Newer glibc needs __GLIBC_FLT_EVAL_METHOD to be defined, but it is not.

[JonPsson]

Starting with 32b73bc "Add support for floating-point option ffp-eval-method and for pragma clang fp eval_method", clang fails during compiliation with "# error "Unknown __GLIBC_FLT_EVAL_METHOD"".

This happens on SystemZ with glibc 2.32, but not 2.30.

GCC defines these macros like:

#define FLT_EVAL_METHOD 0
#define FLT_EVAL_METHOD_TS_18661_3 0

and I suppose that's what is missing in Clang.

It see in llvm sources:

libcxx/include/float.h:#define FLT_EVAL_METHOD FLT_EVAL_METHOD

, but no definition of FLT_EVAL_METHOD anywhere...?

[llvmbot]

@llvm/issue-subscribers-clang-driver

[jdoerfert]

This happens for X86 as well, just include cmath and add -save-temps: https://godbolt.org/z/W1fWcx5sT

[zahiraam]

Yes, Working on a fix. Thanks.

[zahiraam]

This happens for X86 as well, just include cmath and add -save-temps: https://godbolt.org/z/W1fWcx5sT

I looked at the pre-processed output of #include and I don't see any reference of FLT_EVAL_METHOD?

[zahiraam]

I was able to reproduce the issue and this fix https://reviews.llvm.org/D120155 (edited with the review comments) has been added to the bigger patch https://reviews.llvm.org/D109239