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Date: Wed, 11 Dec 2002 09:27:44 +0100
From: Thomas Pfaff <tpfaff AT gmx DOT net>
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To: Oreste Bernardi <oreste DOT bernardi AT st DOT com>
CC: cygwin AT cygwin DOT com
Subject: Re: SIGSEGV when called sem_init() with gdb.
References: <63340-220021221016341397 AT M2W082 DOT mail2web DOT com> <003e01c2a077$3b065ba0$940782a4 AT agr DOT st DOT com>
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Just add a breakpoint after the sem_init call.
To avoid multiple initializations sem_init checks if the semaphore is 
already initialized and will return EBUSY in that case.
The check is done via IsBadWritePtr which will trigger a SEGV if the 
pointer is invalid and not NULL.
The SEGV is handled internally and will not cause the program to stop.

Thomas

Oreste Bernardi wrote:
> I installed
> gdb                 20020718-1.
> 
> I tried again and I see same behavior.
> 
> By the way, is gdb 20020718-1 experimental version or stable version ?
> 
> Oreste
> 
> 
> ----- Original Message ----- 
> From: <lhall AT pop DOT ma DOT ultranet DOT com>
> To: <oreste DOT bernardi AT st DOT com>; <cygwin AT cygwin DOT com>
> Sent: Tuesday, December 10, 2002 5:03 PM
> Subject: RE: SIGSEGV when called sem_init() with gdb.
> 
> 
> Rerun setup and update your gdb.  If that doesn't help, 
> let the list know.
> 
> Larry
> 
> Original Message:
> -----------------
> From: Oreste Bernardi oreste DOT bernardi AT st DOT com
> Date: Tue, 10 Dec 2002 16:01:16 +0100
> To: cygwin AT cygwin DOT com
> Subject: SIGSEGV when called sem_init() with gdb.
> 
> 
> Dear, all
> 
> #include <semaphore.h>
> int main () {
> int p;
> sem_t sem;
> int i=0,d;
> //sem=(sem_t)NULL; //With this There isn't any problem
> sem_init (&sem,0,1);
> sem_post (&sem);
> sem_wait(&sem);
> return i;
> }
> 
> cygwin 1.3.17-1
> gcc  3.2-3
> gdb  20010428-3
> 
> When executing this source code with gdb I get an SIGSEGV signal  when
> sem_init() function is called.
> If I continue on, program works fine.
> If program is not executed from gdb, it works without any error.
> If I initialize it with NULL, I don't get any error.
> 
> I think that is the same behavior as described by following mail:
> http://sources.redhat.com/ml/cygwin/2002-10/msg00956.html
> Is this true ?
> 
> To avoid annoying gdb error message, is my solution ("sem=(sem_t)NULL")
> reliable and portable ?
> 
> Best Regards
> Oreste Bernardi
> 
> 
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