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

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.

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