If you statically link, it doesn't matter what version of glibc is on the target machine, because it's not used.

You would think so, but it's not true. I struggled with this for a few days before giving up (after finding articles which stated that this is really going where nobody went before)

> Static linking of glibc is not supported on Red Hat Enterprise Linux.

https://developers.redhat.com/blog/2016/02/17/upgrading-the-...

I don't pretend to know a lot about linking files, but I just checked an old static ffmbc binary I had lying around

  :/tmp$ file ffmbc 
    ffmbc: ELF 64-bit LSB  executable, x86-64, version 1 (SYSV), 
  statically linked, for GNU/Linux 2.6.15, BuildID[sha1]=...., stripped
  :/tmp$ ldd ffmbc 
	not a dynamic executable
 

It runs on the following libc versions:

  ldd (GNU libc) 2.12 (Centos 6.9)
  ldd (Ubuntu EGLIBC 2.19-0ubuntu6.14) 2.19 (ubuntu 14.04)
  ldd (Ubuntu GLIBC 2.23-0ubuntu10) 2.23 (Ubuntu 16.04)

I'm fairly sure it ran on distributions as old as ubuntu 8.04

You're supposed to bundle a fixed version of glibc with your application.