[mgaunard]

Different parts of the build seeing inconsistent definitions of the same name is a clear consequence of building things piecemeal rather than as a single project -- which is precisely the problem I described higher up in this thread.

Things being built piecemeal also likely won't be using LTO (even if fat LTO allows this, no static library packages in a distro are built with it).

[uecker]

Not sure what you are trying to say. Inconsistent definitions is a consequence of being able to build things separately, which is a major feature of C and C++, although in C++ it does not work well anymore. The reason to not build things piecemeal is often that LTO is more expensive. But occasionally running this will catch violations. When libraries get split up, the interface is defined via headers and there is little risk to get an inconsistency. So really do not think there is a major problem in C.