Check glibc version for a particular gcc compiler

Question

I have two gcc compilers installed on my system, one is gcc 4.1.2 (default) and the other is gcc 4.4.4. How can I check the libc version used by

Answer 1

Use -print-file-name gcc option:

$ gcc -print-file-name=libc.so
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../lib64/libc.so

That gives the path. Now:

$ file /usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../lib64/libc.so
/usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../lib64/libc.so: ASCII C program text

$ cat /usr/lib/gcc/x86_64-redhat-linux/4.5.1/../../../../lib64/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 ( /lib64/libc.so.6 /usr/lib64/libc_nonshared.a  AS_NEEDED ( /lib64/ld-linux-x86-64.so.2 ) )

Looks like a linker script. libc is special on Linux in that it can be executed:

$ /lib64/libc.so.6
GNU C Library stable release version 2.13, by Roland McGrath et al.
Copyright (C) 2011 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 4.5.1 20100924 (Red Hat 4.5.1-4).
Compiled on a Linux 2.6.35 system on 2011-08-05.
Available extensions:
    Support for some architectures added on, not maintained in glibc core.
    The C stubs add-on version 2.1.2.
    crypt add-on version 2.1 by Michael Glad and others
    GNU Libidn by Simon Josefsson
    Native POSIX Threads Library by Ulrich Drepper et al
    BIND-8.2.3-T5B
    RT using linux kernel aio
libc ABIs: UNIQUE IFUNC
For bug reporting instructions, please see:
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