TipsAndTricks/DebugNativeRecipeWithGdb: Difference between revisions

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I recently had the need to debug a crash in a native binary that a layer I was working on invokes during the build.
I recently had the need to debug a crash in a native binary that a layer I was working on invokes during the build.


To debug the crash with gdb I had to do two things; 1) have the build system generate a binary with debug symbols and 2) teach gdb where to look for files.
To debug the crash with gdb I had to do two things; 1) have the build system generate a binary with debug symbols and 2) not have them stripped during installation to sysroot.


To debug a native binary with gdb you first need to ensure that the binaries in the sysroot don't have their debugging symbols stripped.
To enable debug symbols, usually one needs to add "-g" to the list of compiler flags. Unforunately how this is done is specific to each project - you need to inspect the
You can do this for all staged binaries by setting <code>INHIBIT_SYSROOT_STRIP = "1"</code> in your local.conf
source code tree and look for clues. For autoconf-based projects adding to CFLAGS environment variable is enough.
 
After the build has completed, inspect the compilation log to verify that -g is indeed there.
 
To ensure that the binaries in the sysroot don't have their debugging symbols stripped you need to set <code>INHIBIT_SYSROOT_STRIP = "1"</code> in your local.conf


Alternatively you might want to only inhibit stripping for specific recipes, this can be achieved using recipe OVERRIDES such as:
Alternatively you might want to only inhibit stripping for specific recipes, this can be achieved using recipe OVERRIDES such as:
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Note: you'll need to ensure any binaries you wish to debug are (re-)staged into the sysroot after changing this setting.
Note: you'll need to ensure any binaries you wish to debug are (re-)staged into the sysroot after changing this setting.
Once you have binaries with debugging symbols you can start a gdb session and teach it where to look for files.
I pointed gdb at our native sysroot with (from within a gsb session):
set sysroot /path/to/build/tmp/sysroots/x86_64-linux
As native binaries can also link to host libraries, especially libc, I also told gdb to look in both the sysroot and the host for shared libraries:
set solib-search-path /path/to/build/tmp/sysroots/x86_64-linux/usr/lib:/usr/lib64/:/lib
With those commands run I was ready to operate gbd as usual and quickly narrowed down the cause of the crash.


For more information on the gdb commands above see the gdb manual section [https://sourceware.org/gdb/current/onlinedocs/gdb/Files.html#Files "Commands to Specify Files"]
For more information on the gdb commands above see the gdb manual section [https://sourceware.org/gdb/current/onlinedocs/gdb/Files.html#Files "Commands to Specify Files"]
= To Do =
* Verify whether solib-search-path should include sysroot and host paths, or just *add* host paths.
* test it still works

Latest revision as of 14:16, 15 February 2017

How to debug native recipes with gdb

I recently had the need to debug a crash in a native binary that a layer I was working on invokes during the build.

To debug the crash with gdb I had to do two things; 1) have the build system generate a binary with debug symbols and 2) not have them stripped during installation to sysroot.

To enable debug symbols, usually one needs to add "-g" to the list of compiler flags. Unforunately how this is done is specific to each project - you need to inspect the source code tree and look for clues. For autoconf-based projects adding to CFLAGS environment variable is enough.

After the build has completed, inspect the compilation log to verify that -g is indeed there.

To ensure that the binaries in the sysroot don't have their debugging symbols stripped you need to set INHIBIT_SYSROOT_STRIP = "1" in your local.conf

Alternatively you might want to only inhibit stripping for specific recipes, this can be achieved using recipe OVERRIDES such as: 

INHIBIT_SYSROOT_STRIP_pn-swupd-server-native = "1"

I used the former as it allowed me to be certain of having all debugging symbols available.

Note: you'll need to ensure any binaries you wish to debug are (re-)staged into the sysroot after changing this setting.

For more information on the gdb commands above see the gdb manual section "Commands to Specify Files"

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