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From: jojelino <jojelino@gmail.com>
Date: Thu, 20 Oct 2011 22:04:00 +0900
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Subject: Re: [Qemu-devel] gcc auto-omit-frame-pointer vs msvc longjmp
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To: qemu-devel@nongnu.org
Cc: gcc@gcc.gnu.org

On 2011-10-20 AM 6:05, Bob Breuer wrote:
>
> We probably have a difference in build or run environment.  I've
> double-checked with another machine and can get the same crash in
> longjmp when running the test executable on both WinXP and Win2k, but
> not on Win7.  So it looks like Microsoft may have changed this "feature"
> somewhere between WinXP and Win7.
YEES! It does crash in winxp.
>
> The msvcrt implementation of longjmp (or at least the one I'm looking
> at) does a ebp based access using the saved value of ebp.  Here's the
> relevant disassembly of longjmp:
>
> 0x7801e6f3 in longjmpex () from C:\WINNT\system32\msvcrt.dll
> (gdb) disas
> Dump of assembler code for function longjmpex:
>     0x7801e6ef<+0>:     mov    0x4(%esp),%ebx
> =>  0x7801e6f3<+4>:     mov    (%ebx),%ebp
> ...
>     0x7801e73d<+78>:    call   0x7800bd5e<abnormal_termination+56>
> ...
>     0x7800bd5e<+56>:    push   %ebx
>     0x7800bd5f<+57>:    push   %ecx
>     0x7800bd60<+58>:    mov    $0x7803dc64,%ebx
> =>  0x7800bd65<+63>:    mov    0x8(%ebp),%ecx
>
> It crashes on the access of 0x8(%ebp).  Those are the only 2 places
> where this version of longjmp touches ebp.  Is it possible to force a
> stackframe by just adding a suitable attribute to either the setjmp
> function prototype, or the function which calls setjmp?
and we had relevant report in ruby.
http://redmine.ruby-lang.org/issues/5375

Kai, would you mind if i reopen this bug you rejected?
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49230

>
> Bob
>
>


-- 
Regards.