[FFmpeg-trac] #5231(avcodec:closed): Crashes in ff_deblock_v_luma_8_sse2
FFmpeg
trac at avcodec.org
Fri Oct 7 23:17:22 EEST 2016
#5231: Crashes in ff_deblock_v_luma_8_sse2
-------------------------------------+-------------------------------------
Reporter: mi | Owner:
Type: defect | Status: closed
Priority: important | Component: avcodec
Version: git-master | Resolution: fixed
Keywords: h264 crash | Blocked By:
SIGSEGV | Reproduced by developer: 1
Blocking: |
Analyzed by developer: 0 |
-------------------------------------+-------------------------------------
Comment (by cehoyos):
Replying to [comment:25 mi]:
> Replying to [comment:24 cehoyos]:
> {{{
> --- a/configure
> +++ b/configure
> @@ -6202,6 +6202,7 @@ elif enabled llvm_gcc; then
> check_cflags -mllvm -stack-alignment=16
> elif enabled clang; then
> check_cflags -mllvm -stack-alignment=16
> + check_cflags -mstack-alignment=16
> check_cflags -Qunused-arguments
> check_cflags -Werror=implicit-function-declaration
> check_cflags -Werror=missing-prototypes
> }}}
> Does this not cause a pessimization in other parts of the code, though?
I don't think so, as explained by the BSD developers, this is the default
on (all) other systems, it was also always meant to be used (see the line
{{{-mllvm -stack-alignment=16}}} above).
> That was my worry -- that by setting the stack-alignment to a non-
default value to solve a problem in one function slows things down (or
increases memory use) everywhere else...
That would be true for {{{-mstackrealign}}} which I fear may be necessary
to fix the original issue with firefox;-(
As said, I did not test with firefox.
> > Thanks to Mikhail
> You are welcome. I'll keep your account on the box active. In addition
to clang-3.4.1 (a.k.a. `cc`) and gcc-4.2.1 (a.k.a. `gcc`), it has the
latest versions of clang-3.6 (`clang36`), 3.7 (`clang37`), 3.8 (`clang38`)
I only tested clang 3.8 (and gcc 4.2, see below).
> and gcc-6 (`gcc6`).
I had not found this one;-(
It is the only compiler that really works for FFmpeg on FreeBSD (gcc 4.2
is broken, configure warns about it)
Ideally, you would first test with clang and {{{--extra-cflags=-mstack-
alignment=16}}}, if this does not help, you can try {{{--cc=gcc6}}}. If
both still crash with firefox, one alternative is to also compile firefox
with increased stack alignment.
--
Ticket URL: <https://trac.ffmpeg.org/ticket/5231#comment:26>
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