Re: problems with threads/destructors in -current with llvm/clang

From: Mark Atkinson <atkin901_at_gmail.com>
Date: Mon, 10 Dec 2012 13:13:23 -0800
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On 12/10/2012 12:45, Mark Atkinson wrote:
> On 12/10/2012 12:33, Konstantin Belousov wrote:
> 
>> Hmm.  Since I took out -O2 and added -g in rebuilding 
>> libthr/libc/rtld, I figured I needed to reproduce a new
>> segfault, but the rtld side of things seems broken:
>>> Use e.g. cd src/libexec/rtld-elf && make DEBUG_FLAGS=-g clean
>>> all install This is really FAQ.
> 
> 
> It _is_ strange, because I did almost exactly that (dumped a
> temporary DEBUG_FLAGS/CFLAGS in /etc/make.conf)
> 
> The one I had problems with was libc since It needs a make depend
> in there.
> 
> $ readelf -w /libexec/ld-elf.so.1 |head The section .debug_aranges
> contains:
> 
> Length:                   28 Version:                  2 Offset
> into .debug_info:  0 Pointer Size:             4 Segment Size:
> 0
> 
> Address    Length 0x00000e80 0x49 $

So ignoring this weirdness, running under valgrind always segfaults
and the core seems useful.

#0  0x0061bd59 in handle_signal (actp=0xbf9fd490, sig=20,
info=0xbf9fd7b0, ucp=0x0) at /usr/src/lib/libthr/thread/thr_sig.c:198
#1  0x0061b71c in thr_sighandler (sig=20, info=0xbf9fd7b0, _ucp=0x0)
at /usr/src/lib/libthr/thread/thr_sig.c:182
#2  0x380434dc in ?? ()
#3  0x00000014 in ?? ()
#4  0xbf9fd7b0 in ?? ()
#5  0x00000000 in ?? ()
(gdb) frame 0
#0  0x0061bd59 in handle_signal (actp=0xbf9fd490, sig=20,
info=0xbf9fd7b0, ucp=0x0) at /usr/src/lib/libthr/thread/thr_sig.c:198
198             SIGSETOR(actp->sa_mask, ucp->uc_sigmask);
(gdb) list
193             int cancel_enable;
194             int in_sigsuspend;
195             int err;
196
197             /* add previous level mask */
198             SIGSETOR(actp->sa_mask, ucp->uc_sigmask);
199
200             /* add this signal's mask */
201             if (!(actp->sa_flags & SA_NODEFER))
202                     SIGADDSET(actp->sa_mask, sig);

(gdb) p actp
$1 = (struct sigaction *) 0xbf9fd490
(gdb) p *actp
$2 = {__sigaction_u = {__sa_handler = 0x288310
<qt_sa_sigchld_handler(int)>, __sa_sigaction = 0x288310
<qt_sa_sigchld_handler(int)>}, sa_flags = 8, sa_mask = {__bits = {0,
0, 0, 0}}}
(gdb) p *ucp
Cannot access memory at address 0x0
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Received on Mon Dec 10 2012 - 20:13:44 UTC

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