gcc: Reduce libc required version

Question

I am trying to run a newly compiled binary on some oldish 32bits RedHat distribution.
The binary is compiled C (not++) on a CentOS 32bits VM running libc v2.12.

Red

Answer 1

I already had the same problem, trying to compile a little tool (I wrote) for an old machine for which I had not compiler. I compiled it on an up to date machine, and the binary required at least GLIBC 2.14 in order to run.

By making a dump of the binary (with xxd), I found this :

....
5f64 736f 5f68 616e 646c 6500 6d65 6d63  _dso_handle.memc
7079 4040 474c 4942 435f 322e 3134 005f  py@@GLIBC_2.14._
....

So I replaced the memcpy calls in my code by a call to an home-made memcpy, and the dependency with the glibc 2.14 magically disappeared.

I'm sorry I can't really explain why it worked, or I can't explain why it didn't work before the modification.

Hope it helped !