Dual-Abi Linking
If you get one of these:
undefined reference to `_ZNK4llvm17SubtargetFeatures9getStringB5cxx11Ev'
undefined reference to `llvm::SubtargetFeatures::getString() const'
This is because of C++'s Dual ABI. Most likely LLVM was compiled with one compiler while Zig was compiled with a different one, for example GCC vs clang.
LLVM, Clang, and Zig must all be compiled with the same C++ compiler.
Undefined references in liblldELF.a
Building with LLVM 17 has zlib as a new requirement.
If your system has static zlib then -DZIG_STATIC_ZLIB=ON needs to be specified to use it (e.g. cmake .. -DZIG_STATIC_ZLIB=ON).
Arch Linux, Gentoo, Fedora 32+
The Clang packages in these distributions do not contain static libraries, which Zig tries to use by default.
Instead, one should link against the shared lib libclang-cpp.so.
For building stage1, set ZIG_SHARED_LLVM:
cmake .. -DZIG_SHARED_LLVM=ON
For building stage2, pass -Dstatic-llvm=false to Zig.
Fedora also doesn't ship by default with the static libraries for lib stdc++.
This will result in link errors for symbols like std::string.
You can fix this by installing the following package: dnf install libstdc++-static.
Ubuntu/Debian
The LLVM repositories/packages are listed at https://apt.llvm.org/. The following packages that are not listed must be installed: liblld-17-dev, libclang-17-dev (as well as at least libllvm17 from the listed packages).
macOS
On macOS, you must force static linking of LLVM using -DZIG_STATIC_LLVM=on. The full invocation will then look like:
cmake .. -DCMAKE_PREFIX_PATH="$(brew --prefix llvm@17);$(brew --prefix zstd)" -DZIG_STATIC_LLVM=on
After upgrading LLVM, it's often necessary to remove the CMake cache and build directories:
rm CMakeCache.txt
rm -rf CMakeFiles
Then try running the cmake command again.