gdb refuses to 'break'

gdb refuses to 'break'

[Markus Brandner]

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Hi!

Either I missed the point when reading the gdb documentation or
I'm just experiencing some strange behaviour in gdb.
Im running a Slackware 8.1 system on kernel 2.4.18 with
libc-2.2.5

When I compile the following code:

test.c:
#include <stdio.h>

int main(int argc, char **argv)
{
	printf("Breakpoint test\n");
	return 0;
}

using "gcc -g test.c -o test" (my gcc is 2.95.3)
and try to set a break-point with gdb 5.2:

(gdb) break main
Breakpoint 1 at 0x80483f6: file test.c, line 5.
(gdb) run
Starting program: /home/home_PCs105/brandner/tmp/test 
Breakpoint test

Program exited normally.
You can't do that without a process to debug.
(gdb) 

gdb seems to run straight through ignoring the break.
I tried break: line number - same result
I even get the same results using gdb 5.3.

However, compiling the same source using the same gcc
on a libc-2.2.3 machine (kernel 2.2.21) and trying to
do the same thing using gdb 5.0 works perfectly
(but not with any more recent gdb version)

What am I missing?

Thanks for your help,

Markus
- -- 
- -----------------------------------------------------------------
Markus Brandner               Institute of Electrical Measurement
                                and Measurement Signal Processing
phone: +43 316 873 7773             Graz University of Technology
fax:   +43 316 873 4279                     Schiessstattgasse 14B
email: brandner@emt.tugraz.at                 A8010 Graz, Austria
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return type of a fucntion

[Smita]

Hi,
When I print $r3 on returning from a function, I get the return value. But
is there a way to get the type of the return value (eg. whether it is a
pointer or an interger)??

Thanks!
Smita

gdb's communication to a process/libgdb?

[Smita]

Hi,
 I am spawing a gdb process from my process and feeding to gdb an input
script.
I want the parent process to be able to control this gdb process. For this
to happen, I want to communicate to the parent process that a breakpoint
has occurred when gdb stops at a breakpoint? Is it possible to to this?
There is something called libgdb. I am not sure if that can be used for
this purpose.

Any feedback on this would be greatly appreciated.
Thanks
Smita

Re: gdb's communication to a process/libgdb?

[Daniel Jacobowitz]

On Wed, Apr 16, 2003 at 12:59:14PM -0700, Smita wrote:
> Hi,
>  I am spawing a gdb process from my process and feeding to gdb an input
> script.
> I want the parent process to be able to control this gdb process. For this
> to happen, I want to communicate to the parent process that a breakpoint
> has occurred when gdb stops at a breakpoint? Is it possible to to this?
> There is something called libgdb. I am not sure if that can be used for
> this purpose.
> 
> Any feedback on this would be greatly appreciated.

You should probably be reading the documentation for "MI".  Check the
manual, available online under http://sources.redhat.com/gdb/.

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer

libgdb

[Smita]

Hi,
 I am new to libgdb. Could someone please give me a pointer to its usage
documentaion?
Thanks
Smita

is libgdb okay to use?

[Smita]

Hi,
 I read somewhere that libgdb project was scrapped. Is that true?

Thanks
Smita

Re: libgdb

[Elena Zannoni]

Smita writes:
 > Hi,
 >  I am new to libgdb. Could someone please give me a pointer to its usage
 > documentaion?
 > Thanks
 > Smita
 > 


http://sources.redhat.com/gdb/current/onlinedocs/gdb_25.html#SEC207

Re: libgdb

[Smita]

Where can I get libgdb from?

Thanks!
Smita

On Wed, 16 Apr 2003, Elena Zannoni wrote:

> Smita writes:
>  > Hi,
>  >  I am new to libgdb. Could someone please give me a pointer to its usage
>  > documentaion?
>  > Thanks
>  > Smita
>  >
>
>
> http://sources.redhat.com/gdb/current/onlinedocs/gdb_25.html#SEC207
>

finish implementation

[Smita]

Hi,
 How is finish implemented? Is it an internal breakpoint for gdb which is
not visible to user?

Thanks
Smita

Re: libgdb

[Elena Zannoni]

Smita writes:
 > Where can I get libgdb from?
 > 

there is no libgdb entity per se. The Mi interface is included with the
regular gdb sources.

 > Thanks!
 > Smita
 > 
 > On Wed, 16 Apr 2003, Elena Zannoni wrote:
 > 
 > > Smita writes:
 > >  > Hi,
 > >  >  I am new to libgdb. Could someone please give me a pointer to its usage
 > >  > documentaion?
 > >  > Thanks
 > >  > Smita
 > >  >
 > >
 > >
 > > http://sources.redhat.com/gdb/current/onlinedocs/gdb_25.html#SEC207
 > >

finish for nested function calls

[Smita]

Hi,
 What is the expected behavior of finish when it is called from multiple
nested funtions?
e.g:
f1() calls f2():
f1()
{
  f2()
}

i do this in gdb:
b f1
finish
end
b f2
finish
end

finish takes effect only for f2() (the innermost function)
So, I get return value from f2() and gdb stops after it returns from f2().
I don't get the return value for f1().
Is that the expected beahvior?

Thanks
Smita

Re: return type of a fucntion

[Peter Barada]

>Hi,
>When I print $r3 on returning from a function, I get the return value. But
>is there a way to get the type of the return value (eg. whether it is a
>pointer or an interger)??

If you know which function you're in, you could always 'ptype
functionName' where 'fuctionName' is replaced with the function's name
and you'll see the type that the function returns. Then you could cast
$r3 to that type.  Of course this doesn't works so well with
float/double as well as structures.

-- 
Peter Barada
peter@baradas.org

Re: gdb refuses to 'break'

[Markus Brandner]

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On Wednesday 16 April 2003 20:17, you wrote:

[...]

> gdb seems to run straight through ignoring the break.
> I tried break: line number - same result
> I even get the same results using gdb 5.3.

This issue is resolved.
The no-'break' problem was not at all related to gdb :)
I ran the test on different machines - every single on (except
the one with the 2.2.21 kernel) having installed the no-ptrace 
kernel patch!

Markus
- -- 
- -----------------------------------------------------------------
Markus Brandner               Institute of Electrical Measurement
                                and Measurement Signal Processing
phone: +43 316 873 7773             Graz University of Technology
fax:   +43 316 873 4279                     Schiessstattgasse 14B
email: brandner@emt.tugraz.at                 A8010 Graz, Austria
- -----------------------------------------------------------------
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