Debug Symbols: Difference between revisions

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Two types of packages can provide debug symbols:

==== Unstripped packages ====

To prevent stripping of a derivation, use the option <code>dontStrip = true;</code>. This still compiles with optimisation;

to compile with <code>-Og -ggdb</code> in addition to disabling stripping, you can use the function <code>enableDebugging</code>.

Let's take the example of <code>socat</code>.

If you install socat, then run

{{Commands|

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you see that you have debugging symbols for neither socat itself nor for dependent libraries.

Now, to build an unstripped socat:

Now, build an unstripped socat:

{{Commands|

$ nix-build -E 'with import <nixpkgs> {}; enableDebugging socat'

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==== NixOS ====

By toggling <code>environment.enableDebugInfo</code> to 'true' in <code>/etc/nixos/configuration.nix</code>, all

By toggling <code>environment.enableDebugInfo</code> to 'true' in <code>/etc/nixos/configuration.nix</code>, all separate debug info derivations in your <code>systemPackages</code> will have their debug output linked in <code>/run/current-system/sw/lib/debug/</code> and will be automatically available to gdb. Though note that this will not pick up debug symbols of dependencies – you will need to add the dependencies you want to debug to <code>environment.systemPackages</code> explicitly. If a derivation you are interested in does not have separate debug info enabled, you still have to override it with an overlay for example.

separate debug info derivations in your <code>systemPackages</code> will have their debug output linked in <code>/run/current-system/sw/lib/debug/</code> and

will be automatically available to gdb. If a derivation you are interested in does not have separate debug info enabled, you

==== dwarffs ====

still have to override it with an overlay for example.

To avoid the need to explicitly list every dependency in <code>environment.systemPackages</code> to have its debug output available, you can use [https://github.com/edolstra/dwarffs dwarffs]. It will create a virtual file system where gdb will be able to look for separate debug symbols for packages on-demand. The downside is that it might increase gdb start up time significantly.

==== nixseparatedebuginfo ====

[https://github.com/symphorien/nixseparatedebuginfod nixseparatedebuginfod] is a debuginfod server that can download the relevant debug outputs and source files as needed by debuginfod-capable tools. Compared to dwarffs, it does not require root access, and handles debug outputs of derivations not built by hydra (eg locally or on a custom binary cache) and source files. Gdb is built with support for debuginfod, and valgrind has support if you additionally install the bin output of elfutils.

[[Category:Nixpkgs]]

@@ Line 7: / Line 7: @@
 Two types of packages can provide debug symbols:
 ==== Unstripped packages ====
+To prevent stripping of a derivation, use the option <code>dontStrip = true;</code>. This still compiles with optimisation;
+to compile with <code>-Og -ggdb</code> in addition to disabling stripping, you can use the function <code>enableDebugging</code>.
 Let's take the example of <code>socat</code>.
 If you install socat, then run
 {{Commands|
@@ Line 30: / Line 31: @@
 you see that you have debugging symbols for neither socat itself nor for dependent libraries.
-Now, to build an unstripped socat:
+Now, build an unstripped socat:
 {{Commands|
 $ nix-build -E 'with import <nixpkgs> {}; enableDebugging socat'
@@ Line 125: / Line 126: @@
 ==== NixOS ====
-By toggling <code>environment.enableDebugInfo</code> to 'true' in <code>/etc/nixos/configuration.nix</code>, all
+By toggling <code>environment.enableDebugInfo</code> to 'true' in <code>/etc/nixos/configuration.nix</code>, all separate debug info derivations in your <code>systemPackages</code> will have their debug output linked in <code>/run/current-system/sw/lib/debug/</code> and will be automatically available to gdb. Though note that this will not pick up debug symbols of dependencies – you will need to add the dependencies you want to debug to <code>environment.systemPackages</code> explicitly. If a derivation you are interested in does not have separate debug info enabled, you still have to override it with an overlay for example.
-separate debug info derivations in your <code>systemPackages</code> will have their debug output linked in <code>/run/current-system/sw/lib/debug/</code> and
-will be automatically available to gdb. If a derivation you are interested in does not have separate debug info enabled, you
+==== dwarffs ====
-still have to override it with an overlay for example.
+To avoid the need to explicitly list every dependency in <code>environment.systemPackages</code> to have its debug output available, you can use [https://github.com/edolstra/dwarffs dwarffs]. It will create a virtual file system where gdb will be able to look for separate debug symbols for packages on-demand. The downside is that it might increase gdb start up time significantly.
+==== nixseparatedebuginfo ====
+[https://github.com/symphorien/nixseparatedebuginfod nixseparatedebuginfod] is a debuginfod server that can download the relevant debug outputs and source files as needed by debuginfod-capable tools. Compared to dwarffs, it does not require root access, and handles debug outputs of derivations not built by hydra (eg locally or on a custom binary cache) and source files. Gdb is built with support for debuginfod, and valgrind has support if you additionally install the bin output of elfutils.
+[[Category:Nixpkgs]]