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cfloating-pointieee-754c11standards-compliance

Is there any C compiler which defines both __STDC__ and __STDC_IEC_559__ to 1?

Is there any C compiler(s) which defines both __STDC__ and __STDC_IEC_559__ to 1?

If so, then which one(s)?

Reason of the question: as far as I can test (April 2021), none of the latest versions of popular C compilers (gcc, clang, msvc) define both __STDC__ and __STDC_IEC_559__ to 1. Hence, these compilers may generate executable files, which produce non-IEEE 754 conformant results. However, there is a demand on such C compilers, which actually provide a guarantee / confidence that generated executable files produce IEEE 754 conformant results (under strict floating-point model option).

Solution

  • Yes. It turned out that in gcc and clang definition of __STDC_IEC_559__ depends on the host OS. In case of Windows: __STDC_IEC_559__ is 0. In case of Linux: __STDC_IEC_559__ is 1.

    Here are the options to get both __STDC__ and __STDC_IEC_559__ defined to 1:

    clang -std=c11 -ffp-model=strict
gcc -std=c11 -frounding-math -fsignaling-nans

    UPD20211229: Intel C compiler defines both __STDC__ and __STDC_IEC_559__ to 1:

    icc -std=c11 -fp-model=strict