Urgh I've just seen the Clang error with LTO builds on Travis

clang-3.9: error: unable to execute command: Segmentation fault (core dumped)
clang-3.9: error: linker command failed due to signal (use -v to see invocation)

@daniel-j-h weird, we are using clang 3.9.1 in node-osrm as well and we use it to compile osrm-backend. Any specifics about our setup?

Hm no, we are using the exact same Clang version in node-osrm:
https://github.com/Project-OSRM/node-osrm/blob/master/scripts/build.sh#L17

The failing build is Mason+Clang3.9.1+LTO specifically. I can try to reproduce locally.

/cc @springmeyer You might have some experience with clang 3.9 vs. LTO linking here? Anything that we do in node-osrm that we don't here?

Thanks for the ping. I recall that clang 3.9.0 and binutils 2.27 had a bad interaction that was fixed in clang 3.9.1: #3389 (comment). The fact that this is happening now with 3.9.1 is curious. I'll attempt to replicate later today and see if I see any clues.

I just spawned up a local Trusty Docker container, replicating the build environment with binutils, clang and really all deps. from Mason - except for zlib and libstdc++ (from ubuntu toolchain ppa, as we do on Travis).

But I can not replicate the segfault.

What I tried is clearing the Travis caches primarily for ccache and restarting the build.
But we still hit the Clang 3.9.1 segfault.

It works with Clang 4.0. Argh. At least we are unblocked by it now.

@springmeyer as soon as we merge this PR we depend on Clang 4.0 for all our production builds. Can you make sure to bundle a recent Clang 4.0 RC and once the release is out (should be a matter of days) bundle this.

Blocked by having LLVM 4 in Mason mapbox/mason#385

Blocked by having LLVM 4 in Mason mapbox/mason#385

llvm 4.0 packages are now available via mason. This includes separate packages:

• llvm (all tools in one download)
• clang++ - just the compiler + libraries needed for -fsanitize=* and -flto
• llvm-cov
• clang-tidy
• clang-format
• lldb
• include-what-you-use