[MinGW-notify] [ mingw-Bugs-2819860 ] Runtime crash when compiled under GCC 4.4.0

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Bugs item #2819860, was opened at 2009-07-10 15:00
Message generated for change (Comment added) made by earnie
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Category: gcc
Group: None
>Status: Closed
>Resolution: Out of Date
Priority: 5
Private: No
Submitted By: Anthony (anthonypenn)
Assigned to: Nobody/Anonymous (nobody)
Summary: Runtime crash when compiled under GCC 4.4.0

Initial Comment:
Synopsis:
---------------

I've recently switched compilation of my project to GCC 4.4.0 (from GCC 3.4.5) and the result is an odd and inconsistent runtime crash.
I've narrowed it down to a switch statement (handling win32 API events); however after further investigation I've found that:
- the runtime crash occurs when a certain case label is included in the switch
- the value of the label is not the problem (I've tried arbitrary integers), the mere *presence of* the case seems to trigger the crash.
- for the sake of testing, I have made the case completely empty and ensured it is never reached
- the crash ONLY occurs when optimizations are enabled (-s -O3)

The mere presence of a case that is never reached in a switch statement should theoretically have no effect, which has prompted me to recognize this as a bug in GCC 4.4.0.

The project is large and no simple test case can be constructed. Given the nature of occurrence the entire project need be compiled to reproduce it; however from the inclusion/exclusion of an empty case statement that is never reached making the only make-or-break difference while compiling under optimizations, it seems that something is awry in the optimized code generated for switch statements).
The observed bug can be summarized as this:
switch( X ) {
case SOME_LABEL:
break;
// inclusion of this case while compiling under GCC 4.4.0 with full optimizations causes the crash
// whereas GCC 3.4.5 produces no such problem
case PROBLEMATIC_LABEL_THAT_IS_EMPTY_AND_NEVER_REACHED: // 
break;
}

As mentioned above, I suspect optimizations in GCC 4.4.0 are producing code that is not robust for this case.
If any more information is required, just let me know, I can provide entire source and makefile if need-be.
Until further notice however, I will be compiling under GCC 3.4.5 so as to avoid this bug.

Environment Information:
----------------------------------------

Windows XP (SP2)

gcc --version:
gcc (GCC) 4.4.0
Copyright (C) 2009 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

ld -v:
GNU ld (GNU Binutils) 2.19.1

shell: cmd.exe (with compilation setup through mingw32-make)

mingw32-make --version:
GNU Make 3.81
Copyright (C) 2006  Free Software Foundation, Inc.
This is free software; see the source for copying conditions.
There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
PARTICULAR PURPOSE.

This program built for i686-pc-mingw32

----------------------------------------------------------------------

>Comment By: Earnie Boyd (earnie)
Date: 2012-06-14 07:16

Message:
Optimization is a best guess by the compiler.  It may require you to mark
your code with a "do not optimize" marker.  If you are still having
problems with a more recent version of GCC please open a new issue.  And we
really must have a simple test case to help resolve the issues.

----------------------------------------------------------------------

You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=102435&aid=2819860&group_id=2435