Re: EXC_BAD_ACCESS on Mac

[山本和彦]

Hi,

>> I'm using Emacs HEAD ("24.3.50.1") on Mac. It *often* crashes when I'm
>> reading e-mail messages with Mew. I took trace with gdb. The value of
>> "glyph" is 0x5bfe and this causes EXC_BAD_ACCESS.
> 
> The value of 'glyph' is a pointer to a structure, so this value is
> meaningless.  The contents of that structure might be interesting,
> though.

I don't think so. I think the broken pointer value of 'glyph' causes
EXC_BAD_ACCESS. Note that EXC_BAD_ACCESS is a Mac specific error.

In another catch, let's see what happens if we evaluate each value:

Program received signal EXC_BAD_ACCESS, Could not access memory.
Reason: 13 at address: 0x0000000000000000
0x000000010001b317 in get_glyph_face_and_encoding (f=0x10b3c7d88, glyph=0x5f62, 
char2b=0x7fff5fbfb260, two_byte_p=0x7fff5fbfb224) at xdisp.c:22544
22544           code = face->font->driver->encode_char (face->font, 
glyph->u.ch);
(gdb) p face
$1 = (struct face *) 0x10edc2120
(gdb) p face->font
$2 = (struct font *) 0x10b3c7d88
(gdb) p face->font->driver
$3 = (struct font_driver *) 0x10200303a
(gdb) p face->font->driver->encode_char
$4 = (unsigned int (*)(struct font *, int)) 0x33a9000000000000
(gdb) p face->font
$5 = (struct font *) 0x10b3c7d88
(gdb) p glyph
$6 = (struct glyph *) 0x5f62
(gdb) p glyph->u.ch
Cannot access memory at address 0x5f8a

So, I guess that some code break the value of glyph.

I cannot show minimum sequence to reproduce this crash. But it often
happens.

--Kazu