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Date:	Fri, 16 Aug 2013 12:13:01 +0300
From:	Eli Zaretskii <eliz AT gnu DOT org>
Subject:	Re: 64-bit emacs crashes a lot
In-reply-to:	<520DBFCD.4080808@cs.utoronto.ca>
To:	Ryan Johnson <ryan DOT johnson AT cs DOT utoronto DOT ca>
Cc:	cygwin AT cygwin DOT com
Reply-to:	Eli Zaretskii <eliz AT gnu DOT org>
Message-id:	<8338qangma.fsf@gnu.org>
References:	<51F3151D DOT 7040000 AT cs DOT utoronto DOT ca> <51F33565 DOT 1090406 AT cornell DOT edu> <51F33F52 DOT 4060405 AT cs DOT utoronto DOT ca> <51FB1D9E DOT 5090102 AT cs DOT utoronto DOT ca> <20130802080211 DOT GA18054 AT calimero DOT vinschen DOT de> <51FB9228 DOT 2020309 AT cornell DOT edu> <51FBA100 DOT 90005 AT cs DOT utoronto DOT ca> <51FD5462 DOT 5020400 AT cs DOT utoronto DOT ca> <51FFBDFF DOT 7040501 AT cornell DOT edu> <51FFC4F2 DOT 8080909 AT cs DOT utoronto DOT ca> <5203D89E DOT 6030801 AT cornell DOT edu> <5203DCCA DOT 1010105 AT cs DOT utoronto DOT ca> <5205B364 DOT 8090007 AT cs DOT utoronto DOT ca> <52064730 DOT 50404 AT cornell DOT edu> <"52065B3C DOT 6060104 AT cs DOT utoronto <520CCA41.3000107"@cs.utoronto.ca> <520D089A DOT 1020806 AT cornell DOT edu> <83ioz6op5v DOT fsf AT gnu DOT org> <520D4036 DOT 8010303 AT cs DOT utoronto DOT ca> <520D900A DOT 8000907 AT cornell DOT edu> <520DABDC DOT 8020304 AT cs DOT utoronto DOT ca> <520DBFCD DOT 4080808 AT cs DOT utoronto DOT ca>

Please move this discussion to emacs-devel AT gnu DOT org.

> Date: Fri, 16 Aug 2013 01:59:41 -0400
> From: Ryan Johnson <ryan DOT johnson AT cs DOT utoronto DOT ca>
> 
> The variable pending_exact has value 0x0, which would be a Bad Thing... 
> except that the code looks like this:
> >           if (!pending_exact
> >
> >               /* If last exactn not at current position.  */
> > =>            || pending_exact + *pending_exact + 1 != b
> >
> ... with corresponding assembly code looking very reasonable:
> >    0x0000000100535cfa <regex_compile+34482>:    cmpq   $0x0,0x3f8(%rbp)
> >    0x0000000100535d02 <regex_compile+34490>:    je 0x100535eca 
> > <regex_compile+34946>
> >    0x0000000100535d08 <regex_compile+34496>:    mov 0x3f8(%rbp),%rax
> > => 0x0000000100535d0f <regex_compile+34503>:    movzbl (%rax),%eax
> >    0x0000000100535d12 <regex_compile+34506>:    movzbl %al,%eax
> >    0x0000000100535d15 <regex_compile+34509>:    lea 0x1(%rax),%rdx
> >    0x0000000100535d19 <regex_compile+34513>:    mov 0x3f8(%rbp),%rax
> >    0x0000000100535d20 <regex_compile+34520>:    add %rdx,%rax
> >    0x0000000100535d23 <regex_compile+34523>:    cmp %rbx,%rax
> >    0x0000000100535d26 <regex_compile+34526>:    jne 0x100535eca 
> > <regex_compile+34946>

What is the value in the RAX register at the point of the crash?  Is
it also zero?  Or maybe it is some other invalid pointer value?

> A third crash:
> > #1  0x0000000100541930 in re_match_2_internal (bufp=0x10095ce20 
> > <searchbufs+2912>, string1=0x0, size1=0, string2=0x6fffff00028 "-*- 
> > mode: compilation; default-directory: \"~/\" -*-\nCompilation started 
> > at Fri Aug 16 01:32:19\n\nls\n#message-20130808-090732#\t 
> > emacs-crash.txt\t\tmusic\n6b8ob06a.default.tar.xz\t\t 
> > emacs-nox.exe."..., size2=355, pos=254, regs=0x10095def0 
> > <search_regs>, stop=317) at regex.c:6217
> > 6217              abort ();
> This time, p (the subject of the case statement) points to 0x76b3b6c7, 
> which is the middle of a function (ntdll!RtlFillMemory, though the 
> memory map places that address smack in the middle of kernel32.dll 
> instead). This time it makes perfect sense that the switch statement 
> should fail, but how did p go so wrong?

What is bufp->buffer at this point, and what is its contents?

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