[flang-rt] Added FLANG_RT_QUADMATH_INCLUDE_DIR option.

[vzakhari]

It allows specifying path to quadmath.h directory,
which is needed when building flang-rt with
FLANG_RUNTIME_F128_MATH_LIB=libquadmath using clang.

[Meinersbur]

Why not just -DCMAKE_CXX_FLAGS=-I/usr//lib/gcc/x86_64-linux-gnu/13/include? No additional configuration complexity needed.

Clang is already searching for gcc installations, just doesn't add its include dir to the default header search path.

[vzakhari]

Why not just -DCMAKE_CXX_FLAGS=-I/usr//lib/gcc/x86_64-linux-gnu/13/include? No additional configuration complexity needed.

Clang is already searching for gcc installations, just doesn't add its include dir to the default header search path.

check_include_file does not rely on CMAKE_C/CXX_FLAGS for compiling the sample code.

[vzakhari]

Clang is already searching for gcc installations, just doesn't add its include dir to the default header search path.

I do not think it is possible to use both clang's and gcc's include paths in the same clang compilation. If you try you would get lots of errors due to conflicting header files.

[Meinersbur]

check_include_file does not rely on CMAKE_C/CXX_FLAGS for compiling the sample code.

From the documention:

CMAKE_REQUIRED_FLAGS
String of additional flags to pass to the compiler. The string must be space-delimited--a ;-list will not work. The contents of CMAKE_<LANG>_FLAGS and its associated configuration-specific variable are automatically added to the compiler command before the contents of CMAKE_REQUIRED_FLAGS.

If the issue is that the parameter is not forwarded to the runtimes build, that's what -DRUNTIMES_CMAKE_ARGS="-DCMAKE_CXX_FLANGS=..." is for.

[Meinersbur]

I do not think it is possible to use both clang's and gcc's include paths in the same clang compilation. If you try you would get lots of errors due to conflicting header files.

Isn't this exactly what include_directories(${FLANG_RT_QUADMATH_INCLUDE_DIR}) does? Or do you expect users to copy GCC's quadmath.h into another directory?

Better solution here: #130411. No additional configuration input from the user required.

[vzakhari]

If the issue is that the parameter is not forwarded to the runtimes build, that's what -DRUNTIMES_CMAKE_ARGS="-DCMAKE_CXX_FLANGS=..." is for.

I tried exactly -DRUNTIMES_CMAKE_ARGS="-DCMAKE_CXX_FLANGS=..." method, but it did not work for some reason. Let me try it again.

[Meinersbur]

Sorry, there was a typo: -DRUNTIMES_CMAKE_ARGS="-DCMAKE_CXX_FLAGS=-I/usr/lib/gcc/x86_64-linux-gnu/13/include" (FLAGS instead of FLANGS)

[vzakhari]

Sorry, there was a typo: -DRUNTIMES_CMAKE_ARGS="-DCMAKE_CXX_FLAGS=-I/usr/lib/gcc/x86_64-linux-gnu/13/include" (FLAGS instead of FLANGS)

No problem :) I did try it (without the typo) before I posted this PR, that is why I went with the extra var. I could have made a different typo though.

[vzakhari]

Isn't this exactly what include_directories(${FLANG_RT_QUADMATH_INCLUDE_DIR}) does? Or do you expect users to copy GCC's quadmath.h into another directory?

Better solution here: #130411. No additional configuration input from the user required.

I like your solution better. Thanks! Let me try it.

[vzakhari]

Closing this in favor of #130411.