Closed Bug 50782 Opened 20 years ago Closed 19 years ago

ILTRACE core dump in gif.cpp due to LOCAL il_log_module var


(Core :: ImageLib, defect, P1, critical)






(Reporter: harbaugh, Assigned: cls)




(5 files)

(NOTE: proposed fix is included)
'il_log_module' is re-declared locally in gif.cpp and set to NULL.
This causes an attempt to dereference a NULL pointer in the ILTRACE
expansion (files gif.cpp, jpeg.cpp and ipng.cpp).  Hence the program
segfaults before displaying a window.

  remove lines 80-81 of gif.cpp, which are actually a *LOCAL*
  redeclaration of variables that should be GLOBAL

    80:   int il_debug;
    81:   PRLogModuleInfo *il_log_module = NULL;

  The 'true' declaration/initialization of these variables occurs
  in ilclient.cpp.  Similar lines should be removed from jpeg.cpp
  and ipng.cpp

  line 80 factors into this because the local 'il_debug' is
  not initialized and hence can contain random junk

========= analysis ===========
Debugger shows that SEGV occurs upon reaching line 859 of gif.cpp:

% ./mozilla -g -d ladebug 
     ./ -g -d ladebug ./mozilla-bin 
     /usr/bin/ladebug ./mozilla-bin 
     Welcome to the Ladebug Debugger Version 4.0-62 (built Jun 23 2000)
     object file name: ./mozilla-bin 
     core file name: 
     Warning: cannot open core file : 
     Reading symbolic information ...done
     (ladebug) use ../../modules/libimg/gifcom
     Directory search path for source files:
      . ../../modules/libimg/gifcom
     (ladebug) run
     nsNativeComponentLoader: autoregistering begins.
     nsNativeComponentLoader: autoregistering succeeded
     nNCL: registering deferred (0)
     GFX: dpi=96 t2p=0.0666667 p2t=15 depth=16
     WEBSHELL+ = 1
     Initialized app shell component {18c2f989-b09f-11d2-bcde-00805f0e1353},
     Initialized app shell component {33e569b0-40f8-11d4-9a41-000064657374},
     ProfileName : default
     ProfileDir  : /users/primgr/harbaugh/.mozilla/default
     CSSLoaderImpl::LoadAgentSheet: Load of URL
'file:///users/primgr/harbaugh/.mozilla/default/chrome/user.css' failed.  Error
code: 16389
     WEBSHELL+ = 2
     Enabling Quirk StyleSheet
     Note: verifyreflow is disabled
     Note: styleverifytree is disabled
     Note: frameverifytree is disabled
     Enabling Quirk StyleSheet
     WARNING: chrome: failed to get base url for
chrome://necko/locale/ -- using wacky default, file
nsChromeRegistry.cpp, line 507
     Obtained name of Personal Toolbar from bookmarks string bundle.
     Start reading in bookmarks.html
     Finished reading in bookmarks.html  (78125 microseconds)
     WEBSHELL+ = 3
     Thread received signal SEGV
     stopped at [int il_gif_write(il_container*, const PRUint8*, int32):859
         859         ILTRACE(9,("il:gif: state %d len %d buf %u p %u q %u ep

     Preprocessing gif.cpp and examining the output shows *TWO* 
     declarations of il_log_module.  The first is an 'extern'
     from if_struct.h; the second is local (line 81 of gif.cpp)
     and sets il_log_module to NULL.

     Line 859 expands to

        { if(il_debug>1) {do { if (((il_log_module)->level >= (1))) {
PR_LogPrint ("il:gif: ...

     where the attempt to dereference (il_log_module)->level
     SEGFAULTS since the local il_log_module overrides the global.
Severity: normal → critical
I did test the proposed fix and it works.  The only
question is whether it will adversely affect other platforms.
    I am attaching the preprocessed output of gif.cpp that you asked me for.
This is with the 6.1 compiler under Tru64 4.0D.
Attached patch Patch to fix bugSplinter Review
pnunn: You look like the person who gets to approve this change if you like it,
and Blame says its your code anyway so thats even better.  I asked for a
reviewer on the newsgroup, so if they say it looks good and you say it looks
good I will check it in.
This is a slam dunk.  I can review and approve, be good if pnunn gave r= too. 
Please get this in before any branch is cut from the trunk.

Ever confirmed: true
I would like to see the lines removed as originally proposed instead of
littering libimg with "#if 0" junk.  Clean sweep alternative attached.
Brendan, can you review/approve tor's patch.  He found the same problem in
several other files.
We also need to have these global symbol conflicts resolved for static
components (bug 46775) to work.
Blocks: 46775
r: pnunn
If someone else can check this in. I am swamped.
And some of you Mozillittes can check in easier than
I, a dreaded Netscapian, can.
Target Milestone: --- → M18
Its already in my tree.  Ill check it (tor's patch) in as soon as the tree opens.
much thanks.
Its checked in
Closed: 20 years ago
Resolution: --- → FIXED
This patch breaks the mac.  Should I just #ifdef the code so that its only there
for that platform?
Resolution: FIXED → ---
Attaching new fix
breandan || pnunn,
   Could one of you review this new patch?
Hmmm.  We're trying to make these local versions of the symbols go away, right?  
If they can't go away on Mac, then we've done something wrong somewhere.  This 
patch may be good enough to get the work in for the other platforms, but to me it 
looks like it means there's still more work to be done on Mac with respect to 
this bug.  I can only r= this patch on the condition that we're still working on 
the right completely cross-platform fix.
Updating QA Contact
QA Contact: paw → tpreston
Looks like these changes were checked in already ... and they break the Win32 
debug builds. With undefined symbols for il_log_module and il_debug.

You have to also undefine the ILTRACE() macro to get things going again.
As sheriff, I have backed out the changes, caused build bustage on win32, also I
think this can be done xp
    The phone company dug through DSL line the other day, so I have been
off the internet for a few days.  I was able to read my email this 
morning only to discover that I broke the debug windows builds on the
27th while trying to fix bug 50872.  I watched tinderbox after I did
that checkin, and they all stayed green so I was quite supprised this
morning to learn that I had broken things.  My guess is that both the
windows tinderbox machines are running optimized builds?  In any event,
after the tinderboxes went green I left, and was not available to help
sort out the bustage I had caused.  I am truly sorry for causing problems.
    This was my second attempt at fixing 50872, and given that I have
broken some platform each time I am now quite scared of trying again.
I am only able to test my code under Linux, and that is obviously not
sufficient for this code.  I am going to see if I can find someone at
NS who has access to all 3 platforms to take ownership of this bug.
Target Milestone: M18 → Future
Why not just remove those il_debug, il_log_module and ILTRACE from gif.cpp, 
ipng.cpp, jpeg.cpp. We just lost some debug information. That should solve
all the problem. If somebody believe it is really necessary to have those
information, we may have to define local version in different names, like
ipng_log_module, ipng_debug, IPNG_TRACE. For those small modules, I doubt
its necessity.
Blocks: 61525
*** Bug 62024 has been marked as a duplicate of this bug. ***
Depends on: 70938
*** Bug 67865 has been marked as a duplicate of this bug. ***
Whats the progress on this bug were still seeing people having this crash on them.
There has been no progress as far as I know.  We know whats going on, and
several proposals to fix this have been put on the table.  Someone with some
athority (pnunn?) needs to pick one. FWIW, I like Shanjian Li's proposal the
best.  Lets just remove this code.  We dont need it and its causing problems.
Taking bug.
Assignee: pnunn → cls
Keywords: mozilla0.9
OS: OSF/1 → All
Priority: P3 → P1
Hardware: DEC → All
Target Milestone: Future → mozilla0.9
Verified 03/18/01 ptach on Mac debug for gif, jpg, mng and png decoder projects 
as wells as libimg project.  Still need verification on opt build
Verified debug & opt on win32.

Patch checked in.  Marking fixed.
Closed: 20 years ago19 years ago
Resolution: --- → FIXED
Verified fix checked into
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