Article doesn't really address the question of whether you can ALWAYS trust inlining. I can tell you from experience the answer is no. We have some libraries at work that implement generic evaluation of functions over pages of objects, as in the context of a database. The authors did this in the "proper" C++ way, which involved a lot of generics and templates. They also sprinkled inline directives all over the place, apparently without ever actually benchmarking each individual case.

What it ended up with is a bunch of absolutely enormous modules, each generating tens of megabytes of mostly identical code, but with the leaf functions in each case handling floats, ints, strings, etc.

Removing some of these inline directives probably would not impact the code at all, since most of the inlined code was cold. But it would likely benefit build performance quite a bit. It might even improve runtime performance by putting less pressure on the cache.

This is probably not a surprise, but inlining is best for hot leaf code. Cold code should probably not be inlined unless it is used exactly once.