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* middle-end/7736: gcc destroys stack layout when a local label is used
@ 2002-08-27 13:36 piotr.wyderski
0 siblings, 0 replies; 3+ messages in thread
From: piotr.wyderski @ 2002-08-27 13:36 UTC (permalink / raw)
To: gcc-gnats
>Number: 7736
>Category: middle-end
>Synopsis: gcc destroys stack layout when a local label is used
>Confidential: no
>Severity: critical
>Priority: medium
>Responsible: unassigned
>State: open
>Class: wrong-code
>Submitter-Id: net
>Arrival-Date: Tue Aug 27 10:26:01 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator: Piotr Wyderski
>Release: 3.0, 3.0.1, 3.0.4 (supposably all versions)
>Organization:
>Environment:
IA-32 Celeron, Red Hat Linux 7.2.
>Description:
When a local label is used in a function, gcc generates
broken code. The simplest example is:
void test(void) {
({ __label__ x;
x:
goto x;
});
}
gcc -S -O2 1.c, which produces:
.file "1.c"
.text
.align 16
.globl test
.type test,@function
test:
pushl %ebp
movl %esp, %ebp
subl $8, %esp
.L2:
jmp .L2
.Lfe1:
.size test,.Lfe1-test
.ident "GCC: (GNU) 3.0.4"
The error is because of "subl $8,%esp". This is NOT an alignment issue,
because sometimes (when a function is slightly larger) it produces things
like:
push edx
push edx
// very small function body here, which _doesn't_ use edx nor ecx.
pop ecx
pop eax
ret
There's no such an error when a global (i.e. normal) label is used
instead, code is generated properly. I've tested that on many ways
and I am completely sure this wrong behaviour is because of local
labels. When the function code is quite large, it causes a crash of
the application, thus this bug is critical.
>How-To-Repeat:
Use a local label in a (small) function and read assembly output.
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted:
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: middle-end/7736: gcc destroys stack layout when a local label is used
@ 2003-03-25 18:30 neroden
0 siblings, 0 replies; 3+ messages in thread
From: neroden @ 2003-03-25 18:30 UTC (permalink / raw)
To: gcc-bugs, gcc-prs, nobody, piotr.wyderski
Synopsis: gcc destroys stack layout when a local label is used
State-Changed-From-To: feedback->closed
State-Changed-By: neroden
State-Changed-When: Tue Mar 25 18:29:38 2003
State-Changed-Why:
Not clear that there's a bug. No feedback 3 months.
http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=7736
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: middle-end/7736: gcc destroys stack layout when a local label is used
@ 2002-12-20 21:39 bangerth
0 siblings, 0 replies; 3+ messages in thread
From: bangerth @ 2002-12-20 21:39 UTC (permalink / raw)
To: gcc-bugs, gcc-prs, nobody, piotr.wyderski
Synopsis: gcc destroys stack layout when a local label is used
State-Changed-From-To: open->feedback
State-Changed-By: bangerth
State-Changed-When: Fri Dec 20 21:39:15 2002
State-Changed-Why:
I can't see what is wrong with the function for which you
show the assembler output: you have an infinite loop, and
the assembler code reflects that. What exactly is it that
you consider a problem in this code snippet?
If the problem does only appear in larger functions than
the one you present, you will have to give us an example
of such a function.
Regards
Wolfgang
PS: Just for the record -- all more recent versions of
gcc create virtually the same code.
http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=7736
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2003-03-25 18:29 UTC | newest]
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2002-08-27 13:36 middle-end/7736: gcc destroys stack layout when a local label is used piotr.wyderski
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2003-03-25 18:30 neroden
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