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.
See https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer for more information.
LeakSanitizer is enabled on the ASan bots on chromium.memory (both Linux and ChromeOS, with the exception of the "sandboxed" bot). All ASan trybots also have LSan enabled.
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 build/sanitizers/lsan_suppressions.cc. 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.
You can supply additional suppressions by adding
If you don't want to run LeakSanitizer locally, you can skip this section.
LeakSanitizer is supported on x86_64 Linux only. To build, follow the
ASan build instructions and add a
reference to is_lsan. Leak detection must not be enabled at build time, or LSan
will find leaks during the build process and fail. Make sure
not set when you build.
In GN, set up an "lsan" build directory (the directory naming is up to you):
gn args out/lsan
Add the args to the resulting editor:
is_asan = true
is_lsan = true
is_debug = false # Release build.
enable_nacl = false # Not necessary, but makes things faster.
And then build:
ninja -C out/lsan base_unittests
At run-time, add
detect_leaks=1 to ASAN_OPTIONS. You will also need to enable
symbolization, which is required for suppressions to work:
ASAN_OPTIONS="detect_leaks=1 symbolize=1 external_symbolizer_path=$SRC/third_party/llvm-build/Release+Asserts/bin/llvm-symbolizer" out/Release/base_unittests
A typical LSan report looks like this:
==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).
Note that LeakSanitizer is incompatible with the sandbox. You must pass
--no-sandbox if you want to run browser tests/Chrome with LSan.
(NOTE: the libstdc++ part is no longer required for Chromium, where we now use a custom libc++ binary for ASan builds.)
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
LD_LIBRARY_PATH="/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
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.
LSan can also be used without ASan instrumentation. In the build flags above,
omit the is_asan reference and specify only s_lsan. At runtime, use
LSAN_OPTIONS instead of
ASAN_OPTIONS. 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
LSAN_OPTIONS="detect_leaks=0" to prevent build errors (see