I compile with glibc 2.17 and my programs run on all gnu systems.
Have a look at the nightmare recipes for libc. On the other hand they do provide the basics of how to ship a custom libc loader across heterogeneous machines but it gets complicated fast and not something any non specialist can do in an hour.
In my experience anybody saying to compile statically does not know about the libc limitations. When they find them they hand wave, I smile and say be my guest.
By the way 2.17 is an appropriate version to target. RHEL6 much? :D
Of course, new code may actually need features from newer libc, and often you won't be able to frankenstein your way out of it with no-op plug functions and copypasting successfully.
There's also a random page on the internet with a barebones cross-distribution compatibility guide:
https://gist.github.com/wagenet/35adca1a032cec2999d47b6c40aa...
In general, “community support” shrinks to “ride on what Red Hat provides”.
We used https://crosstool-ng.github.io/docs/ to create a cross-compilation toolchain that runs on modern debian, but produces executables that only need glibc 2.17. The only downside is that you no longer can simply apt-get a library you need -- all dependencies shipped along with your application also need to be built with this cross-compiler.
God, I hate glibc so much. It’s an absolutely terrible design from the 80s. It can and should be trivial to target any arbitrary version of glibc. The way Linux performs linking is so bad and so much worse than Windows. (Headers + thin import lib. Linking expecting a full and complete so is stupid and bad.)
Zig solved this problem. It can trivially target any version of glibc and cross-compile. It’d be nice if the Linux community demanded this level of functionality from their toolchains. Alas. https://andrewkelley.me/post/zig-cc-powerful-drop-in-replace...
What Zig does is goes way way way out of it's way to compile import libs which contains all of the exported functions but the implementations are empty.
So you aren't wrong. But the point is that the monumentally large Linux ecosystem does not work that way. Which is a real shame.
The actual dependency is 2.14, when a faster memcpy was added, 2.17 is just whatever I happened to have around back when I compiled my stuff, I just didn't change anything since then, bits don't rot.