On Thu, May 13, 2021 at 12:51:45PM +0200, Jaromír Doleček wrote: > Le jeu. 13 mai 2021 à 01:04, Joerg Sonnenberger <jo...@bec.de> a écrit : > > > > On Wed, May 12, 2021 at 08:32:20PM +0200, Jaromír Doleček wrote: > > > Le mer. 12 mai 2021 à 13:50, Joerg Sonnenberger <jo...@bec.de> a écrit : > > > > > > > > On Wed, May 12, 2021 at 08:38:39AM +0200, Jaromír Doleček wrote: > > > > > would it be a bad thing to add a compatibility <alloca.h> which would > > > > > use the builtin alloca() instead of the libc one when available? > > > > > > > > > > e.g. MySQL 8.0.* seems to rely on this. > > > > > > > > We provide it in stdlib.h as long as a standard mode is not set. > > > > I don't see the point of adding alloca.h. > > > > > > We don't provide the builtin in stdlib.h. > > > > Yes, we do. > > No we don't, unless you are using PCC :D > > The block in <stdlib.h> only provides an alloca(3) prototype, and only > if the compiler already #defines alloca as __builtin_alloca. > > While this works for gcc in some -std modes (e.g. gnu++14), it does > not in others (c++14, c++11).
Your analysis is wrong. We don't provide a prototype in standard modes as that violates the user request. The prototype is enough to trigger the builtin logic in GCC and Clang. Joerg
