[Pkg-sdl-maintainers] Bug#354524: libsdl1.2: 1.2.9-1 crashes windowed SDL programs

[Mike Kasick]

On Sun, Feb 26, 2006 at 09:42:09PM -0500, Jeff Bonham wrote:

> When downgraded to 1.2.9-0 packages this bug disappears.  I reproduced
> it with dosbox and enigma.

I noticed the same problem when running qemu after upgrading this evening.
The emulator would segfault right after startup.  Here's the gdb trace:

22:44:04 epitome:/usr/local/src/qemu-0.8.0# gdb i386-softmmu/qemu
GNU gdb 6.4-debian
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This GDB was configured as "i486-linux-gnu"...Using host libthread_db library "/lib/tls/libthread_db.so.1".

(gdb) r -cdrom /dev/hdc
Starting program: /scratch/local/src/qemu-0.8.0/i386-softmmu/qemu -cdrom /dev/hdc
[Thread debugging using libthread_db enabled]
[New Thread -1212106464 (LWP 27309)]
Could not open '/dev/kqemu' - QEMU acceleration layer not activated

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread -1212106464 (LWP 27309)]
0xb7c74d57 in XLookupString () from /usr/X11R6/lib/libX11.so.6
(gdb) bt
#0  0xb7c74d57 in XLookupString () from /usr/X11R6/lib/libX11.so.6
#1  0xb7f26617 in X11_TranslateKey () from /usr/lib/libSDL-1.2.so.0
#2  0xb7f26be3 in X11_SetKeyboardState () from /usr/lib/libSDL-1.2.so.0
#3  0xb7f270f9 in X11_PumpEvents () from /usr/lib/libSDL-1.2.so.0
#4  0xb7f3fd25 in SDL_PumpEvents () from /usr/lib/libSDL-1.2.so.0
#5  0xb7f3fd67 in SDL_PollEvent () from /usr/lib/libSDL-1.2.so.0
#6  0x0809ae48 in sdl_refresh (ds=0x8118ce0)
    at /usr/local/src/qemu-0.8.0/sdl.c:465
#7  0x0804f720 in gui_update (opaque=0x0)
    at /usr/local/src/qemu-0.8.0/vl.c:3674
#8  0x0804b8b7 in qemu_run_timers (ptimer_head=0x8118d24, current_time=4631556)
    at /usr/local/src/qemu-0.8.0/vl.c:767
#9  0x0804fe3d in main_loop_wait (timeout=0)
    at /usr/local/src/qemu-0.8.0/vl.c:3887
#10 0x0804ffd8 in main_loop () at /usr/local/src/qemu-0.8.0/vl.c:3945
#11 0x080512bb in main (argc=3, argv=0xbfbd9d94)
    at /usr/local/src/qemu-0.8.0/vl.c:5051

Since I just upgraded the SDL packages to 1.2.9-1, it seemed suspect.
Here's what the change log says:

  * debian/patches/005_x11_keysym_fix.diff:
    + Patch courtesy of Jochen Voss to fix lookup of keys using eg. the
      AltGr modifier (Closes: #299864).

And the patch:

--- SDL-1.2.7+1.2.8cvs20041007.orig/src/video/x11/SDL_x11events.c       2005-03-16 23:39:50.000000000 +0000
+++ SDL-1.2.7+1.2.8cvs20041007/src/video/x11/SDL_x11events.c    2005-03-16 23:43:49.000000000 +0000
@@ -614,11 +614,12 @@
 SDL_keysym *X11_TranslateKey(Display *display, XKeyEvent *xkey, KeyCode kc,
                             SDL_keysym *keysym)
 {
+       char buffer[8];
        KeySym xsym;

        /* Get the raw keyboard scancode */
        keysym->scancode = kc;
-       xsym = XKeycodeToKeysym(display, kc, 0);
+       XLookupString(xkey, buffer, 8, &xsym, NULL);
 #ifdef DEBUG_KEYS
        fprintf(stderr, "Translating key 0x%.4x (%d)\n", xsym, kc);
 #endif

So I don't know what the proper invocation of XLookupString() is, but I bet
this is passing a bogus pointer.  Someone should look at this patch more
carefully.