List command question

List command question

[Manoj Iyer]

List command has different out put when the program is compiled with -g
option and when it is not...

I checked out the lastest CVS head of GDB and wrote a small hello world
program, comppiled it with and without -g on a PowerPC 64bit machine, and
here is the diff in output.

manjo@nefertiti:~/projects/src> cc -o ~/tests/test ~/tests/test.c
manjo@nefertiti:~/projects/src> ./gdb/gdb ~/tests/test
GNU gdb 2004-04-17-cvs
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you
are
welcome to change it and/or distribute copies of it under certain
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for
details.
This GDB was configured as "powerpc64-gnu-linux"...Using host libthread_db
libra
ry "/lib64/tls/libthread_db.so.1".

(gdb) list
1       ../sysdeps/powerpc/powerpc32/elf/start.S: No such file or
directory.
        in ../sysdeps/powerpc/powerpc32/elf/start.S
(gdb) quit




manjo@nefertiti:~/projects/src> cc -g -o ~/tests/test ~/tests/test.c
manjo@nefertiti:~/projects/src> ./gdb/gdb ~/tests/test
GNU gdb 2004-04-17-cvs
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you
are
welcome to change it and/or distribute copies of it under certain
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for
details.
This GDB was configured as "powerpc64-gnu-linux"...Using host libthread_db
libra
ry "/lib64/tls/libthread_db.so.1".

(gdb) list
1       #include <stdio.h>
2
3       main()
4       {
5           printf("hello world\n");
6       }
7
(gdb)


I am not sure how the list command should look like when no "-g" is used
to compile the test. Any suggestion? comments??


Thanks
Manoj Iyer

Re: List command question

[Andreas Schwab]

Manoj Iyer <manjo@austin.ibm.com> writes:

> I am not sure how the list command should look like when no "-g" is used
> to compile the test. Any suggestion? comments??

You can't expect meaningful results without debugging information as
nothing else is providing information about source files.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux AG, Maxfeldstraße 5, 90409 Nürnberg, Germany
Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

RE: List command question

[Monika Chaddha]

Hi Manoj

I m not sure but according to my knowledge, whenever we compile any
program with -g option, the compiler generates some debugging
information, which also includes the path of source file. Without
debugging information, it's not possible to use GDB and surely we will
get unexpected results from GDB

Monika



>-----Original Message-----
>From: gdb-owner@sources.redhat.com
[mailto:gdb-owner@sources.redhat.com] On
>Behalf Of Manoj Iyer
>Sent: Friday, May 14, 2004 11:44 PM
>To: gdb@sources.redhat.com
>Subject: List command question
>
>
>List command has different out put when the program is compiled with -g
>option and when it is not...
>
>I checked out the lastest CVS head of GDB and wrote a small hello world
>program, comppiled it with and without -g on a PowerPC 64bit machine,
and
>here is the diff in output.
>
>manjo@nefertiti:~/projects/src> cc -o ~/tests/test ~/tests/test.c
>manjo@nefertiti:~/projects/src> ./gdb/gdb ~/tests/test
>GNU gdb 2004-04-17-cvs
>Copyright 2004 Free Software Foundation, Inc.
>GDB is free software, covered by the GNU General Public License, and
you
>are
>welcome to change it and/or distribute copies of it under certain
>conditions.
>Type "show copying" to see the conditions.
>There is absolutely no warranty for GDB.  Type "show warranty" for
>details.
>This GDB was configured as "powerpc64-gnu-linux"...Using host
libthread_db
>libra
>ry "/lib64/tls/libthread_db.so.1".
>
>(gdb) list
>1       ../sysdeps/powerpc/powerpc32/elf/start.S: No such file or
>directory.
>        in ../sysdeps/powerpc/powerpc32/elf/start.S
>(gdb) quit
>
>
>
>
>manjo@nefertiti:~/projects/src> cc -g -o ~/tests/test ~/tests/test.c
>manjo@nefertiti:~/projects/src> ./gdb/gdb ~/tests/test
>GNU gdb 2004-04-17-cvs
>Copyright 2004 Free Software Foundation, Inc.
>GDB is free software, covered by the GNU General Public License, and
you
>are
>welcome to change it and/or distribute copies of it under certain
>conditions.
>Type "show copying" to see the conditions.
>There is absolutely no warranty for GDB.  Type "show warranty" for
>details.
>This GDB was configured as "powerpc64-gnu-linux"...Using host
libthread_db
>libra
>ry "/lib64/tls/libthread_db.so.1".
>
>(gdb) list
>1       #include <stdio.h>
>2
>3       main()
>4       {
>5           printf("hello world\n");
>6       }
>7
>(gdb)
>
>
>I am not sure how the list command should look like when no "-g" is
used
>to compile the test. Any suggestion? comments??
>
>
>Thanks
>Manoj Iyer

Re: List command question

[Eli Zaretskii]

> From: Andreas Schwab <schwab@suse.de>
> Date: Fri, 14 May 2004 21:27:18 +0200
> 
> You can't expect meaningful results without debugging information as
> nothing else is providing information about source files.

I tried this with GDB 6.1 and the DJGPP toolchain, and GDB said "(no
debugging symbols found)", which is reasonable, IMHO.

Why didn't it do so in Manoj's case?

Re: List command question

[Andreas Schwab]

"Eli Zaretskii" <eliz@gnu.org> writes:

>> From: Andreas Schwab <schwab@suse.de>
>> Date: Fri, 14 May 2004 21:27:18 +0200
>> 
>> You can't expect meaningful results without debugging information as
>> nothing else is providing information about source files.
>
> I tried this with GDB 6.1 and the DJGPP toolchain, and GDB said "(no
> debugging symbols found)", which is reasonable, IMHO.
>
> Why didn't it do so in Manoj's case?

Because there is _some_ debugging info, presumably from libc.  And once
gdb has found any debugging info at all it will not say "(no debugging
symbols found)" any more, even if more objects without debugging info are
crossed.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux AG, Maxfeldstraße 5, 90409 Nürnberg, Germany
Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: List command question

[Ramana Radhakrishnan]

Thus spake Eli Zaretskii
>> From: Andreas Schwab <schwab@suse.de>
>> Date: Fri, 14 May 2004 21:27:18 +0200
>>
>> You can't expect meaningful results without debugging information as
>> nothing else is providing information about source files.
>
> I tried this with GDB 6.1 and the DJGPP toolchain, and GDB said "(no
> debugging symbols found)", which is reasonable, IMHO.
>
> Why didn't it do so in Manoj's case?

Is it possible that bis start.S is alone compiled with debug info in such
a case  ? Would that be a valid enough reason for this to happen  ? But
isnt it strange that it can find just one file even if libc was compiled
with debug info ?




cheers
Ramana


>


----
Ramana Radhakrishnan
Codito Technologies

RE: List command question

[Manoj Iyer]

> >manjo@nefertiti:~/projects/src> cc -o ~/tests/test ~/tests/test.c
> >manjo@nefertiti:~/projects/src> ./gdb/gdb ~/tests/test
> >GNU gdb 2004-04-17-cvs
> >Copyright 2004 Free Software Foundation, Inc.
> >GDB is free software, covered by the GNU General Public License, and
> you
> >are
> >welcome to change it and/or distribute copies of it under certain
> >conditions.
> >Type "show copying" to see the conditions.
> >There is absolutely no warranty for GDB.  Type "show warranty" for
> >details.
> >This GDB was configured as "powerpc64-gnu-linux"...Using host
> libthread_db
> >libra
> >ry "/lib64/tls/libthread_db.so.1".
> >
> >(gdb) list
> >1       ../sysdeps/powerpc/powerpc32/elf/start.S: No such file or
> >directory.
> >        in ../sysdeps/powerpc/powerpc32/elf/start.S
> >(gdb) quit
> >
> >

IMHO this output is simply misleading, it should print something
meaningful, like no symbols found, or no debug info in executable, or
compile with -g to generate more debug info etc.... 'file not found' is
not a clear indicator of what is going on.

--
Manoj Iyer

Re: List command question

[Andrew Cagney]

>>>> >manjo@nefertiti:~/projects/src> cc -o ~/tests/test ~/tests/test.c
>>>> >manjo@nefertiti:~/projects/src> ./gdb/gdb ~/tests/test
>>>> >GNU gdb 2004-04-17-cvs
>>>> >Copyright 2004 Free Software Foundation, Inc.
>>>> >GDB is free software, covered by the GNU General Public License, and
>>
>>> you
>>
>>>> >are
>>>> >welcome to change it and/or distribute copies of it under certain
>>>> >conditions.
>>>> >Type "show copying" to see the conditions.
>>>> >There is absolutely no warranty for GDB.  Type "show warranty" for
>>>> >details.
>>>> >This GDB was configured as "powerpc64-gnu-linux"...Using host
>>
>>> libthread_db
>>
>>>> >libra
>>>> >ry "/lib64/tls/libthread_db.so.1".
>>>> >
>>>> >(gdb) list
>>>> >1       ../sysdeps/powerpc/powerpc32/elf/start.S: No such file or
>>>> >directory.
>>>> >        in ../sysdeps/powerpc/powerpc32/elf/start.S
>>>> >(gdb) quit
>>>> >
>>>> >
> 
> 
> IMHO this output is simply misleading, it should print something
> meaningful, like no symbols found, or no debug info in executable, or
> compile with -g to generate more debug info etc.... 'file not found' is
> not a clear indicator of what is going on.

As others pointed out, the above is correct.  It found debug information 
for ``entry-point'' and then tried to use it.  Only to barf because the 
the corresponding source files were not installed.  There's not much GDB 
can do when a user's program contains debug info but is missing the 
corresponding source.

What happens if you enter:

	(gdb) list main

Andrew

Re: List command question

[Manoj Iyer]

> As others pointed out, the above is correct.  It found debug information
> for ``entry-point'' and then tried to use it.  Only to barf because the
> the corresponding source files were not installed.  There's not much GDB
> can do when a user's program contains debug info but is missing the
> corresponding source.
>
> What happens if you enter:
>
> 	(gdb) list main
>
> Andrew
>

I get no line number known for main...

manjo@nefertiti:~/tests> gdb64 hellow1
GNU gdb 6.1
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you
are
welcome to change it and/or distribute copies of it under certain
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for
details.
This GDB was configured as "ppc64-suse-linux"...Using host libthread_db
library "/lib64/tls/libthread_db.so.1".

(gdb) list
1       ../sysdeps/powerpc/powerpc64/elf/start.S: No such file or
directory.
        in ../sysdeps/powerpc/powerpc64/elf/start.S
(gdb) list main
No line number known for main.
(gdb)


But for a C program I get the following...

manjo@nefertiti:~/tests> gdb64 ./test1
GNU gdb 6.1
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you
are
welcome to change it and/or distribute copies of it under certain
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for
details.
This GDB was configured as "ppc64-suse-linux"...Using host libthread_db
library "/lib64/tls/libthread_db.so.1".

(gdb) list main
1       #include <stdio.h>
2
3       main()
4       {
5           printf("hello world\n");
6       }
7
(gdb)

Re: List command question

[Andrew Cagney]

> I get no line number known for main...
> 
> manjo@nefertiti:~/tests> gdb64 hellow1
> GNU gdb 6.1
> Copyright 2004 Free Software Foundation, Inc.
> GDB is free software, covered by the GNU General Public License, and you
> are
> welcome to change it and/or distribute copies of it under certain
> conditions.
> Type "show copying" to see the conditions.
> There is absolutely no warranty for GDB.  Type "show warranty" for
> details.
> This GDB was configured as "ppc64-suse-linux"...Using host libthread_db
> library "/lib64/tls/libthread_db.so.1".
> 
> (gdb) list
> 1       ../sysdeps/powerpc/powerpc64/elf/start.S: No such file or
> directory.
>         in ../sysdeps/powerpc/powerpc64/elf/start.S
> (gdb) list main
> No line number known for main.
> (gdb)

GDB has the concept of a current source-and-line (SAL).  When GDB starts 
it initializes it to something.  Looking at the behavior you've 
illustrated, it tries in order: main's SAL; entry-point's SAL; ???

I guess the question is, should GDB set SAL to main when main doesn't 
have any line number information?

Note here that this will end up interacting with the ``start'' mechanism 
that Joel is playing with - its a mechanism for doing run-to ``main''. 
So this will be a language dependent concept.

Andrew