'llvm/IR/Constants.h' file not found

Question

I'm trying to make a compiler and I'm using llvm (C++ api) for intermediate and final code production. Though when trying to execute the command:

llvm.o: llvm.cpp llvm.h
    $(CPP) llvm.cpp -c -$(FLAGS) 

in my make file I'm getting the error:

In file included from llvm.cpp:6:
./opt.h:5:10: fatal error: 'llvm/IR/Constants.h' file not found
#include <llvm/IR/Constants.h>
         ^~~~~~~~~~~~~~~~~~~~~
1 error generated.

I'm using Mac Os (Sierra version 10.12.6) and I've installed llvm using brew (brew install llvm) so I can't understand how the library file can't be found.

Also my clang version:

bash-3.2$ clang --version
Apple LLVM version 9.0.0 (clang-900.0.37)
Target: x86_64-apple-darwin16.7.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin 

I've googled it a lot but couldn't find anything that solve my problem, any help appreciated !!!.

Answer 1

What're your FLAGS? You would need to provide linker flags and header search flags.

The following could help you:

llvm.o: llvm.cpp llvm.h
    $(CPP) llvm.cpp -c -$(FLAGS) `llvm-config --cxxflags --ldflags --libs`

Note that the --libs without any parameters will link your binary with all the LLVM libraries.

UPD:

On MacOS llvm-config and other tools are not added to the $PATH, because it would override system compiler and can screw your system in some way. You would need to use the full path, e.g. /usr/local/Cellar/llvm/3.9.0/bin/llvm-config. Make sure you use the right version here.

Also, make sure that your FLAGS are actually evaluated and not pasted to the command as is:

FLAGS=$(shell llvm-config --cxxflags --ldflags --libs)