T, __float128>::value, int>::type <anonymous> = 0]’:
/home/xxx/projects/fmt/test/format-test.cc:80:3:   required from ‘void check_isfinite() [with Float = __float128]’
/home/xxx/projects/fmt/test/format-test.cc:95:40:   required from here
/home/xxx/projects/fmt/include/fmt/format.h:2308:24: warning: comparing floating-point with ‘==’ or ‘!=’ is unsafe [-Wfloat-equal]
 2308 |   return value - value == 0;  // std::isfinite doesn't support __float128.
      |          ~~~~~~~~~~~~~~^~~~

Additionally, not in the API, but in a test file:

[ 83%] Building CXX object test/CMakeFiles/xchar-test.dir/xchar-test.cc.o
/home/xxx/projects/fmt/test/xchar-test.cc: In member function ‘typename FormatContext::iterator fmt::v8::formatter<std::complex<double>, charT>::format(const std::complex<double>&, FormatContext&)’:
/home/xxx/projects/fmt/test/xchar-test.cc:483:31: warning: comparing floating-point with ‘==’ or ‘!=’ is unsafe [-Wfloat-equal]
  483 |                      c.real() != 0 ? fmt::format("({}+{}i)", real, imag)
      |                      ~~~~~~~~~^~~~
/home/xxx/projects/fmt/test/xchar-test.cc: In instantiation of ‘typename FormatContext::iterator fmt::v8::formatter<std::complex<double>, charT>::format(const std::complex<double>&, FormatContext&) [with FormatContext = fmt::v8::basic_format_context<fmt::v8::appender, char>; charT = char; typename FormatContext::iterator = fmt::v8::appender]’:
/home/xxx/projects/fmt/include/fmt/core.h:1266:28:   required from ‘static void fmt::v8::detail::value<Context>::format_custom_arg(void*, typename Context::parse_context_type&, Context&) [with T = std::complex<double>; Formatter = fmt::v8::formatter<std::complex<double>, char, void>; Context = fmt::v8::basic_format_context<fmt::v8::appender, char>; typename Context::parse_context_type = fmt::v8::basic_format_parse_context<char>]’
/home/xxx/projects/fmt/include/fmt/core.h:1245:19:   required from ‘fmt::v8::detail::value<Context>::value(T&) [with T = const std::complex<double>; Context = fmt::v8::basic_format_context<fmt::v8::appender, char>]’
/home/xxx/projects/fmt/include/fmt/core.h:1727:14:   required from ‘fmt::v8::detail::value<Context> fmt::v8::detail::make_value(T&&) [with Context = fmt::v8::basic_format_context<fmt::v8::appender, char>; T = std::complex<double>&]’
/home/xxx/projects/fmt/include/fmt/core.h:1744:29:   required from ‘fmt::v8::detail::value<Context> fmt::v8::detail::make_arg(T&&) [with bool IS_PACKED = true; Context = fmt::v8::basic_format_context<fmt::v8::appender, char>; fmt::v8::detail::type <anonymous> = fmt::v8::detail::type::custom_type; T = std::complex<double>&; typename std::enable_if<IS_PACKED, int>::type <anonymous> = 0]’
/home/xxx/projects/fmt/include/fmt/core.h:1868:77:   required from ‘fmt::v8::format_arg_store<Context, Args>::format_arg_store(T&& ...) [with T = {std::complex<double>&}; Context = fmt::v8::basic_format_context<fmt::v8::appender, char>; Args = {std::complex<double>}]’
/home/xxx/projects/fmt/include/fmt/core.h:1885:38:   required from ‘constexpr fmt::v8::format_arg_store<Context, typename std::remove_cv<typename std::remove_reference<Args>::type>::type ...> fmt::v8::make_format_args(Args&& ...) [with Context = fmt::v8::basic_format_context<fmt::v8::appender, char>; Args = {std::complex<double>&}]’
/home/xxx/projects/fmt/include/fmt/core.h:3167:44:   required from ‘std::string fmt::v8::format(fmt::v8::format_string<T ...>, T&& ...) [with T = {std::complex<double>}; std::string = std::__cxx11::basic_string<char>; fmt::v8::format_string<T ...> = fmt::v8::basic_format_string<char, std::complex<double> >]’
/home/xxx/projects/fmt/test/xchar-test.cc:490:30:   required from here
/home/xxx/projects/fmt/test/xchar-test.cc:483:31: warning: comparing floating-point with ‘==’ or ‘!=’ is unsafe [-Wfloat-equal]

[abdes]

To reproduce:

mkdir _build
cd _build
cmake -DCMAKE_CXX_FLAGS="-Wfloat-equal" ..
cmake ..

Use gcc or clang.

[vitaut]

In the future please reopen the original issue.