Max, I assigned it to you, but if you don't have time, feel free to give it back to me, I can also take a look at it.

hmm, my guess may not be true, I tried src/docs, and it works

One more strange behavior, not sure if it's related.

"time python tools/code_coverage/coverage.py url_unittests -c "out/coverage/url_unittests" -b out/coverage/ -o out/yuke -v"

real	0m11.583s
user	0m13.896s
sys	0m5.028s

Finishes within 20 seconds when filters are not specified, however,

"time python tools/code_coverage/coverage.py url_unittests -c "out/coverage/url_unittests" -b out/coverage/ -o out/yuke -f third_party/"

has been running over 5 minutes and still haven't finished.

Here is a full list of filters that will cause llvm to hang:

src/build
src/buildtool
src/third_party

For now, I'll blacklist them in the script until this is fixed at llvm side.

This issue seems pretty bad, I saw a few other cases where some filters cause llvm-cov to hang. I'll try to take a look this week, if I can't figure it out, I'll give it back to you next week when you're back :)

Interesting! This is the file causing the hang: https://github.com/llvm-mirror/libcxx/blob/master/test/std/experimental/filesystem/Inputs/static_test_env/bad_symlink

I haven't completely understood the details, but this for loop got stuck on this bad symbol link file:

https://cs.corp.google.com/piper///depot/google3/third_party/llvm/llvm/tools/llvm-cov/CodeCoverage.cpp?q=CodeCoverage.cpp&sq=package:piper+file://depot/google3+-file:google3/experimental&l=215

Forgot to mention, src/buildtools added libc++ as a third_party dependency, so this is why using src/buildtools as a filter hangs.

Landed https://reviews.llvm.org/rL329223 and https://reviews.llvm.org/rL329338