Re: [PATCH 01/17] conf/bitbake.conf package.bbclass: fix dbg package not contain sources while -fdebug-prefix-map used

[Mark Hatle <mark.hatle@windriver.com>]

On 4/18/16 9:16 AM, Andreas Müller wrote:
> On Mon, Apr 18, 2016 at 3:55 PM, Burton, Ross <ross.burton@intel.com> wrote:
>>
>> On 18 April 2016 at 14:08, Hongxu Jia <hongxu.jia@windriver.com> wrote:
>>>
>>> If sysroot is required, override DEBUG_FLAGS to remove -fdebug-prefix-map
>>
>>
>> We should probably get this in the release notes, as many people do indeed
>> want remote debug to work.
>>
>> Can you tell gdb the base path to use when looking for symbols?  I've not
>> done remote GDB for some time but wouldn't "set substitute-path /
>> //my/sysroot/" work?  Or maybe /usr /my/sysroot/usr?
>>
>> If gdb can't be told then instead of having to replace all of DEBUG_FLAGS it
>> would be neat if the prefix mapping variables where in another variable that
>> could just be unset.
>>
>> Ross
> OK I think I could live with removing -fdebug-prefix-map for now.
> 
> A thought: We have the setting IMAGE_GEN_DEBUGFS - I have not yet
> tested. As far as I understand it creates an unstripped sysroot and
> does not affect target rootfs - is that correct? Does the sysroot
> created by IMAGE_GEN_DEBUGFS contain the sources? If yes we could set
> that as sysroot for gdb.
> 
> I think one of the problems we have here is that there is no reference
> way documented (or it is outdated) how remote debugging is meant to be
> performed.

Remote debugging is setup to always assume the remote side has access to a
debugable sysroot.  This isn't the project's sysroot, since that is transient,
but a REAL matching sysroot to the main image.

The easiest way to do this is to add the following to your local.conf:
   IMAGE_GEN_DEBUGFS = '1'

After this, look in your deploy directory and you will see the image to deploy
to the target, and also a matching 'debug' chunk that you keep on your local
host.  This way you -know- they are always in sync.

There is class material from the various Yocto Project Dev Day classes on using
this.


The alternative is tell GDB itself to map directories.  I don't remember offhand
the right option, but GDB supports remapping a directory reference to an actual
directory.  It should be pretty simple to re-map it -- but due to the transient
nature of the sysroot directory in the build, I don't recommend doing it this way.

--Mark