I want to write a C++ function that takes an llvm::Module
, which is already linked, and output it to an executable file. It should use the llvm/clang API rather than forking a process and invoking the command-line clang.
After looking through the llvm/clang source code, the closest thing I've found is to output a Module
to a .o file. For example, the llc tool (tools/llc/llc.cpp) accomplishes this by calling TargetMachine::addPassesToEmitFile(...)
.
An alternative would be to write the Module
to a .bc file, then create a CompilerInstance
and call ExecuteCompilerInvocation
(as in tools/clang/tools/driver/cc1_main.cpp). But then there's the overhead of file I/O.
So, am I asking for something possible, or must I fall back on the alternative?
Edit: (Of course this is possible. It happens somewhere in the clang source code, I just can't find it.)
Not possible! clang
does not create the executable itself. It invokes ld
.
Found it in tools/clang/lib/Driver/Tools.cpp. In the ConstructJob
functions for the various platforms (darwin::Link::ConstructJob
, solaris::Link::ConstructJob
, etc.), it does this:
const char *Exec =
Args.MakeArgString(getToolChain().GetProgramPath("ld"));
C.addCommand(new Command(JA, *this, Exec, CmdArgs));
(For visualstudio::Link::ConstructJob
, it instead invokes link.exe
.)
Edit: In retrospect, it would have been faster to find this out by tracing clang
's system calls with dtruss
(Mac) or strace
(Linux).
Edit: I ended up using the Clang driver API for building and linking. I wrote up some example code.