How do I get line numbers in the debug output with clang's -fsanitize=address?

Question

I am trying to debug a memory error detected by clang with asan, but missed by valgrind. But I cannot get my clang built bina

Answer 1

For me, there is no llvm-symbolizer in /usr/bin, I need to first use

sudo ln -s /usr/bin/llvm-symbolizer-3.8 /usr/bin/llvm-symbolizer

to create the symbolizer and then add it to the PATH:

ASAN_SYMBOLIZER_PATH=/usr/bin/llvm-symbolizer ./test

Answer 2

Sometimes everything (path to the symboliser, environment variable etc) will be correct, but still you won't get file:line formatted output.

So run

dsymutil path/to/your.app/Contents/MacOS/binary

and then run the app and you'll get nicely formatted output. This is also mentioned in the docs.

Note that on macOS you may need to run dsymutil on your binary to have the file:line info in the AddressSanitizer reports.

http://clang.llvm.org/docs/AddressSanitizer.html#symbolizing-the-reports

Answer 3

Is addr2line what you are looking for?

 $ addr2line -e ./test 0x43e94f
 some/file.c:1234

Answer 4

Sometimes using a symbolizer with a version number will give the error:

ERROR: External symbolizer path is set to '/usr/bin/llvm-symbolizer-5.0' which isn't a known symbolizer. Please set the path to the llvm-symbolizer binary or other known tool.

This can be fixed by pointing to an unadorned llvm-symbolizer binary:

export ASAN_SYMBOLIZER_PATH=/usr/lib/llvm-5.0/bin/llvm-symbolizer

Then ran your executable as you normally would.

Answer 5

If we look at the clang AddressSanitizer documentation it says:

To make AddressSanitizer symbolize its output you need to set the ASAN_SYMBOLIZER_PATH environment variable to point to the llvm-symbolizer binary (or make sure llvm-symbolizer is in your $PATH):

and shows the the following example:

ASAN_SYMBOLIZER_PATH=/usr/local/bin/llvm-symbolizer ./a.out

As the OP noted, the install location may vary, but once you know where llvm-symbolizer is located the steps are the same.