[Piglit] [PATCH 2/3] Use alloca instead of variable length arrays

[Dylan Baker]

Is this actually necessary? I though that we required MSVC 2013 u4,
because it has c99 support.

Also, dma_buf tests require libdrm_intel, which doesn't exist/work on
windows, so I don't think anyone will be building them with msvc anytime
soon.

Dylan

On Fri, Feb 06, 2015 at 11:49:08AM -0500, Jan Vesely wrote:
> ping
> 
> On Fri, 2014-12-12 at 19:13 -0500, Jan Vesely wrote:
> > On Fri, 2014-12-12 at 14:49 -0800, Matt Turner wrote:
> > > On Fri, Dec 12, 2014 at 2:13 PM, Jan Vesely <jan.vesely at rutgers.edu> wrote:
> > > > On Fri, 2014-12-12 at 13:37 -0800, Matt Turner wrote:
> > > >> On Fri, Dec 12, 2014 at 1:23 PM, Jan Vesely <jan.vesely at rutgers.edu> wrote:
> > > >> > On Fri, 2014-12-12 at 12:58 -0800, Matt Turner wrote:
> > > >> >> I'm curious what the motivation for removing variably-sized arrays is,
> > > >> >> but if I accept that that's a good thing to do then the first patch
> > > >> >> makes sense, but I don't understand this one.
> > > >> >>
> > > >> >> How is a variably-size array different from using alloca()?
> > > >> >
> > > >> > variable size arrays are a c99 feature not supported by msvc (that's why
> > > >> > there is a warning). I don't know which parts actually do need to build
> > > >> > using msvc, but it seemed like a good idea to reduce warning output (and
> > > >> > improve consistency with code that needs to build using msvc).
> > > >> >
> > > >> > In the first patch I used alloca+free, because it looked nicer than
> > > >> > doing size arithmetic. The other cases allocate byte arrays, and the
> > > >> > only difference is that alloca (_alloca) is supported by msvc.
> > > >>
> > > >> Okay, then this patch doesn't do anything useful, since these tests
> > > >> shouldn't be built with MSVC. dma_bufs are a Linux thing.
> > > >
> > > > yes, I understand that, the point was not to build them using msvc.
> > > >
> > > > the patch usefulness is in enabling switch Wvla to error instead of
> > > > warning. other than that, it just reduces warning output.
> > > 
> > > Ah, I see. Okay.
> > > 
> > > For my own curiosity, does this actually change the compiled code?
> > 
> > Looks like the vla version uses fewer instructions but the code size is
> > the same (for -O3).
> > I'm using gcc 4.9.2 that comes with F21
> > 
> > I have attached release and debug versions of
> > ext_image_dma_buf_import-ownership_transfer piglit_display()
> > if you're interested
> > 
> > jan
> > 
> > 
> 
> -- 
> Jan Vesely <jan.vesely at rutgers.edu>



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