Re: [libvirt] [PATCH] Raise the frame limit for tests

On Mon, Jan 22, 2018 at 01:47:24PM +0100, Michal Privoznik wrote: > On 01/22/2018 01:22 PM, Daniel P. Berrange wrote: > > On Mon, Jan 22, 2018 at 12:49:12PM +0100, Martin Kletzander wrote: > > > On Thu, Jan 18, 2018 at 10:16:55AM +0100, Ján Tomko wrote: > > > > After the latest CPU additions, the build fails with clang: > > > > cputest.c:905:1: error: stack frame size of 26136 bytes > > > > in function 'mymain' [-Werror,-Wframe-larger-than=] > > > > > > > > Raise the relaxed limit which is used for tests. > > > > --- > > > > m4/virt-compile-warnings.m4 | 2 +- > > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > > > Pushed as a build breaker fix > > > > > > > > diff --git a/m4/virt-compile-warnings.m4 b/m4/virt-compile-warnings.m4 > > > > index f18a08a8f..b9c974842 100644 > > > > --- a/m4/virt-compile-warnings.m4 > > > > +++ b/m4/virt-compile-warnings.m4 > > > > @@ -200,7 +200,7 @@ AC_DEFUN([LIBVIRT_COMPILE_WARNINGS],[ > > > > # but using 1024 bytes sized buffers (mostly for virStrerror) > > > > # stops us from going down further > > > > gl_WARN_ADD([-Wframe-larger-than=4096], [STRICT_FRAME_LIMIT_CFLAGS]) > > > > - gl_WARN_ADD([-Wframe-larger-than=25600], [RELAXED_FRAME_LIMIT_CFLAGS]) > > > > + gl_WARN_ADD([-Wframe-larger-than=32768], [RELAXED_FRAME_LIMIT_CFLAGS]) > > > > > > > > > > Remind me again why don't we do -Wno-frame-larger-than (or something to that > > > effect) for tests? Is it just because "We should fix it at some point"? I > > > can't really recall the reasoning behind that (and if it is still valid) even > > > though I already asked for it. > > > > I don't think there's a strong reason, given the way we currently write > > tests with huge amounts of stack variables. > > > > For -Wframe-larger-than to be useful, we'd need to move all the big data > > blobs to be static, global variables. > Or simply use compiler that honours variable lifetime. If a variable is > defined only in a block, compiler should be able to just reuse the > stack. I mean for the following case: > > do { > int x; > } while (0); > > do { > int y; > } while (0); > > I don't see any compelling reason for compiler to reserve two ints on > the stack. Or if it does, count it as one when comparing agains > -Wframe-larger-than. > We can do that ourselves, even though it's not really great thing to do. Just reset the one struct and reuse it. I added it (and future research) as an idea to GSoC ideas. Let's see if someone rewrites that.