-Ofast not compatible with JUCE

[zsliu98]

Hi! When compiling the code with a newer Clang version, I got the following warnings (I use Clang on Windows, but it should be the same):

D:\a\ZLTest\ZLTest\JUCE\modules\juce_core\text/juce_CharacterFunctions.h(225,30): warning: use of infinity is undefined behavior due to the currently enabled floating-point options [-Wnan-infinity-disabled]
  225 |         constexpr auto inf = std::numeric_limits<double>::infinity();
      |                              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
D:\a\ZLTest\ZLTest\JUCE\modules\juce_core\text/juce_CharacterFunctions.h(423,16): note: in instantiation of function template specialization 'juce::CharacterFunctions::readDoubleValue<juce::CharPointer_UTF32>' requested here
  423 |         return readDoubleValue (text);
      |                ^
D:\a\ZLTest\ZLTest\JUCE\modules\juce_core\text/juce_CharPointer_UTF32.h(349,78): note: in instantiation of function template specialization 'juce::CharacterFunctions::getDoubleValue<juce::CharPointer_UTF32>' requested here
  349 |     double getDoubleValue() const noexcept      { return CharacterFunctions::getDoubleValue (*this); }
      | 

And then I came across the following post:

https://forum.juce.com/t/windows-clangcl-build-warnings-in-8-0-3/64240

What do you think? It seems that the JUCE team is aware of this. Shall we do the modification suggested by the post or choose -O3 instead?

[zsliu98]

Candidate for SharedCodeDefaults.cmake:

if (MSVC)
    # fast math and better simd support in RELEASE
    # https://learn.microsoft.com/en-us/cpp/build/reference/fp-specify-floating-point-behavior?view=msvc-170#fast
    target_compile_options(SharedCode INTERFACE $<$<CONFIG:RELEASE>:/fp:precise>)
else ()
    # See the implications here:
    # https://stackoverflow.com/q/45685487
    target_compile_options(SharedCode INTERFACE $<$<CONFIG:RELEASE>:-O3 -fno-signed-zeros -freciprocal-math -ffp-contract=fast>)
    target_compile_options(SharedCode INTERFACE $<$<CONFIG:RelWithDebInfo>:-O3 -fno-signed-zeros -freciprocal-math -ffp-contract=fast>)
endif ()