I believe this can only happen if your font render is broken.
These are fixed fonts. It should be impossible that there is no
data in those pointers.
Is this recent source code? There have been bugs of this sort
fixed in the font renderers not long before 4.3. Though maybe
more exist. If this is easily reproducible I suspect you'll
find that it only happens with the freetype or xtt renders.
Mark.
On Thu, 27 Mar 2003, Gerd Knorr wrote:
> Hi,
>
> The X-Server crashes with a segfault due to a NULL pointer dereference,
> perfectly reproducable with a certain X client (mtt -- motif teletext
> decoder). Stacktrace below. Setting Option "no_accel" workarounds
> this. Hardware is a i386 machine with a Matrox G200. Anyone has a
> quick idea what this might be?
>
> cu,
>
> Gerd
>
> ==============================[ cut here ]==============================
> (gdb) c
> Continuing.
>
> Program received signal SIGSEGV, Segmentation fault.
> 0x0825de38 in DrawTETextScanlineWidth12 (base=0x40980000, glyphp=0x883aab0,
> line=0, width=12, glyphwidth=12) at xaaTEGlyph.c:868
> 868 bits |= SHIFT_L(glyphp[1][line],12);
> (gdb) bt
> #0 0x0825de38 in DrawTETextScanlineWidth12 (base=0x40980000,
> glyphp=0x883aab0, line=0, width=12, glyphwidth=12) at xaaTEGlyph.c:868
> #1 0x0825cfa3 in XAATEGlyphRendererScanlineLSBFirst (pScrn=0x881e8e0, x=1,
> y=91, w=12, h=19, skipleft=0, startline=1, glyphs=0x883aab0,
> glyphWidth=12, fg=0, bg=0, rop=12, planemask=0) at xaaTEGlyph.c:402
> #2 0x0823e611 in XAAGlyphBltTEColorExpansion (pScrn=0x881e8e0, xInit=1,
> yInit=142837096, font=0x0, fg=0, bg=-1, rop=3, planemask=4294967295,
> cclip=0x8945c7c, nglyph=1, gBase=0x0, ppci=0x883899c) at xaaTEText.c:281
> #3 0x0823e297 in XAAPolyText16TEColorExpansion (pDraw=0x8945c50,
> pGC=0x893f238, x=0, y=20, count=1, chars=0x893bf5b) at xaaTEText.c:97
> #4 0x0842fe9e in miSpritePolyText16 (pDrawable=0x8945c50, pGC=0x893f238, x=0,
> y=20, count=1, chars=0x893bf5b) at misprite.c:1848
> #5 0x08352206 in doPolyText (client=0x88ad5a0, c=0xbfffed00)
> at dixfonts.c:1392
> #6 0x083524ed in PolyText (client=0x88ad5a0, pDraw=0x0, pGC=0x0, pElt=0x0,
> endReq=0x0, xorg=0, yorg=0, reqType=142846640, did=0) at dixfonts.c:1473
> #7 0x0833548c in ProcPolyText (client=0x88ad5a0) at dispatch.c:2356
> #8 0x083314ca in Dispatch () at dispatch.c:450
> #9 0x08343271 in main (argc=2, argv=0xbffff244, envp=0xbffff250) at main.c:435
> #10 0x4005e8ae in __libc_start_main () from /lib/libc.so.6
> (gdb) print line
> $1 = 0
> (gdb) print glyph
> No symbol "glyph" in current context.
> (gdb) print glyphp
> $2 = (unsigned int **) 0x883aab0
> (gdb) print glyphp[0]
> $3 = (unsigned int *) 0x0
> (gdb) print glyphp[1]
> $4 = (unsigned int *) 0x0
> (gdb)
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