On Thu, 2018-10-11 at 18:26 +0100, John Garry wrote: > > > Yeah, I have a patch now to reference it, but I don't see anything from > > > -Wvla with gcc 8.1? > > > > I'm using a 7.3.1-based toolchain > > > > > > > > See > > > https://git.kernel.org/pub/scm/linux/kernel/git/jberg/mac80211-next.git/commit/?id=3d7af878357acd9e37fc156928106f1a969c8942 > > > > > > and its parent. > > > > > > Do you see -Wvla warnings there? Any idea how I could reproduce them? > > > > I'll try it, thanks > > 3d7af878357acd9e37f builds ok. However I am using 20181010-next (I'm not > sure what yours is based on), and I just noticed that it includes this > new guy: > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/Makefile?h=next-20181011&id=bc5701d8e27fd8beaf895176982fc6a97878f3b Right, but I added -Wvla by adding subdir-ccflags-y to my Makefile for this test, and I don't see the warning. I tried with gcc 7.3.1 too now (Fedora 27) and it doesn't provoke the warning, even if apply bc5701d8e27fd (manually). I did ensure with V=1 that it shows up on the compiler command line. This is on x86-64, are you using something else? Hmm. However, I have another trick: #define __NLA_ENSURE(condition) (0 * sizeof(struct { unsigned int x:1 - 2*!(condition);})) or, in this context, #define BUILD_BUG_ON_RET_ZERO(cond) (0 * sizeof(struct { unsigned int x:1 - 2*!(condition);})) What do you think? johannes
