bug#17962: 24.4.50; emacs_backtrace.txt

bug#17962: 24.4.50; emacs_backtrace.txt

[Drew Adams]

Exception 0xc0000005 at this address:
0105edbd

Backtrace:
01201baf
01201c20
010f4223
01118a2e
01118a09
01118a62
010011e6
764502ff
774374fb
773f9f41

At the time, I was in the debugger, and I hit d when the sexp to be
evaluated was (erase-buffer).  Dunno whether that helps.


In GNU Emacs 24.4.50.1 (i686-pc-mingw32)
 of 2014-06-28 on ODIEONE
Bzr revision: 117431 rgm@gnu.org-20140628015517-eku6hj8mpgcvfnso
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --prefix=/c/Devel/emacs/snapshot/trunk
 --enable-checking=yes,glyphs 'CFLAGS=-O0 -g3'
 LDFLAGS=-Lc:/Devel/emacs/lib 'CPPFLAGS=-DGC_MCHECK=1
 -Ic:/Devel/emacs/include''

bug#17962: 24.4.50; emacs_backtrace.txt

[Drew Adams]

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It seems to be systematic, but there is far too much to constitute a
recipe.  This time I was able to take a screenshot of *Backtrace*
(attached), just in case it helps. I guess the `erase-buffer' returned
before the crash.  Anyway, the last thing I did before the crash was
hit `d' to evaluate the (erase-buffer).

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bug#17962: 24.4.50; emacs_backtrace.txt

[Eli Zaretskii]

> Date: Sun, 6 Jul 2014 16:30:29 -0700 (PDT)
> From: Drew Adams <drew.adams@oracle.com>
> 
> Exception 0xc0000005 at this address:
> 0105edbd
> 
> Backtrace:
> 01201baf
> 01201c20
> 010f4223
> 01118a2e
> 01118a09
> 01118a62
> 010011e6
> 764502ff
> 774374fb
> 773f9f41
> 
> At the time, I was in the debugger, and I hit d when the sexp to be
> evaluated was (erase-buffer).  Dunno whether that helps.

This happens in display_line in the line marked below:

	  row->truncated_on_right_p = 1;
	  it->continuation_lines_width = 0;
	  reseat_at_next_visible_line_start (it, 0);
	  row->ends_at_zv_p = FETCH_BYTE (IT_BYTEPOS (*it) - 1) != '\n'; <<<<<<
	  break;
	}

A SIGSEGV there doesn't make much sense, but I added something in
emacs-24 revision 117374 to plumb the only possibility I could think
of.