Check glibc version for a particular gcc compiler

gnu_get_libc_version identifies the runtime version of the GNU C Library.

If what you care about is the compile-time version (that is, the version that provided the headers in /usr/include), you should look at the macros __GLIBC__ and __GLIBC_MINOR__. These expand to positive integers, and will be defined as a side-effect of including any header file provided by the GNU C Library; this means you can include a standard header, and then use #ifdef __GLIBC__ to decide whether you can include a nonstandard header like gnu/libc-version.h.

Expanding the test program from the accepted answer:

#include <stdio.h>
#ifdef __GLIBC__
#include <gnu/libc-version.h>
#endif

int
main(void)
{
#ifdef __GLIBC__
  printf("GNU libc compile-time version: %u.%u\n", __GLIBC__, __GLIBC_MINOR__);
  printf("GNU libc runtime version:      %s\n", gnu_get_libc_version());
  return 0;
#else
  puts("Not the GNU C Library");
  return 1;
#endif
}

When I compile and run this program on the computer I'm typing this answer on (which is a Mac) it prints

Not the GNU C Library

but when compiled and run on a nearby Linux box it prints

GNU libc compile-time version: 2.24
GNU libc runtime version:      2.24

Under normal circumstances, the "runtime" version could be bigger than the "compile-time" version, but never smaller. The major version number is unlikely ever to change again (the last time it changed was the "libc6 transition" in 1997).

If you would prefer a shell 'one-liner' to dump these macros, use:

echo '#include <errno.h>' | gcc -xc - -E -dM | 
    grep -E '^#define __GLIBC(|_MINOR)__ ' | sort

The grep pattern is chosen to match only the two macros that are relevant, because there are dozens of internal macros named __GLIBC_somethingorother that you don't want to have to read through.


Write a test program (name it for example glibc-version.c):

#include <stdio.h>
#include <stdlib.h>
#include <gnu/libc-version.h>

int main(int argc, char *argv[]) {
  printf("GNU libc version: %s\n", gnu_get_libc_version());
  exit(EXIT_SUCCESS);
}

and compile it with the gcc-4.4 compiler: 

gcc-4.4 glibc-version.c -o glibc-version

When you execute ./glibc-version the used glibc version is shown.


Use -print-file-name gcc option:

$ gcc -print-file-name=libc.so
/usr/lib/gcc/x86_64-linux-gnu/9/../../../x86_64-linux-gnu/libc.so

That gives the path. Let's examine the file:

$ file $(gcc -print-file-name=libc.so)
/usr/lib/gcc/x86_64-linux-gnu/9/../../../x86_64-linux-gnu/libc.so: ASCII text

$ cat $(gcc -print-file-name=libc.so)
/* GNU ld script
   Use the shared library, but some functions are only in
   the static library, so try that secondarily.  */
OUTPUT_FORMAT(elf64-x86-64)
GROUP ( /lib/x86_64-linux-gnu/libc.so.6 /usr/lib/x86_64-linux-gnu/libc_nonshared.a  AS_NEEDED ( /lib/x86_64-linux-gnu/ld-linux-x86-64.so.2 ) )

The file is a linker script, which links the libraries in GROUP list.

On ELF platforms /lib/x86_64-linux-gnu/libc.so.6 is a position-independent executable with a dynamic symbol table (like that of a shared library):

$ file /lib/x86_64-linux-gnu/libc.so.6
/lib/x86_64-linux-gnu/libc.so.6: symbolic link to libc-2.31.so

$ file $(readlink -f /lib/x86_64-linux-gnu/libc.so.6)
/usr/lib/x86_64-linux-gnu/libc-2.31.so: ELF 64-bit LSB shared object, x86-64, version 1 (GNU/Linux), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=1878e6b475720c7c51969e69ab2d276fae6d1dee, for GNU/Linux 3.2.0, stripped

$ /lib/x86_64-linux-gnu/libc.so.6
GNU C Library (Ubuntu GLIBC 2.31-0ubuntu9.9) stable release version 2.31.
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.
Compiled by GNU CC version 9.4.0.
libc ABIs: UNIQUE IFUNC ABSOLUTE
For bug reporting instructions, please see:
<https://bugs.launchpad.net/ubuntu/+source/glibc/+bugs>.

even easier

use ldd --version

This should return the glibc version being used i.e.

$ ldd --version

ldd (GNU libc) 2.17
Copyright (C) 2012 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO

...

which is the same result as running my libc library

$ /lib/libc.so.6 


GNU C Library (GNU libc) stable release version 2.17, by Roland McGrath et al.
Copyright (C) 2012 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.

...

Tags:

C

Gcc

Glibc

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