GNU bug report logs - #9983
valgrind warning in draw_glyphs

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Dan Nicolaescu <dann <at> gnu.org>
Subject: bug#9983: closed (Re: bug#9983: valgrind warning in draw_glyphs)
Date: Mon, 07 Nov 2011 15:25:03 +0000

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Your bug report

#9983: valgrind warning in draw_glyphs

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 9983 <at> debbugs.gnu.org.

-- 
9983: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=9983
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Dan Nicolaescu <dann <at> gnu.org>
To: Andreas Schwab <schwab <at> linux-m68k.org>
Cc: Eli Zaretskii <eliz <at> gnu.org>, 9983-close <at> debbugs.gnu.org
Subject: Re: bug#9983: valgrind warning in draw_glyphs
Date: Mon, 07 Nov 2011 10:21:18 -0500

Andreas Schwab <schwab <at> linux-m68k.org> writes:

> Dan Nicolaescu <dann <at> gnu.org> writes:
>
>> so it looks like check_mouse_face is tested after mouse_beg_col.
>
> That is perfectly ok under the as-if rule.  See also

Right.  Closing this bug then.

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From: Dan Nicolaescu <dann <at> gnu.org>
To: bug-gnu-emacs <at> gnu.org
Subject: valgrind warning in draw_glyphs
Date: Sun, 06 Nov 2011 23:36:42 -0500

trunk with lucid toolkit
valgrind ./temacs -Q
gives this warning (not sure exactly when, just playing with the menus
and tooltips, the only "editing" action was to run a grep)





==2341== Conditional jump or move depends on uninitialised value(s)
==2341==    at 0x44CDDA: draw_glyphs (xdisp.c:22981)
==2341==    by 0x44D9FC: expose_area (xdisp.c:27401)
==2341==    by 0x44DDA8: expose_line (xdisp.c:27426)
==2341==    by 0x45B6AA: expose_window (xdisp.c:27653)
==2341==    by 0x45C0DA: expose_window_tree (xdisp.c:27725)
==2341==    by 0x45C0B0: expose_window_tree (xdisp.c:27723)
==2341==    by 0x45C16E: expose_frame (xdisp.c:27780)
==2341==    by 0x4C188D: handle_one_xevent (xterm.c:6219)
==2341==    by 0x4C2F56: XTread_socket (xterm.c:7148)
==2341==    by 0x4F2F26: read_avail_input (keyboard.c:6821)
==2341==    by 0x4F3049: handle_async_input (keyboard.c:7149)
==2341==    by 0x4F26A4: process_pending_signals (keyboard.c:7165)
==2341==  Uninitialised value was created by a stack allocation
==2341==    at 0x44AAD3: draw_glyphs (xdisp.c:22835)
==2341== 


The warning is for this:
        if (check_mouse_face
              && mouse_beg_col < start && mouse_end_col > i)

it looks like mouse_beg_col and mouse_end_col could be left uninitialized a few lines above.

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