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Date: Tue, 12 Jul 2011 13:15:09 -0400
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Subject: Re: Pthreads and GDB?
From: Jan Chludzinski <jan DOT chludzinski AT gmail DOT com>
To: cygwin AT cygwin DOT com
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Sorry, I forgot to build with the -g option.

But still as I'm stepping passed the 2 pthread_create() routines they
finish executing before I can set a break.  Why?

---Jan


On Tue, Jul 12, 2011 at 1:02 PM, Jan Chludzinski
<jan DOT chludzinski AT gmail DOT com> wrote:
>> Since cygwin1.dll is multithreaded, I routinely set breakpoints which
>> are only hit in a thread.  So, yes, gdb is supposed to be multi-thread
>> aware.
>
> I have a 2 thread program.  I set the break for main() and run (to main):
>
>      (gdb) b main
>      Breakpoint 1 at 0x401191
>      (gdb) r
>      Starting program: /home/John/projects/pthreads/test1/a.exe
>      [New thread 3680.0x13e8]
>      Error: dll starting at 0x76ff0000 not found.
>      Error: dll starting at 0x76590000 not found.
>      Error: dll starting at 0x76ff0000 not found.
>      Error: dll starting at 0x76c40000 not found.
>      [New thread 3680.0xc7c]
>      Breakpoint 1, 0x00401191 in main ()
>
> Wait a few seconds and start to step:
>
>      (gdb) n
>      Single stepping until exit from function main,
>      which has no line number information.
>      [New thread 3680.0x1410]
>      [New thread 3680.0x1540]
>      Counter value functionCount1: 1
>      Counter value functionCount2: 2
>      ...
>      Final count: 10
>      Program exited normally.
>
> As you can see the threads have finished executing, along with the
> main thread, *before * I ever get a chance to step to the first
> pthread_create().  Let alone set a break in a thread.
>
> Why?
>
> Thanks, Jan
>
> On Tue, Jul 12, 2011 at 6:16 AM, Jan Chludzinski
> <jan DOT chludzinski AT gmail DOT com> wrote:
>> I went to GNU.org to read about GDB and threads since I'm having
>> trouble working with ptheads under GDB on Cygwin.  I notice this on
>> the GNU.org web site:
>>
>> "Warning: These facilities are not yet available on every GDB
>> configuration where the operating system supports threads. If your GDB
>> does not support threads, these commands have no effect. For example,
>> a system without thread support shows no output from `info threads',
>> and always rejects the thread command, like this:"
>>
>> What the level of support for threads with GDB under Cygwin?
>>
>> Switching between threads causes seg-faults.  Also, I thought that
>> while you're stepping through one thread, the other threads weren't
>> running? Shouldn't I be able to set a breakpoint in a thread before
>> pthread_create() is invoked?  Doesn't appear to be the case?
>>
>> ---Jan
>>
>

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