> From: Mattias Rönnblom [mailto:hof...@lysator.liu.se] > Sent: Wednesday, 10 April 2024 09.32 > > On 2024-04-08 17:53, Morten Brørup wrote: > >> From: Tyler Retzlaff [mailto:roret...@linux.microsoft.com] > >> Sent: Monday, 8 April 2024 17.27 > >>
[...] > >> Looks like we need to discuss this at the next techboard meeting. > >> > >> * MSVC doesn't support C11 optional VLAs (and never will). > >> * alloca() is an alternative that is available on all platforms/toolchain > >> combinations. > >> * it's reasonable for some VLAs to be turned into regular arrays but it > >> would be unsatisfactory to be stuck waiting discussions of defining new > >> constant expression macros on a per-use basis. > > > > We must generally stop using VLAs, for many reasons. > > What reasons would that be? And which of those reasons are not also > reasons to stop using alloca(). The reasons against VLAs are the same as why MSVC doesn’t support them; primarily that they are insecure. The reasons against VLAs and alloca() are the same, except MSVC supports alloca(). > > > The only available 1:1 replacement is alloca(), so we have to accept that. > > > > If anyone still cares about improvements, we can turn alloca()'d arrays into > regular arrays after this patch series. > > > > Alternatives to VLAs are very interesting discussions, but let's not stall > MSVC progress because of it! > > > > What is this supposed to mean? Finding alternatives to VLAs are required > to make progress of MSVC support in DPDK. It means that not enough people contribute to discussing and implementing alternatives, so we have to use the 1:1 replacement alternative, alloca(), to avoid stalling DPDK support for MSVC. We can discuss and implement alternatives at any time, if anybody cares. > > >> * there is resistance to using alloca() vs VLA so my proposal is to > >> change only the code that is built to target windows. > > > > I would prefer to get rid of them all, so the CI can build with -Wvla to > prevent them from being introduced again. > > Not a strong preference. > > On the other hand, the CI's MSVC builds will catch them if used for a > Windows target. > > And limiting to Windows code reduces the amount of work, so that's probably > the most realistic solution. > >
