What's the best way to tell CMake to use the LLVM linker llvm-link instead of GNU ld as linker? When configuring a project with
CXX=clang++ cmake <args> the default linker appears to be untouched, remaining usr/bin/ld (on Linux).
Is this possible without using a separate toolchain file?
This turns out to be unrelated to CMake: clang++ uses the system linker by default. For example,
echo "#include <atomic>\n int main() { return 0; }" \ | clang++ -x c++ -std=c++11 -stdlib=libc++ - uses /usr/bin/ld to link the application. To change the linker to llvm-link, one needs to first emit LLVM byte code, and then call the linker, e.g.:
echo "#include <atomic>\n int main() { return 0; }" \ | clang++ -x c++ -std=c++11 -stdlib=libc++ -S -emit-llvm -o - - \ | llvm-link -o binary - This bypasses /usr/bin/ld.
$PATH, or is it hardcoded into clang to use the one in /usr/bin/?
ld binary in other places besides your $PATH. I said "system linker" to refer to the standard linker of native object code as opposed to the LLVM byte code linker.As of 3.4, clang looks for the linker (ld) at GCCInstallation.getParentLibPath() + "/../" + GCCInstallation.getTriple().str() + "/bin" before it looks for ld on the path. You should be able to put your linker in /usr/lib/gcc/<arch><sub>-<vendor>-<sys>-<abi>/<version>/ld and have it called by clang in 1 step. To specify this location manually, use the undocumented -B flag. Unfortunately, I don't believe there is a way to alter the name of the linker that is searched for so using ld.gold or lld is going to require a symlink at the aforementioned location.
