rustllvm: Add bindings to the LLVM linker

src/comp/lib/llvm.rs

@@ -848,7 +848,9 @@ fn LLVMRustWriteOutputFile(PassManagerRef PM, ModuleRef M,
         call. */
     fn LLVMRustGetLastError() -> sbuf;
 
-
+    /** Links LLVM modules together. `Src` is destroyed by this call and
+        must never be referenced again. */
+    fn LLVMLinkModules(ModuleRef Dest, ModuleRef Src) -> Bool;
 }
 
 native mod rustllvm = llvm_lib {

src/rustllvm/RustWrapper.cpp

@@ -12,6 +12,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/Linker.h"
 #include "llvm/PassManager.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/Support/FormattedStream.h"
@@ -25,12 +26,13 @@
 
 using namespace llvm;
 
-static char *LLVMRustError;
+static const char *LLVMRustError;
 
 extern "C" LLVMMemoryBufferRef
 LLVMRustCreateMemoryBufferWithContentsOfFile(const char *Path) {
   LLVMMemoryBufferRef MemBuf = NULL;
-  LLVMCreateMemoryBufferWithContentsOfFile(Path, &MemBuf, &LLVMRustError);
+  LLVMCreateMemoryBufferWithContentsOfFile(Path, &MemBuf,
+    const_cast<char **>(&LLVMRustError));
   return MemBuf;
 }
 
@@ -49,6 +51,20 @@ enum LLVMCodeGenFileType {
   LLVMNullFile         // Do not emit any output.
 };
 
+extern "C" bool LLVMLinkModules(LLVMModuleRef Dest, LLVMModuleRef Src) {
+  static std::string err;
+
+  // For some strange reason, unwrap() doesn't work here. "No matching
+  // function" error.
+  Module *DM = reinterpret_cast<Module *>(Dest);
+  Module *SM = reinterpret_cast<Module *>(Src);
+  if (Linker::LinkModules(DM, SM, &err)) {
+    LLVMRustError = err.c_str();
+    return false;
+  }
+  return true;
+}
+
 extern "C" void LLVMRustWriteOutputFile(LLVMPassManagerRef PMR,
                                         LLVMModuleRef M,
                                         const char *triple,

src/rustllvm/rustllvm.def.in

@@ -1,6 +1,7 @@
 LLVMRustCreateMemoryBufferWithContentsOfFile
 LLVMRustWriteOutputFile
 LLVMRustGetLastError
+LLVMLinkModules
 LLVMCreateObjectFile
 LLVMDisposeObjectFile
 LLVMGetSections