On Sat, Aug 22, 2020 at 12:26 PM Segher Boessenkool <seg...@kernel.crashing.org> wrote: > [ There is GCC 4.9.4, no one should use an older 4.9. ] > > I mentioned 5 for a reason: the whole function this patch is to did not > exist before then! That does not mean the bug existed or did not exist > before GCC 5, but it does for example mean that a backport to 4.9 or > older isn't trivial at all. > > > I am asking myself who is using such ancient compilers? > > Some distros have a GCC 4.8 as system compiler. We allow building GCC > itself with a compiler that far back, for various reasons as well (and > this is very sharp already, the last mainline GCC 4.8 release is from > June 2015, not all that long ago at all). > > But, one reason this works is because people actually test it. Does > anyone actually test the kernel with old compilers? It isn't hard to > build a new compiler (because we make sure building a newer compiler > works with older compilers, etc. :-) ), and as you say, most distros > have newer compilers available nowadays.
We only recently changed the minimum from 4.6 to 4.8, and subsequently to 4.9. Most people have fairly recent compilers, but there are a number of notable kernel developers that intentionally stick to old versions because of compile speed. Each major compiler release adds about 4% overhead in total time to compile a kernel, so between gcc-4.6 and gcc-11 you add over 50% in build time. Arnd