Add a way to print a backtrace without stopping/crashing Godot

[qarmin]

Describe the project you are working on

Godot Engine

Describe the problem or limitation you are having in your project

For now Godot print some error messages when starts godotengine/godot#49623 so checking each error with gdb or Qt Creator is slow.

Describe the feature / enhancement and how it helps to overcome the problem or limitation

Function like print_backtrace() could print exactly same backtrace as in crash e.g.

[1] /usr/bin/godots() [0x174c080] (/mnt/Miecz/godot3.2/platform/x11/crash_handler_x11.cpp:54)
[2] /lib/x86_64-linux-gnu/libc.so.6(+0x41040) [0x7fece20b9040] (??:0)
[3] Object::get(StringName const&, bool*) const (/mnt/Miecz/godot3.2/core/object.cpp:488)
[4] Viewport::_notification(int) (/mnt/Miecz/godot3.2/scene/main/viewport.cpp:401 (discriminator 2))
[5] Viewport::_notificationv(int, bool) (/mnt/Miecz/godot3.2/scene/main/viewport.h:89 (discriminator 14))
[6] Object::notification(int, bool) (/mnt/Miecz/godot3.2/core/object.cpp:929)
[7] SceneTree::_notify_group_pause(StringName const&, int) (/mnt/Miecz/godot3.2/scene/main/scene_tree.cpp:969)
[8] SceneTree::iteration(float) (/mnt/Miecz/godot3.2/scene/main/scene_tree.cpp:478 (discriminator 2))
[9] Main::iteration() (/mnt/Miecz/godot3.2/main/main.cpp:2075)
[10] OS_X11::run() (/mnt/Miecz/godot3.2/platform/x11/os_x11.cpp:3626)
[11] /usr/bin/godots(main+0x326) [0x1742d0c] (/mnt/Miecz/godot3.2/platform/x11/godot_x11.cpp:57)
[12] /lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xd5) [0x7fece20a0565] (??:0)
[13] /usr/bin/godots(_start+0x2e) [0x174292e] (??:?)

but without crashing entire app, to help find functions which executed current one.

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

Not sure but maybe extracting code from crash handler should be enough(this needs to be done for each platform)
https://github.com/godotengine/godot/blob/8f7f5846397297fff6e8a08f89bc60ce658699cc/platform/linuxbsd/crash_handler_linuxbsd.cpp#L48-L121

https://www.gnu.org/software/libc/manual/html_node/Backtraces.html

If this enhancement will not be used often, can it be worked around with a few lines of script?

Cannot print C++ backtrace from GDScript(but with this feature this could be possible but probably useless)

Is there a reason why this should be core and not an add-on in the asset library?

This cannot be added as addon

[Calinou]

You can use CRASH_NOW() to do this in C++, but it can't be done from scripting (or without crashing the engine).
Edit (December 2021): OS.crash() is now exposed to scripting by godotengine/godot#55603.

[timothyqiu]

For now Godot print some error messages when starts godotengine/godot#49623 so checking each error with gdb or Qt Creator is slow.

I think you can try conditional breakpoints.

[qarmin]

Simple patch which works only for Linux(I have no idea if this code should be inside OS class or somewhere else) patch.txt

[Calinou]

godotengine/godot#91006 implements the ability to print GDScript backtraces at any time, but it won't print the C++ side of the backtrace.