r? @jdm (or anyone else) Source-Repo: https://github.com/servo/servo Source-Revision: bfd4a0e5ffce6ceed6c4426279a8f3dcb3766fd1
1.9 KiB
Servo debugging guide
There are a few ways to debug Servo. mach
supports a --debug
flag that
searches a suitable debugger for you and runs servo with the appropriate
arguments under it:
./mach run --debug test.html
You can also specify an alternative debugger using the --debugger
flag:
./mach run --debugger=my-debugger test.html
You can also, of course, run directly your debugger on the Servo binary:
$ gdb --args ./target/debug/servo test.html
Debugging SpiderMonkey.
You can build Servo with a debug version of SpiderMonkey passing the
--debug-mozjs
flag to ./mach build
.
Note that this sometimes can cause problems when an existing build exists, so
you might have to delete the mozjs
build directory, or run ./mach clean
before your first --debug-mozjs
build.
Debugging Servo with rr.
To record a trace under rr you can either use:
$ ./mach run --debugger=rr testcase.html
Or:
$ rr record ./target/debug/servo testcase.html
Running WPT tests under rr's chaos mode.
Matt added a mode to Servo's testing commands to record traces of Servo running a test or set of tests until the result is unexpected.
To use this, you can pass the --chaos
argument to mach test-wpt
:
$ ./mach test-wpt --chaos path/to/test
Note that for this to work you need to have rr
in your PATH
.
Also, note that this might generate a lot of traces, so you might want to delete
them when you're done. They're under $HOME/.local/share/rr
.
Known gotchas
If you use a Haswell processor that supports Hardware Lock Ellision, rr might
not work for you. There's a rr
bug open about this. Until that gets
fixed, you can ensure that the parking_lot
dependency isn't built with the
nightly
feature, which as of this writing is the only dependency that uses it.