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Re: [libvirt] [PATCH] maint: increase stack frame size limit



  Eric Blake wrote:

> On 05/08/2015 12:23 AM, Roman Bogorodskiy wrote:
> >   Roman Bogorodskiy wrote:
> > 
> >>   Roman Bogorodskiy wrote:
> >>
> >>> Currently the stack frame size limit is set to 4096 and it started to
> >>> cause an error like this:
> >>>
> >>> virshtest.c:253:1: error: stack frame size of 5512 bytes in function
> >>> 'mymain' [-Werror,-Wframe-larger-than=]
> >>> mymain(void)
> >>> ^
> >>> 1 error generated.
> >>>
> >>> Increase it to 6144.
> >>
> >> Worth to mention that it's started to show up after updating to clang
> >> 3.6.
> > 
> > Any comments on this?
> 
> Have you reported a possible clang regression bug to the clang folks?
> Or is the new clang version the first one to support what was originally
> only gcc's -Wframe-larger-than?  At any rate, why does clang require a
> larger stack than gcc?  It sounds like in addition to fixing the
> virshtest.c file to quit stack-allocating such a large amount of space,
> that you should also be letting the clang compiler folks know about
> their weakness.

I wasn't absolutely sure that it is a clang problem. However, I did a
check now on the same libvirt revision and on the same system with
different clang versions and figured out that things work fine with:

clang version 3.4.2 (tags/RELEASE_34/dot2-final)

but start breaking on:

clang version 3.5.2 (tags/RELEASE_352/final)

So it indeed makes sense to ask clang developers what's going on; will
do that.

I'll also try to figure out how to rewrite virshtest.c to quite
stack-allocation.

Thanks for the feedback!

Roman Bogorodskiy

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