To catch the nastier kind of bugs, you can run your code with Address Sanitizer and Undefined Behavior Sanitizer. This is mostly done automagically by various CI systems for each PR, but you may want to do it locally as well. The process slightly varies depending on the compiler you want to use and which part of the test suite you want to run.
To build with sanitizers in mkosi, create a file 20-local.conf in mkosi.default.d/ and add the following contents:
The value of
SANITIZERS is passed directly to meson’s
b_sanitize option, See
https://mesonbuild.com/Builtin-options.html#base-options for the format expected by the option. Currently,
only the sanitizers supported by gcc can be used, which are
Note that this will only work with a recent version of mkosi (>= 14 or by running mkosi directly from source).
gcc compiles in sanitizer libraries dynamically by default, so you need to get
the shared libraries first - on Fedora these are shipped as a separate packages
libasan for Address Sanitizer and
libubsan for Undefined Behavior Sanitizer).
The compilation itself is then a matter of simply adding
meson. That’s it - following executions of
meson test and integrations tests
test/ subdirectory will run with sanitizers enabled. However, to get
truly useful results, you should tweak the runtime configuration of respective
sanitizers; e.g. in systemd we set the following environment variables:
In case of clang things are somewhat different - the sanitizer libraries are compiled in statically by default. This is not an issue if you plan to run only the unit tests, but for integration tests you’ll need to convince clang to use the dynamic versions of sanitizer libraries.
First of all, pass
-shared-libsan to both
CXXFLAGS are necessary for
is then the same as in case of gcc, simply add
meson call and use the same environment variables for runtime configuration.
After this, you’ll probably notice that all compiled binaries complain about
libclang_rt.asan* library. To fix this, you have to install clang’s
runtime libraries, usually shipped in the
compiler-rt package. As these libraries
are installed in a non-standard location (non-standard for
need to manually direct binaries to the respective runtime libraries.
# Optionally locate the respective runtime DSO $ ldd build/systemd | grep libclang_rt.asan libclang_rt.asan-x86_64.so => not found libclang_rt.asan-x86_64.so => not found $ find /usr/lib* /usr/local/lib* -type f -name libclang_rt.asan-x86_64.so 2>/dev/null /usr/lib64/clang/7.0.1/lib/libclang_rt.asan-x86_64.so # Set the LD_LIBRARY_PATH accordingly export LD_LIBRARY_PATH=/usr/lib64/clang/7.0.1/lib/ # If the path is correct, the "not found" message should change to an actual path $ ldd build/systemd | grep libclang_rt.asan libclang_rt.asan-x86_64.so => /usr/lib64/clang/7.0.1/lib/libclang_rt.asan-x86_64.so (0x00007fa9752fc000)
This should help binaries to correctly find necessary sanitizer DSOs.
Also, to make the reports useful,
llvm-symbolizer tool is required (usually
part of the
The reason why you need to force dynamic linking in case of
clang is that some
applications make use of
libsystemd, which is compiled with sanitizers as well.
However, if a standard (uninstrumented) application loads an instrumented library,
it will immediately fail due to unresolved symbols. To fix/workaround this, you
need to pre-load the ASan DSO using
LD_PRELOAD=/path/to/asan/dso, which will
make things work as expected in most cases. This will, obviously, not work with
statically linked sanitizer libraries.
These shenanigans are performed automatically when running the integration test
test/TEST-??-*) and are located in
but not only, in the