1129798 - mach command debugging improvements

Status: RESOLVED FIXED

(Firefox Build System :: Mach Core, enhancement)

Description

[Gregory Szorc [:gps]]

Patches forthcoming.

Comment 1

[Gregory Szorc [:gps]]

Attachment: Use pdb.runcall to debug mach commands

The previous debugger was setting a breakpoint in the mach dispatcher.
This required users to step into the main function to be called into.
Using pdb.runcall(), the debugger starts at the first line in the
executed command, which is far more useful.

Comment 2

[Gregory Szorc [:gps]]

I initially thought I'd have multiple patches here. I wanted to use pdb.post_mortem() to automatically enter a debugger from the raise point. However, combining pdb.post_mortem() with pdb.runcall() doesn't seem to work well. When the post mortem debugger is entered, it shows the frame as the first function in the dispatched mach command. I suspect that the debugger instance sets some state and pdb.post_mortem() isn't clearing it. Most weird.

Comment 3

[Gregory Szorc [:gps]]

So the traceback from sys.exc_info() doesn't have the correct frame info when pdb.runcall() is used. Digging through the source of pdb.py and bdb.py, I suspect extreme Python magic. I think a patch could be written, but it would involve calling a bunch of low-level pdb APIs. I'm not going to bother.

Comment 4

[Gregory Szorc [:gps]]

https://hg.mozilla.org/integration/fx-team/rev/71972672e292

Comment 5

[Ryan VanderMeulen [:RyanVM]]

https://hg.mozilla.org/mozilla-central/rev/71972672e292