LeakSanitizer (LSan) is a heap leak detector similar to HeapLeakChecker
or to the leak checker in Valgrind/Memcheck
. LSan can be run on top of AddressSanitizer
with no additional slowdown compared to plain ASan.
LeakSanitizer is enabled on the ASan bots on chromium.memory
(both Linux and ChromeOS). You can use the
trybot to verify that your CL is clean.
Ping earthdok@ if you encounter any issues.
My CL has benign (test-only, intentional etc) leaks, how do I suppress them?You should fix the CL instead. The leaks may be harmless, but letting them accumulate over time has a negative impact on the stability of our bots. If you leak memory intentionally, use an in-code annotation instead (see
Ideally, you should only land suppressions for leaks in third-party code that you have no control over. If that is the case, take a look at
tools/lsan/suppressions.txt. The syntax is as follows:
The wildcard will be matched against the function/module/source file name of each frame in the stack trace. Supported special characters are
^ (beginning of string) and
$ (end of string).
Please be careful not to make the wildcard too generic. The TSan v2
page has some examples of good and bad suppressions.
If you don't want to run LeakSanitizer locally, you can skip this section.
Building Chromium with ASan + LeakSanitizer
LeakSanitizer is supported on x86_64 Linux only. To build, follow the ASan
build instructions and add
GYP_DEFINES='asan=1 lsan=1' gclient runhooks
ninja -C out/Release base_unittests
Note: Leak detection must not be enabled at this time, or LSan will find leaks during the build process and fail. Make sure
ASAN_OPTIONS is not set when you build.
Using LeakSanitizer on top of ASan
At run-time, simply add
ASAN_OPTIONS="detect_leaks=1 symbolize=1" out/Release/base_unittests
You should see leak reports:
==18109==ERROR: LeakSanitizer: detected memory leaks
Direct leak of 1024 byte(s) in 1 object(s) allocated from:
#0 0x430205 in _Znam _asan_rtl_
#1 0xfc0edd in TestBody base/tools_sanity_unittest.cc:83
#2 0x10eeef7 in Run testing/gtest/src/gtest.cc:2067
#3 0x10f04e1 in Run testing/gtest/src/gtest.cc:2244
#4 0x10f1357 in Run testing/gtest/src/gtest.cc:2351
#5 0x10fe7b2 in RunAllTests testing/gtest/src/gtest.cc:4177
#6 0x10fdcbc in impl testing/gtest/src/gtest.cc:2051
#7 0x12b5d16 in Run base/test/test_suite.cc:167
#8 0x128eaf6 in main base/test/run_all_unittests.cc:8
#9 0x7f18a1dc576c in __libc_start_main /build/buildd/eglibc-2.15/csu/libc-start.c:226
#10 0x444a6c in _start ??:0
SUMMARY: LeakSanitizer: 1024 byte(s) leaked in 1 allocation(s).
You should also point LSan to the Chromium-specific suppressions file, which resides under
tools/lsan/suppressions.txt. Do as follows:
ASAN_OPTIONS="detect_leaks=1 symbolize=1" LSAN_OPTIONS="suppressions=tools/lsan/suppressions.txt" out/Release/base_unittests
Note that LeakSanitizer is incompatible with the sandbox. You must pass
--no-sandbox if you want to run browser_tests or the full Chromium with LSan.
Using debug versions of shared libraries
Be aware that ASan's fast stack unwinder depends on frame pointers, which are often missing in release versions of shared libraries. If you want to use the fast unwinder (enabled by default), you should at least install a debug version of libstdc++. This worked for us on Ubuntu:
sudo apt-get install libstdc++6-4.6-dbg
/usr/lib/x86_64-linux-gnu/debug" ASAN_OPTIONS="detect_leaks=1 strict_memcmp=0" out/Release/base_unittests
If you still see incomplete stack traces, you can disable the fast unwinder by adding
GLib may not play well with leak detection tools in the default mode. We recommend to pass
G_SLICE=always-malloc, especially if you're trying to reproduce a GLib-related leak.
Using LeakSanitizer without ASan
LSan can also be used without ASan instrumentation. In
GYP_GENERATORS above, omit
asan=1 and specify only
lsan=1. At runtime, use
LSAN_OPTIONS instead of
ASAN_OPTIONS, respectively. Disabling ASan instrumentation can bring a performance advantage, but be aware that this mode is not as well tested as the LSan+ASan mode.
In this mode leak detection is enabled by default. When building, you must explicitly set
LSAN_OPTIONS="detect_leaks=0" to prevent build errors (see above).