797308 - Preprocessing js files should use //@line

Status: RESOLVED INVALID

(Firefox Build System :: General, defect)

Description

[David Teller [:Yoric] - still alive but not very active]

We have a number of preprocessed JavaScript files on m-c. Unfortunately, for any of these files, any stack trace line number will be false. This is pretty annoying for debugging, especially for intermittent oranges.

Now, as it turns out, our JS VM supports directives

//@line 1234

specifically for this kind of issues.

We should adapt Preprocessor.py to introduce these directives.

Comment 1

[David Teller [:Yoric] - still alive but not very active]

I am willing to mentor this, btw.

Comment 2

[Mike Hommey [:glandium]]

It already does that.
http://mxr.mozilla.org/mozilla-central/source/config/Preprocessor.py#132

And for example, if I look in components/FeedWriter.js in an omni.ja from a try build i did recently, I can see:
//@line 652 "e:\builds\moz2_slave\try-w32\build\browser\components\feeds\src\FeedWriter.js"

Comment 3

[David Teller [:Yoric] - still alive but not very active]

In that case, the preprocessor is not applied uniformly.

Experiment:
- add the following line to test_jsctypes.js.in
   throw new Error("BOOM");
- launch the test.

I added this at line 1770 and the stack displayed the error at line 1755.

Comment 4

[David Teller [:Yoric] - still alive but not very active]

I confirm that the preprocessor does its job correctly on test_jsctypes.js.in. I will continue the investigation.

Comment 5

[David Teller [:Yoric] - still alive but not very active]

For the record, the investigation moved to:
- bug 246286;
- bug 797326.