Leak Gauge is a tool that can be used to detect certain kinds of leaks in Gecko, including those involving documents, window objects, and docshells. It has two parts: (a) instrumentation in Gecko that produces a log file, and (b) a script to post-process the log file.
Getting a log file
To get a log file, run the browser with the following environment variables set.
NSPR_LOG_MODULES=DOMLeak:5,DocumentLeak:5,nsDocShellLeak:5,NodeInfoManagerLeak:5 NSPR_LOG_FILE=nspr.log # or any other filename of your choice
This will overwrite any existing file called nspr.log. The browser will run with negligible slowdown. You must exit the browser before post-processing the log file or the results will be unreliable.
Post-processing a log file
Post-process the log file with tools/leak-gauge/leak-gauge.pl or tools/leak-gauge/leak-gauge.html.
If there are no leaks, output will look like the following.
Results of processing log leak.log : Summary: Leaked 0 out of 11 DOM Windows Leaked 0 out of 44 documents Leaked 0 out of 3 docshells Leaked content nodes in 0 out of 0 documents
If there are leaks, output will look like the following.
Results of processing log leak2.log : Leaked outer window 2c6e410 at address 2c6e410. Leaked outer window 2c6ead0 at address 2c6ead0. Leaked inner window 2c6ec80 (outer 2c6ead0) at address 2c6ec80. Summary: Leaked 13 out of 15 DOM Windows Leaked 35 out of 46 documents Leaked 4 out of 4 docshells Leaked content nodes in 42 out of 53 documents
If you see such a results, please file a bug.