break doesn't work with thread on mips

break doesn't work with thread on mips

[H . J . Lu]

When I do

# gdb a.out
(gdb) b main
Breakpoint 1 at 0x400910: file x.c, line 25.
(gdb) r
(gdb) del 1
(gdb) b main
reading register sp (#29): No such process.

That is break no longer works after the program runs if thread is used.
Why does gdb want to read sp anyway? It sounds like the old bug:

http://sources.redhat.com/ml/gdb/2001-11/msg00156.html

Has it been fixed?


H.J.

Re: break doesn't work with thread on mips

[Michael Snyder]

"H . J . Lu" wrote:
> 
> When I do
> 
> # gdb a.out
> (gdb) b main
> Breakpoint 1 at 0x400910: file x.c, line 25.
> (gdb) r
> (gdb) del 1
> (gdb) b main
> reading register sp (#29): No such process.
> 
> That is break no longer works after the program runs if thread is used.
> Why does gdb want to read sp anyway? 

Probably because it has to analyze the prologue of main, 
to place the breakpoint after the prologue.  Many prologue
analyzers will poke around at the stack.

Re: break doesn't work with thread on mips

[H . J . Lu]

On Wed, Mar 06, 2002 at 05:20:34PM -0800, Michael Snyder wrote:
> "H . J . Lu" wrote:
> > 
> > When I do
> > 
> > # gdb a.out
> > (gdb) b main
> > Breakpoint 1 at 0x400910: file x.c, line 25.
> > (gdb) r
> > (gdb) del 1
> > (gdb) b main
> > reading register sp (#29): No such process.
> > 
> > That is break no longer works after the program runs if thread is used.
> > Why does gdb want to read sp anyway? 
> 
> Probably because it has to analyze the prologue of main, 
> to place the breakpoint after the prologue.  Many prologue
> analyzers will poke around at the stack.

Why does gdb do that? The program has stopped.


H.J.

Re: break doesn't work with thread on mips

[Michael Snyder]

"H . J . Lu" wrote:
> 
> On Wed, Mar 06, 2002 at 05:20:34PM -0800, Michael Snyder wrote:
> > "H . J . Lu" wrote:
> > >
> > > When I do
> > >
> > > # gdb a.out
> > > (gdb) b main
> > > Breakpoint 1 at 0x400910: file x.c, line 25.
> > > (gdb) r
> > > (gdb) del 1
> > > (gdb) b main
> > > reading register sp (#29): No such process.
> > >
> > > That is break no longer works after the program runs if thread is used.
> > > Why does gdb want to read sp anyway?
> >
> > Probably because it has to analyze the prologue of main,
> > to place the breakpoint after the prologue.  Many prologue
> > analyzers will poke around at the stack.
> 
> Why does gdb do that? The program has stopped.

You gave it a symbol, "main".  It knows that you don't really want
to set a breakpoint at the address corresponding to that symbol
(the label or entry-point of main), but instead you would really
like to set a breakpoint at the first instruction after the prologue
of main.  It's not really useful to set a breakpoint before that.

The fact that you happen to be sitting at that exact address is
irrelevant -- gdb doesn't know that.

Re: break doesn't work with thread on mips

[H . J . Lu]

On Wed, Mar 06, 2002 at 05:26:46PM -0800, Michael Snyder wrote:
> "H . J . Lu" wrote:
> > 
> > On Wed, Mar 06, 2002 at 05:20:34PM -0800, Michael Snyder wrote:
> > > "H . J . Lu" wrote:
> > > >
> > > > When I do
> > > >
> > > > # gdb a.out
> > > > (gdb) b main
> > > > Breakpoint 1 at 0x400910: file x.c, line 25.
> > > > (gdb) r
> > > > (gdb) del 1
> > > > (gdb) b main
> > > > reading register sp (#29): No such process.
> > > >
> > > > That is break no longer works after the program runs if thread is used.
> > > > Why does gdb want to read sp anyway?
> > >
> > > Probably because it has to analyze the prologue of main,
> > > to place the breakpoint after the prologue.  Many prologue
> > > analyzers will poke around at the stack.
> > 
> > Why does gdb do that? The program has stopped.
> 
> You gave it a symbol, "main".  It knows that you don't really want
> to set a breakpoint at the address corresponding to that symbol
> (the label or entry-point of main), but instead you would really
> like to set a breakpoint at the first instruction after the prologue
> of main.  It's not really useful to set a breakpoint before that.
> 
> The fact that you happen to be sitting at that exact address is
> irrelevant -- gdb doesn't know that.

My question is why gdb pokes a dead process. There is nothing to
poke with. FYI, it only happens with thread.


H.J.

Re: break doesn't work with thread on mips

[Michael Snyder]

"H . J . Lu" wrote:
> 
> On Wed, Mar 06, 2002 at 05:26:46PM -0800, Michael Snyder wrote:
> > "H . J . Lu" wrote:
> > >
> > > On Wed, Mar 06, 2002 at 05:20:34PM -0800, Michael Snyder wrote:
> > > > "H . J . Lu" wrote:
> > > > >
> > > > > When I do
> > > > >
> > > > > # gdb a.out
> > > > > (gdb) b main
> > > > > Breakpoint 1 at 0x400910: file x.c, line 25.
> > > > > (gdb) r
> > > > > (gdb) del 1
> > > > > (gdb) b main
> > > > > reading register sp (#29): No such process.
> > > > >
> > > > > That is break no longer works after the program runs if thread is used.
> > > > > Why does gdb want to read sp anyway?
> > > >
> > > > Probably because it has to analyze the prologue of main,
> > > > to place the breakpoint after the prologue.  Many prologue
> > > > analyzers will poke around at the stack.
> > >
> > > Why does gdb do that? The program has stopped.
> >
> > You gave it a symbol, "main".  It knows that you don't really want
> > to set a breakpoint at the address corresponding to that symbol
> > (the label or entry-point of main), but instead you would really
> > like to set a breakpoint at the first instruction after the prologue
> > of main.  It's not really useful to set a breakpoint before that.
> >
> > The fact that you happen to be sitting at that exact address is
> > irrelevant -- gdb doesn't know that.
> 
> My question is why gdb pokes a dead process. There is nothing to
> poke with. FYI, it only happens with thread.

Oh.  Well, from the log you've shown above, I don't see 
any indication that the process is dead.  Why is it dead?
How does gdb know that it's dead?

Re: break doesn't work with thread on mips

[Daniel Jacobowitz]

On Wed, Mar 06, 2002 at 01:05:00AM -0800, H . J . Lu wrote:
> When I do
> 
> # gdb a.out
> (gdb) b main
> Breakpoint 1 at 0x400910: file x.c, line 25.
> (gdb) r
> (gdb) del 1
> (gdb) b main
> reading register sp (#29): No such process.
> 
> That is break no longer works after the program runs if thread is used.
> Why does gdb want to read sp anyway? It sounds like the old bug:
> 
> http://sources.redhat.com/ml/gdb/2001-11/msg00156.html
> 
> Has it been fixed?

Are you using current GDB?

Program exited normally.
(gdb) del 1
(gdb) b main
Breakpoint 2 at 0x4009f4: file twothreads.c, line 16.


It works for me.

-- 
Daniel Jacobowitz                           Carnegie Mellon University
MontaVista Software                         Debian GNU/Linux Developer

Re: break doesn't work with thread on mips

[H . J . Lu]

On Wed, Mar 06, 2002 at 10:35:07PM -0500, Daniel Jacobowitz wrote:
> On Wed, Mar 06, 2002 at 01:05:00AM -0800, H . J . Lu wrote:
> > When I do
> > 
> > # gdb a.out
> > (gdb) b main
> > Breakpoint 1 at 0x400910: file x.c, line 25.
> > (gdb) r
> > (gdb) del 1
> > (gdb) b main
> > reading register sp (#29): No such process.
> > 
> > That is break no longer works after the program runs if thread is used.
> > Why does gdb want to read sp anyway? It sounds like the old bug:
> > 
> > http://sources.redhat.com/ml/gdb/2001-11/msg00156.html
> > 
> > Has it been fixed?
> 
> Are you using current GDB?
> 
> Program exited normally.
> (gdb) del 1
> (gdb) b main
> Breakpoint 2 at 0x4009f4: file twothreads.c, line 16.
> 

It seems fixed in 5.2.


H.J.