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 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

finish implementation

[Smita]

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

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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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
 > >

Re: libgdb

[Stan Shebs]

Matthew Hall wrote:
> I've seen references to a libgdb project.
>   
An idea left over from ancient days, never got off the ground. The 
theory was that one could link it into both the traditional command-line 
frontend and into various GUIs. Lots of technical difficulties, two 
chief ones being that 1) it would have had to be a very "wide" API in 
order to be sufficient to cover all of GDB functionality, and 2) the 
library would have to be able to hand control back to the UI on demand, 
difficult when inferior control uses blocking system calls. In practice, 
it seems to work well enough to have the GUI be a separate program that 
communicates with GDB, whether via command line or MI (machine 
interface) syntax, and there is some advantage to the "firewalling" 
inherent in a two-program scheme, so there's not much motivation to do a 
libgdb anymore.

Stan

Re: libgdb

[Daniel Jacobowitz]

On Fri, Nov 02, 2007 at 04:45:45PM +0000, Matthew Hall wrote:
> I've seen references to a libgdb project.
> Can anyone tell me if libgdb is still active?

No.

> Is it complete?

No.

> Is it used internally by gdb itself?

No clear answer to this.  There was a "libgdb interface"; some bits of
GDB use it, other bits do not.  It's all linked in together.

-- 
Daniel Jacobowitz
CodeSourcery

libgdb

[Matthew Hall]

I've seen references to a libgdb project.
Can anyone tell me if libgdb is still active?
Is it complete?
Is it used internally by gdb itself?

Thanks for any info or links to useful documentation.

libgdb

[jacques]

Hello,
I'm currently working on a new debugger, and I want to base it on 
libgdb. However, finding documentation about libgdb, or even finding 
libgdb itself, has proved a daunting task. My understanding is that 
libgdb is simply a library containing all the high level functions of 
gdb, but let's me call them inside my code. Is libgdb rebuilt everytime 
a new gdb comes out? where can i find more information about 
libgdb(google gives me 2 manuals, both very very sparse on any 
information), and where would I get the latest libgdb?
--Jacques

Re: libgdb

[Joel Brobecker]

> 1) Invoke GDB and parse the command line (emacs does this)
> 2) Invoke GDB's MI interpreter and write yourself an MI parser (Eclipse 
> and Apple's tools for MacOS X do this)
> 3) Write your GUI using GDB's hooks and events (Insight does this)
> 
> Obviously, #2 is the most desirably way to isolate yourselves from GDB 
> changes. Unfortunately, MI is still a work in progress. (Of course, I'm 
> still partial to #3 for speed.. ;-)

One advantage of method #1 or #2, used by GVD, is that GDB is a separate
process. This GDB process does not need to run on the same host as GVD.
Even if I'm debugging on a distant machine, I can run GVD on my local
machine, reducing tremendously the network traffic. Given that I live in
the west coast, and that most machines I work on are located in NY and
Paris, this is a definite plus.

I think GVD uses method #1, but I would recommend method #2 as the
output is most probably easier to parse.

-- 
Joel

Re: libgdb

[Keith Seitz]

On Fri, 22 Nov 2002 a2782@dis.ulpgc.es wrote:

> I am involved in a project of making a educational graphic interface 
> and we are thinking about putting it over GDB. My question is: Has 
> anybody worked with libgdb? My first approximation is invoking gdb as 
> Emacs does, but using libgdb. I hope someone has worked with libgdb and 
> can help and advise me.

Sadly, libgdb is a pipedream, and still quite a ways off (but it's 
getting closer almost every day).

There are three ways to commonly interface some sort of GUI application 
top of GDB:

1) Invoke GDB and parse the command line (emacs does this)
2) Invoke GDB's MI interpreter and write yourself an MI parser (Eclipse 
and Apple's tools for MacOS X do this)
3) Write your GUI using GDB's hooks and events (Insight does this)

Obviously, #2 is the most desirably way to isolate yourselves from GDB 
changes. Unfortunately, MI is still a work in progress. (Of course, I'm 
still partial to #3 for speed.. ;-)

Keith

libgdb

[a2782]

Hi to all!

I am involved in a project of making a educational graphic interface 
and we are thinking about putting it over GDB. My question is: Has 
anybody worked with libgdb? My first approximation is invoking gdb as 
Emacs does, but using libgdb. I hope someone has worked with libgdb and 
can help and advise me.

Thanks in advance!

libgdb

[Satya]

Hi,
  I am new to libgdb.Can some one tell me how I can use libgdb to
construct an object containing the result of the gdb command.

Thanks,
Satya