It still happens today, but nowhere near as badly. I package FoundationDB for my linux distribution, and around GCC 6.x the build broke for version FDB 6.0. Why

It still happens today, but nowhere near as badly. I package FoundationDB for my linux distribution, and around GCC 6.x the build broke for version FDB 6.0. Why? Because the code used 'log' unqualified in their code (for logging), and some rearrangement of the libstdc++ headers to be more correct and caused the 'log' (math function) to come into scope. (The libstdc++ changes were the correct course of action, in my reading.) Of course, FDB also changed their code in the mean time so newer versions 6.1+ didn't hit this, so it was an old regression in an old version from a mishap in the standard library that had been a bug for like, years and years. Tons of regressions like this happen all the time in the GCC/LLVM world. Every time we do a bump of the default C compiler, you can bet it will take 4-8 weeks while regressions -- from "This random thing enabled -Werror, again" to "Someone used a new feature but scoped the #ifdef wrong" to "Actual segfaults in libstdc++" -- are sorted out.