I am trying to play a bit with ASan on OS X and I found out that on recent OS X releases, compiler-rt tests fail to build and run with CMake. That's because OS X now provides relocatable SDKs with Xcode and has no system-wide standard headers/libs. I am aware that currently compiler-rt tests are supported only with CMake.
There are actually two issues:
- Newly built clang binary can't find the platform SDK. Either the SDKROOT env has to be set or -isysroot passed on command line.
- Newly build clang binary can't find c++ headers. It expects to find them in "../include/c++" relative to its binary. This issue goes away if you put libcxx into "llvm/projects/" and build libcxx simultaneously with llvm.
My proposed patch adds OS X detection into CMake to add the -isysroot parameter and it creates a symlink pointing from the build directory's include/c++ into Xcode's toolchain (but only if you don't simultaneously build libcxx). It also moves a similar SDKROOT detection from clang's lit config into a util function and uses it in compiler-rt lit tests as well.
One other solution to make the tests build and pass would be to enforce OS X users to set their SDKROOT env property (most OS X users don't have it set) and lit would need to be changed in a way to propagate this env property (it doesn't now). Installing a SDK into a system-wide location (e.g. /usr/include) is discouraged and deprecated on OS X, although manually installing Xcode Command Line Tools does that. Note that this will not solve the other issue (missing c++ headers).
The attached patch is three files, which should go into llvm, compiler-rt and clang projects respectively.