Clang 18+ /fp:fast emits -Wnan-infinity-disabled in VSO_0000000_vector_algorithms_floats

[CaseyCarter]

All 8 clang-cl /fp:fast configs have the same issue. For example:

Error log for clang-cl /fp:fast /MT without /D_USE_STD_VECTOR_ALGORITHMS=0

FAIL: std :: tests/VSO_0000000_vector_algorithms_floats:16 (6 of 24)
******************** TEST 'std :: tests/VSO_0000000_vector_algorithms_floats:16' FAILED ********************
Build setup steps:
Build steps:
Build step failed unexpectedly.
Command: "c:\Program Files\LLVM19\bin\clang-cl.EXE" "C:\STL\tests\std\tests\VSO_0000000_vector_algorithms_floats\test.cpp" "-IC:\STL\out\x64\out\inc" "-IC:\STL\llvm-project\libcxx\test\support" "-IC:\STL\tests\std\include" "/nologo" "/Od" "/W4" "/w14061" "/w14242" "/w14265" "/w14582" "/w14583" "/w14587" "/w14588" "/w14749" "/w14841" "/w14842" "/w15038" "/w15214" "/w15215" "/w15216" "/w15217" "/w15262" "/sdl" "/WX" "/D_ENABLE_STL_INTERNAL_CHECK" "/bigobj" "/FIforce_include.hpp" "/w14365" "/w14668" "/w15267" "/D_ENFORCE_FACET_SPECIALIZATIONS=1" "/D_STL_CALL_ABORT_INSTEAD_OF_INVALID_PARAMETER" "-fno-ms-compatibility" "-fno-delayed-template-parsing" "-Wno-unqualified-std-cast-call" "/EHsc" "/MT" "/std:c++20" "/permissive-" "/w14640" "/Zc:threadSafeInit-" "--start-no-unused-arguments" "/fp:fast" "-m64" "-FeC:\STL\out\x64\tests\std\tests\VSO_0000000_vector_algorithms_floats\Output\16\VSO_0000000_vector_algorithms_floats.exe" "-link" "-LIBPATH:C:\STL\out\x64\out\lib\amd64" "-LIBPATH:C:\Program Files\Microsoft Visual Studio\2022\Preview\VC\Tools\MSVC\14.42.34226\lib\x64" "/MANIFEST:EMBED"
Exit Code: 1 (0x1)
Standard Error:
--
In file included from C:\STL\tests\std\tests\VSO_0000000_vector_algorithms_floats\test.cpp:5:
C:\STL\out\x64\out\inc\limits(883,16): error: use of NaN is undefined behavior due to the currently enabled floating-point options [-Werror,-Wnan-infinity-disabled]
  883 |         return __builtin_nanf("0");
      |                ^~~~~~~~~~~~~~~~~~~
In file included from C:\STL\tests\std\tests\VSO_0000000_vector_algorithms_floats\test.cpp:6:
In file included from C:\STL\out\x64\out\inc\random:13:
C:\STL\out\x64\out\inc\cmath(671,1): error: use of infinity is undefined behavior due to the currently enabled floating-point options [-Werror,-Wnan-infinity-disabled]
  671 | _CLANG_BUILTIN1(isfinite)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(662,5): note: expanded from macro '_CLANG_BUILTIN1'
  662 |     _CLANG_BUILTIN1_ARG(NAME, float)  \
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(605,16): note: expanded from macro '_CLANG_BUILTIN1_ARG'
  605 |         return __builtin_##NAME(_Xx);                                                            \
      |                ^~~~~~~~~~~~~~~~~~~~~
(196,1): note: expanded from here
  196 | __builtin_isfinite
      | ^
In file included from C:\STL\tests\std\tests\VSO_0000000_vector_algorithms_floats\test.cpp:6:
In file included from C:\STL\out\x64\out\inc\random:13:
C:\STL\out\x64\out\inc\cmath(671,1): error: use of infinity is undefined behavior due to the currently enabled floating-point options [-Werror,-Wnan-infinity-disabled]
  671 | _CLANG_BUILTIN1(isfinite)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(663,5): note: expanded from macro '_CLANG_BUILTIN1'
  663 |     _CLANG_BUILTIN1_ARG(NAME, double) \
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(605,16): note: expanded from macro '_CLANG_BUILTIN1_ARG'
  605 |         return __builtin_##NAME(_Xx);                                                            \
      |                ^~~~~~~~~~~~~~~~~~~~~
(199,1): note: expanded from here
  199 | __builtin_isfinite
      | ^
In file included from C:\STL\tests\std\tests\VSO_0000000_vector_algorithms_floats\test.cpp:6:
In file included from C:\STL\out\x64\out\inc\random:13:
C:\STL\out\x64\out\inc\cmath(671,1): error: use of infinity is undefined behavior due to the currently enabled floating-point options [-Werror,-Wnan-infinity-disabled]
  671 | _CLANG_BUILTIN1(isfinite)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(664,5): note: expanded from macro '_CLANG_BUILTIN1'
  664 |     _CLANG_BUILTIN1_ARG(NAME, long double)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(605,16): note: expanded from macro '_CLANG_BUILTIN1_ARG'
  605 |         return __builtin_##NAME(_Xx);                                                            \
      |                ^~~~~~~~~~~~~~~~~~~~~
(202,1): note: expanded from here
  202 | __builtin_isfinite
      | ^
In file included from C:\STL\tests\std\tests\VSO_0000000_vector_algorithms_floats\test.cpp:6:
In file included from C:\STL\out\x64\out\inc\random:13:
C:\STL\out\x64\out\inc\cmath(672,1): error: use of infinity is undefined behavior due to the currently enabled floating-point options [-Werror,-Wnan-infinity-disabled]
  672 | _CLANG_BUILTIN1(isinf)
      | ^~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(662,5): note: expanded from macro '_CLANG_BUILTIN1'
  662 |     _CLANG_BUILTIN1_ARG(NAME, float)  \
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(605,16): note: expanded from macro '_CLANG_BUILTIN1_ARG'
  605 |         return __builtin_##NAME(_Xx);                                                            \
      |                ^~~~~~~~~~~~~~~~~~~~~
(205,1): note: expanded from here
  205 | __builtin_isinf
      | ^
In file included from C:\STL\tests\std\tests\VSO_0000000_vector_algorithms_floats\test.cpp:6:
In file included from C:\STL\out\x64\out\inc\random:13:
C:\STL\out\x64\out\inc\cmath(672,1): error: use of infinity is undefined behavior due to the currently enabled floating-point options [-Werror,-Wnan-infinity-disabled]
  672 | _CLANG_BUILTIN1(isinf)
      | ^~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(663,5): note: expanded from macro '_CLANG_BUILTIN1'
  663 |     _CLANG_BUILTIN1_ARG(NAME, double) \
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(605,16): note: expanded from macro '_CLANG_BUILTIN1_ARG'
  605 |         return __builtin_##NAME(_Xx);                                                            \
      |                ^~~~~~~~~~~~~~~~~~~~~
(208,1): note: expanded from here
  208 | __builtin_isinf
      | ^
In file included from C:\STL\tests\std\tests\VSO_0000000_vector_algorithms_floats\test.cpp:6:
In file included from C:\STL\out\x64\out\inc\random:13:
C:\STL\out\x64\out\inc\cmath(672,1): error: use of infinity is undefined behavior due to the currently enabled floating-point options [-Werror,-Wnan-infinity-disabled]
  672 | _CLANG_BUILTIN1(isinf)
      | ^~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(664,5): note: expanded from macro '_CLANG_BUILTIN1'
  664 |     _CLANG_BUILTIN1_ARG(NAME, long double)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(605,16): note: expanded from macro '_CLANG_BUILTIN1_ARG'
  605 |         return __builtin_##NAME(_Xx);                                                            \
      |                ^~~~~~~~~~~~~~~~~~~~~
(211,1): note: expanded from here
  211 | __builtin_isinf
      | ^
In file included from C:\STL\tests\std\tests\VSO_0000000_vector_algorithms_floats\test.cpp:6:
In file included from C:\STL\out\x64\out\inc\random:13:
C:\STL\out\x64\out\inc\cmath(673,1): error: use of NaN is undefined behavior due to the currently enabled floating-point options [-Werror,-Wnan-infinity-disabled]
  673 | _CLANG_BUILTIN1(isnan)
      | ^~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(662,5): note: expanded from macro '_CLANG_BUILTIN1'
  662 |     _CLANG_BUILTIN1_ARG(NAME, float)  \
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(605,16): note: expanded from macro '_CLANG_BUILTIN1_ARG'
  605 |         return __builtin_##NAME(_Xx);                                                            \
      |                ^~~~~~~~~~~~~~~~~~~~~
(214,1): note: expanded from here
  214 | __builtin_isnan
      | ^
In file included from C:\STL\tests\std\tests\VSO_0000000_vector_algorithms_floats\test.cpp:6:
In file included from C:\STL\out\x64\out\inc\random:13:
C:\STL\out\x64\out\inc\cmath(673,1): error: use of NaN is undefined behavior due to the currently enabled floating-point options [-Werror,-Wnan-infinity-disabled]
  673 | _CLANG_BUILTIN1(isnan)
      | ^~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(663,5): note: expanded from macro '_CLANG_BUILTIN1'
  663 |     _CLANG_BUILTIN1_ARG(NAME, double) \
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(605,16): note: expanded from macro '_CLANG_BUILTIN1_ARG'
  605 |         return __builtin_##NAME(_Xx);                                                            \
      |                ^~~~~~~~~~~~~~~~~~~~~
(217,1): note: expanded from here
  217 | __builtin_isnan
      | ^
In file included from C:\STL\tests\std\tests\VSO_0000000_vector_algorithms_floats\test.cpp:6:
In file included from C:\STL\out\x64\out\inc\random:13:
C:\STL\out\x64\out\inc\cmath(673,1): error: use of NaN is undefined behavior due to the currently enabled floating-point options [-Werror,-Wnan-infinity-disabled]
  673 | _CLANG_BUILTIN1(isnan)
      | ^~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(664,5): note: expanded from macro '_CLANG_BUILTIN1'
  664 |     _CLANG_BUILTIN1_ARG(NAME, long double)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(605,16): note: expanded from macro '_CLANG_BUILTIN1_ARG'
  605 |         return __builtin_##NAME(_Xx);                                                            \
      |                ^~~~~~~~~~~~~~~~~~~~~
(220,1): note: expanded from here
  220 | __builtin_isnan
      | ^
In file included from C:\STL\tests\std\tests\VSO_0000000_vector_algorithms_floats\test.cpp:6:
In file included from C:\STL\out\x64\out\inc\random:13:
C:\STL\out\x64\out\inc\cmath(681,1): error: use of NaN is undefined behavior due to the currently enabled floating-point options [-Werror,-Wnan-infinity-disabled]
  681 | _CLANG_BUILTIN2(isunordered)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(667,5): note: expanded from macro '_CLANG_BUILTIN2'
  667 |     _CLANG_BUILTIN2_ARG(NAME, float)  \
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(611,16): note: expanded from macro '_CLANG_BUILTIN2_ARG'
  611 |         return __builtin_##NAME(_Xx, _Yx);                                                               \
      |                ^~~~~~~~~~~~~~~~~~~~~~~~~~
(293,1): note: expanded from here
  293 | __builtin_isunordered
      | ^
In file included from C:\STL\tests\std\tests\VSO_0000000_vector_algorithms_floats\test.cpp:6:
In file included from C:\STL\out\x64\out\inc\random:13:
C:\STL\out\x64\out\inc\cmath(681,1): error: use of NaN is undefined behavior due to the currently enabled floating-point options [-Werror,-Wnan-infinity-disabled]
  681 | _CLANG_BUILTIN2(isunordered)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(668,5): note: expanded from macro '_CLANG_BUILTIN2'
  668 |     _CLANG_BUILTIN2_ARG(NAME, double) \
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(611,16): note: expanded from macro '_CLANG_BUILTIN2_ARG'
  611 |         return __builtin_##NAME(_Xx, _Yx);                                                               \
      |                ^~~~~~~~~~~~~~~~~~~~~~~~~~
(297,1): note: expanded from here
  297 | __builtin_isunordered
      | ^
In file included from C:\STL\tests\std\tests\VSO_0000000_vector_algorithms_floats\test.cpp:6:
In file included from C:\STL\out\x64\out\inc\random:13:
C:\STL\out\x64\out\inc\cmath(681,1): error: use of NaN is undefined behavior due to the currently enabled floating-point options [-Werror,-Wnan-infinity-disabled]
  681 | _CLANG_BUILTIN2(isunordered)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(669,5): note: expanded from macro '_CLANG_BUILTIN2'
  669 |     _CLANG_BUILTIN2_ARG(NAME, long double)
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(611,16): note: expanded from macro '_CLANG_BUILTIN2_ARG'
  611 |         return __builtin_##NAME(_Xx, _Yx);                                                               \
      |                ^~~~~~~~~~~~~~~~~~~~~~~~~~
(301,1): note: expanded from here
  301 | __builtin_isunordered
      | ^
In file included from C:\STL\tests\std\tests\VSO_0000000_vector_algorithms_floats\test.cpp:6:
In file included from C:\STL\out\x64\out\inc\random:13:
C:\STL\out\x64\out\inc\cmath(688,1): error: use of NaN is undefined behavior due to the currently enabled floating-point options [-Werror,-Wnan-infinity-disabled]
  688 | _CLANG_BUILTIN2_TEMPLATED(isunordered)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(641,5): note: expanded from macro '_CLANG_BUILTIN2_TEMPLATED'
  641 |     _CLANG_BUILTIN2_ARG_TEMPLATED(NAME, float)              \
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(617,16): note: expanded from macro '_CLANG_BUILTIN2_ARG_TEMPLATED'
  617 |         return __builtin_##NAME(static_cast(_Xx), static_cast(_Yx));                     \
      |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
(81,1): note: expanded from here
   81 | __builtin_isunordered
      | ^
In file included from C:\STL\tests\std\tests\VSO_0000000_vector_algorithms_floats\test.cpp:6:
In file included from C:\STL\out\x64\out\inc\random:13:
C:\STL\out\x64\out\inc\cmath(688,1): error: use of NaN is undefined behavior due to the currently enabled floating-point options [-Werror,-Wnan-infinity-disabled]
  688 | _CLANG_BUILTIN2_TEMPLATED(isunordered)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(642,5): note: expanded from macro '_CLANG_BUILTIN2_TEMPLATED'
  642 |     _CLANG_BUILTIN2_ARG_TEMPLATED(NAME, double)             \
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(617,16): note: expanded from macro '_CLANG_BUILTIN2_ARG_TEMPLATED'
  617 |         return __builtin_##NAME(static_cast(_Xx), static_cast(_Yx));                     \
      |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
(85,1): note: expanded from here
   85 | __builtin_isunordered
      | ^
In file included from C:\STL\tests\std\tests\VSO_0000000_vector_algorithms_floats\test.cpp:6:
In file included from C:\STL\out\x64\out\inc\random:13:
C:\STL\out\x64\out\inc\cmath(688,1): error: use of NaN is undefined behavior due to the currently enabled floating-point options [-Werror,-Wnan-infinity-disabled]
  688 | _CLANG_BUILTIN2_TEMPLATED(isunordered)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(643,5): note: expanded from macro '_CLANG_BUILTIN2_TEMPLATED'
  643 |     _CLANG_BUILTIN2_ARG_TEMPLATED(NAME, long double)        \
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(617,16): note: expanded from macro '_CLANG_BUILTIN2_ARG_TEMPLATED'
  617 |         return __builtin_##NAME(static_cast(_Xx), static_cast(_Yx));                     \
      |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
(89,1): note: expanded from here
   89 | __builtin_isunordered
      | ^
In file included from C:\STL\tests\std\tests\VSO_0000000_vector_algorithms_floats\test.cpp:6:
In file included from C:\STL\out\x64\out\inc\random:13:
C:\STL\out\x64\out\inc\cmath(688,1): error: use of NaN is undefined behavior due to the currently enabled floating-point options [-Werror,-Wnan-infinity-disabled]
  688 | _CLANG_BUILTIN2_TEMPLATED(isunordered)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(644,5): note: expanded from macro '_CLANG_BUILTIN2_TEMPLATED'
  644 |     _CLANG_BUILTIN2_ARG_TEMPLATED(NAME, signed char)        \
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(617,16): note: expanded from macro '_CLANG_BUILTIN2_ARG_TEMPLATED'
  617 |         return __builtin_##NAME(static_cast(_Xx), static_cast(_Yx));                     \
      |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
(93,1): note: expanded from here
   93 | __builtin_isunordered
      | ^
In file included from C:\STL\tests\std\tests\VSO_0000000_vector_algorithms_floats\test.cpp:6:
In file included from C:\STL\out\x64\out\inc\random:13:
C:\STL\out\x64\out\inc\cmath(688,1): error: use of NaN is undefined behavior due to the currently enabled floating-point options [-Werror,-Wnan-infinity-disabled]
  688 | _CLANG_BUILTIN2_TEMPLATED(isunordered)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(645,5): note: expanded from macro '_CLANG_BUILTIN2_TEMPLATED'
  645 |     _CLANG_BUILTIN2_ARG_TEMPLATED(NAME, short)              \
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(617,16): note: expanded from macro '_CLANG_BUILTIN2_ARG_TEMPLATED'
  617 |         return __builtin_##NAME(static_cast(_Xx), static_cast(_Yx));                     \
      |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
(97,1): note: expanded from here
   97 | __builtin_isunordered
      | ^
In file included from C:\STL\tests\std\tests\VSO_0000000_vector_algorithms_floats\test.cpp:6:
In file included from C:\STL\out\x64\out\inc\random:13:
C:\STL\out\x64\out\inc\cmath(688,1): error: use of NaN is undefined behavior due to the currently enabled floating-point options [-Werror,-Wnan-infinity-disabled]
  688 | _CLANG_BUILTIN2_TEMPLATED(isunordered)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(646,5): note: expanded from macro '_CLANG_BUILTIN2_TEMPLATED'
  646 |     _CLANG_BUILTIN2_ARG_TEMPLATED(NAME, int)                \
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\STL\out\x64\out\inc\cmath(617,16): note: expanded from macro '_CLANG_BUILTIN2_ARG_TEMPLATED'
  617 |         return __builtin_##NAME(static_cast(_Xx), static_cast(_Yx));                     \
      |                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
(101,1): note: expanded from here
  101 | __builtin_isunordered
      | ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
20 errors generated.
--

#4932 will silence these warnings for the time being.

[AlexGuteniev]

I don't know what you would do about it other than suppression.
/fp:fast is indeed asking for UB for NANs.

[CaseyCarter]

I don't know what you would do about it other than suppression. /fp:fast is indeed asking for UB for NANs.

Ideally, we don't test undefined behavior. It tends to be unreliable. That could mean adding a macro to the /fp:fast configs that tells the tests to avoid problematic code. Or it could mean suppression, or it could mean not running those tests with /fp:fast.

[AlexGuteniev]

I see.

The whole point of separating VSO_0000000_vector_algorithms_floats from VSO_0000000_vector_algorithms was testing the cursed floating modes with the same exhaustive coverage as the standard /fp:precise mode.

Out of the cursed modes, /fp:fast is the main goal for testing, as it changes the control flow for the algorithm in question.

We can possibly drop infinities from /fp:fast coverage, that is, remove these elements:

STL/tests/std/tests/VSO_0000000_vector_algorithms_floats/test.cpp

Lines 33 to 34 in c7c5ca7

	input_of_input[0] = -numeric_limits<T>::infinity();
	input_of_input[1] = +numeric_limits<T>::infinity();

As for NANs. the test doesn't even try them in the standard /fp:precise mode. We've concluded that we don't support NANs in the sorting algorithms.

But most of these warnings (actually all quoted in the description) originate from <cmath> and <limits> headers.
Need to suppress them in these headers!

[StephanTLavavej]

After one minute of my not-especially-clueful attempting during the weekly maintainer meeting, we weren't able to repro warnings from <limits> with a from-scratch source file. We should extract a minimal repro to understand exactly what about this test is continuing to emit Clang warnings. As usual, if merely including the header and doing not-risky things (like mentioning numeric_limits<double>::stuff() but not specifically inf/nan directly) emits a warning, then we should suppress it in the STL headers, but not if the user is asking us to do risky things on their behalf.