Bug#783082: Aw: Re: linux-image-3.16.0-4-586: video players/browsers crash with 'illegal instruction' on i586

[Bernhard Übelacker]

Hello hikaru,
(I have tried to split the browser issue into a different bug #783293.)
When libav is built with this 3 attached changes then vlc and mplayer2 
are not crashing anymore.

This would need some more tests as I had only my qemu VM (which was way 
too slow) with one video file inside.

Kind regards,
Bernhard
--- libav-11.3/debian/confflags	2015-01-17 18:25:07.000000000 +0000
+++ try2/libav-11.3/debian/confflags	2015-04-23 23:27:54.279081295 +0000
@@ -180,7 +180,7 @@ shared_build_confflags += --enable-share
 shared_build_confflags += --disable-static
 # i386 shared builds must be optimized for 586, cf. #728928, #688384
 ifeq      ($(DEB_HOST_ARCH),i386)
-shared_build_confflags += --cpu=586
+shared_build_confflags += --cpu='i586'
 endif
 
 ## specific to arm architectures
Description: Workaround to build libav for i586 with GCC 4.9
Author: Bernhard Übelacker <bernha...@vr-web.de>

---
Bug: https://bugzilla.libav.org/show_bug.cgi?id=850
Bug-Debian: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=783082
Last-Update: 2015-04-24

--- libav-11.3.orig/configure
+++ libav-11.3/configure
@@ -3941,6 +3941,15 @@ EOF
     check_inline_asm ebx_available '""::"b"(0)' &&
         check_inline_asm ebx_available '"":::"%ebx"'
 
+    # workaround for bug debian#783082 / libav#850
+    # (by setting ebx unavailable we get HAVE_7REGS defined as 0
+    #  and C implementation of get_cabac_inline gets used)
+    case $cpu in
+        i586)
+            disable ebx_available
+        ;;
+    esac
+
     # check whether xmm clobbers are supported
     check_inline_asm xmm_clobbers '"":::"%xmm0"'
 
>From 9030c58a780a02fb8256cb75cd39275eaad786d1 Mon Sep 17 00:00:00 2001
From: Mikulas Patocka <miku...@artax.karlin.mff.cuni.cz>
Date: Mon, 15 Sep 2014 05:11:21 -0700
Subject: [PATCH] configure: Disable i686 for i586 and lower CPUs

---
 configure |    1 +
 1 file changed, 1 insertion(+)

diff --git a/configure b/configure
index 6e210bb..a7b3c55 100755
--- a/configure
+++ b/configure
@@ -3296,6 +3296,7 @@ elif enabled x86; then
     case $cpu in
         i[345]86|pentium)
             cpuflags="-march=$cpu"
+            disable i686
             disable mmx
         ;;
         # targets that do NOT support nopl and conditional mov (cmov)
-- 
1.7.10.4