Re: Debugging issue with gdbserver and a daemon on the target

Laszlo Papp
2014-08-20T09:10:05Z

On Wed, Aug 20, 2014 at 9:39 AM, Laszlo Papp <lpapp@kde.org> wrote:
> On Wed, Aug 20, 2014 at 9:36 AM, Laszlo Papp <lpapp@kde.org> wrote:
>> On Wed, Aug 20, 2014 at 9:25 AM, Laszlo Papp <lpapp@kde.org> wrote:
>>> On Wed, Aug 20, 2014 at 9:17 AM, Pedro Alves <palves@redhat.com> wrote:
>>>> On 08/19/2014 07:01 PM, Laszlo Papp wrote:
>>>>
>>>>> Hmm, it seems that the stripped binary on the target and the one on
>>>>> the host were out-of-sync. This is really strange since I have not
>>>>> changed the source code. Seems different compilations still can get
>>>>> out-of-sync for the same code so that when I rebuild the same source
>>>>> code, I always need to update the binary on the target, too?
>>>>
>>>> Ideally, if you used the exact same inputs, and the exact same tools,
>>>> and the same exact same tool options, the output is the same. You
>>>> can check that with md5sum, or some such.
>>>
>>> Thanks. I will check that next time.
>>>
>>>>> Anyway, now I only have problems with finding the sources file to view
>>>>> them in cgdb. I do not know why it is wrong, but it seems to be. As
>>>>> you can see the paths are set up for dwarf correctly:
>>>>>
>>>>> /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/meh
>>>>>
>>>>> ... yet, gdb says src/bar.c cannot be found even though it should be
>>>>> in the aforementioned
>>>>> /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/meh
>>>>> path, provided my sysroot setting is good above, but if that was not
>>>>> good, it would not load the binaries anyway, right?
>>>>
>>>> Correct.
>>>
>>> Thanks.
>>>
>>>>> So, if I set that
>>>>> path one line above with the "-d" option to gdb, then the source file
>>>>> can be viewed. What may be going on here?
>>>>
>>>> That sounds like the expected behavior, as the source directory knobs
>>>> are independent from the sysroot setting. See:
>>>>
>>>> https://sourceware.org/gdb/current/onlinedocs/gdb/Source-Path.html
>>>
>>> Heh, coincidentally I started my day with reading that before, but
>>> thanks. At least, it is a confirmation that I am on the right track.
>>> :)
>>>
>>>>> Thanks in advance. I am so desperately lost. :(
>>>>
>>>> I think I'm lost on which part you are lost. :-)
>>>
>>> Well, I am not sure why it does not work. Yocto generates the images
>>> for me, but that is not important here as long as the dwarf
>>> information looks correct after its operation in the provided readelf
>>> output. So, provided that the dwarf information looks correct, and the
>>> files are there, I am not sure why gdb cannot find src/bar.c in
>>> .../git/meh (path above). I will check "show directories" what gdb
>>> sees in my case, but if that does not help, I am not sure how to make
>>> it work. Got a clue?
>>
>> It seems to just show the default:
>>
>> (gdb) show directories
>> Source directories searched: $cdir:$cwd
>> (gdb) show substitute-path
>> List of all source path substitution rules:
>> (gdb)
>>
>> To be detailed, this is the path to the source file in question:
>>
>> -> ./tmp/work/foo-foo-linux-gnueabi/foo-core-image-dbg/1.0-r0/rootfs/usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/foo/foo.c
>>
>> This is where gdb says:
>>
>> (gdb) c
>> Continuing.
>>
>> Breakpoint 1, foo (sp=0x5e968) at foo.c:99
>> 99 foo.c: No such file or directory.
>> (gdb) n
>> 100 in foo.c
>> (gdb)
>>
>> Readelf says again:
>>
>> -> e.g. /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/foo
>>
>> As you can see the two paths differ in
>> "./tmp/work/foo-foo-linux-gnueabi/foo-core-image-dbg/1.0-r0/rootfs",
>> but that is set as sysroot when I run gdb. Do I also need to set this
>> as a substitute path, too, then?
>
> Oh, and more thing to provide as much information as possible to you:
>
> (gdb) info source
> Current source file is foo.c
> Compilation directory is
> /usr/src/debug/foo-git/AUTOINC+0c2cbe33e653afa335ca25156d293552001228fa-r0/git/foo
> Source language is c.
> Compiled with DWARF 2 debugging format.
> Does not include preprocessor macro info.
> (gdb)

This made it work, but is it the best thing to do?

-ex "set substitute-path /usr/src/debug/
./tmp/work/foo-foo-linux-gnueabi/foo-core-image-dbg/1.0-r0/rootfs/usr/src/debug/"

Also, can someone verify that it is also supposed to work if I just
use directories as claimed in here? I cannot because it does not work
in my version, but it is not the latest!

http://stackoverflow.com/questions/1103161/gdb-searching-for-source-directories/1327343#comment35550119_1327343

If yes, which one to use?