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I need to use the C standard to compile with my POSIX implementation. I downloaded the precompiled lib of gcc-11.2, but after unzipping, I am facing libgcc.a and libc.a libraries.

I tried to compile with libc.a, but <stddef.h> is missing. I compiled with both libraries, and it solved the inclusion issue. But a new issue has arisen: the function clock_gettime() isn't being referenced. This function is defined by POSIX (Real Time) as an extension of time.h. I need this file and function for my implementation. I checked with dumpobj on libc.a and libgcc.a, but the function is not present. So, it seems that libc.a has been compiled without the function. A solution can be to compile the GCC sources with the -D_POSIX_TIMERS flag (clock_gettime is defined if _POSIX_TIMERS exists) ?

I don't understand why there are libgcc.a and libc.a instead of one library, what is the difference between these libraries ? And is it possible to use a POSIX function defined in the GCC library without including all the other POSIX features to prevent conflicts with my POSIX implementation ?

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    Any reason you're not installing gcc from your OS's package repository via yum/dpk/apt? Commented Jun 12, 2024 at 13:57
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    Per the documentation, libgcc is a low-level runtime library, that is used by gcc internals "automatically". While libc is the implementation of C library, that is library functions callable by the "user". Commented Jun 12, 2024 at 14:23
  • Generally, you can't/shouldn't use [purely] the .a version of libc. On linux [at least], you want the shared .so as well. Particularly for clock_gettime because (for optimal performance) it's in the VDSO (code injected into the user program by the kernel). See my answer: __rdtsc/__rdtscp for ARM Mac M1/M2? Commented Jun 12, 2024 at 14:33
  • As a side note, you can't conform to the C standard and POSIX at the same time, pick one, say bye-bye to the other. Commented Jun 12, 2024 at 14:44
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    @Eoa It is not. For example it is a requirement for a conforming C implementation not to implement something that affects the behavior of a "strictly conforming program", such as adding identifiers that may also be used by the application. In plain English, the C standard libraries are not allowed to contain non-standard trash. Whereas POSIX requires that the standard libraries are filled up with with non-standard trash. Commented Jun 13, 2024 at 13:35
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