Leak Gauge

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: instrumentation in Gecko that produces a log file, and a script to post-process the log file.

Getting a log file

To get a log file, run the browser with these settings:

NSPR_LOG_MODULES=DOMLeak:5,DocumentLeak:5,nsDocShellLeak:5,NodeInfoManagerLeak:5
NSPR_LOG_FILE=nspr.log     # or any other filename of your choice

This overwrites any existing file named nspr.log. The browser runs with a negligible slowdown. For reliable results, exit the browser before post-processing the log file.

Post-processing the 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, the output looks like this:

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, the output looks like this:

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 find leaks, please file a bug report.