Varying filesize of libstdc++.so.6.0.19

[Mohan Ganesalingam <mohan0 at gmail dot com>]

Hi,

I'm trying to understand when a library can be built against libstdc++ on
one distro and then used on another distro. While looking into this, I
found that the size of  libstdc++.so can vary even when you are looking at
the same so version (6.0.19) on different versions of the same OS:

centos:7.0.1406
-rwxr-xr-x 1 root root 991744 Jun 10  2014 ./usr/lib64/libstdc++.so.6.0.19

centos:7.1.1503
-rwxr-xr-x 1 root root 991744 Mar  5  2015 ./usr/lib64/libstdc++.so.6.0.19

centos:7.2.1511
-rwxr-xr-x 1 root root 995840 Nov 19  2015 ./usr/lib64/libstdc++.so.6.0.19

centos:7.3.1611
-rwxr-xr-x 1 root root 999944 Nov  4  2016 ./usr/lib64/libstdc++.so.6.0.19

centos:7.4.1708
-rwxr-xr-x 1 root root 995840 Aug  1  2017 ./usr/lib64/libstdc++.so.6.0.19

Would anyone be able to explain how this might be happening? If the source
code is the same and the ABI is the same, I would have thought that you
would get the same output.  Is it possible that some of these versions are
more optimised than others because they were compiled with different
versions of gcc?

Thanks very much!  I'm aware this is a pretty basic question, but I'm
finding it hard to know where to start on all of this…

Best wishes,
Mohan