[LLVM-C] Add Accessor for Mach-O Universal Binary Slices

[CodaFi]

Summary

Allow for retrieving an object file corresponding to an architecture-specific slice in a Mach-O universal binary file.

[whitequark]

LGTM

[CodaFi]

[NFC] Rebase

llvm/include/llvm-c/Object.h

 
 /**
  * Retrieve the specific type of a binary.
  *
  * @see llvm::object::Binary::getType
  */
 LLVMBinaryType LLVMBinaryGetType(LLVMBinaryRef BR);
 
+/*
+ * For a Mach-O universal binary file, retrieves the object file corresponding
+ * to the given architecture if it is present as a slice.
+ *
+ * If NULL is returned, the \p ErrorMessage parameter is populated with the
+ * error's description.  It is then the caller's responsibility to free this
+ * message by calling \c LLVMDisposeMessage.
+ *
+ * It is the responsiblity of the caller to free the returned object file by
+ * calling \c LLVMDisposeBinary.
+ */
+LLVMBinaryRef LLVMMachOUniversalBinaryCopyObjectForArch(LLVMBinaryRef BR,
+                                                        const char *Arch,
+                                                        size_t ArchLen,
+                                                        char **ErrorMessage);
 
 // ObjectFile creation
 LLVMObjectFileRef LLVMCreateObjectFile(LLVMMemoryBufferRef MemBuf);
 void LLVMDisposeObjectFile(LLVMObjectFileRef ObjectFile);
 
 // ObjectFile Section iterators
 LLVMSectionIteratorRef LLVMGetSections(LLVMObjectFileRef ObjectFile);
 void LLVMDisposeSectionIterator(LLVMSectionIteratorRef SI);

llvm/lib/Object/Object.cpp

 // library.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm-c/Object.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/Object/ObjectFile.h"
+#include "llvm/Object/MachOUniversal.h"
 
 using namespace llvm;
 using namespace object;
 
 inline OwningBinary<ObjectFile> *unwrap(LLVMObjectFileRef OF) {
   return reinterpret_cast<OwningBinary<ObjectFile> *>(OF);
 }
 
static LLVMBinaryType mapBinaryTypeToLLVMBinaryType(unsigned Kind) {
       default:
         llvm_unreachable("Unknown binary kind!");
       }
     }
   };
   return BinaryTypeMapper::mapBinaryTypeToLLVMBinaryType(unwrap(BR)->getType());
 }
 
+LLVMBinaryRef LLVMMachOUniversalBinaryCopyObjectForArch(LLVMBinaryRef BR,
+                                                        const char *Arch,
+                                                        size_t ArchLen,
+                                                        char **ErrorMessage) {
+  auto universal = cast<MachOUniversalBinary>(unwrap(BR));
+  Expected<std::unique_ptr<ObjectFile>> ObjOrErr(
+      universal->getObjectForArch({Arch, ArchLen}));
+  if (!ObjOrErr) {
+    *ErrorMessage = strdup(toString(ObjOrErr.takeError()).c_str());
+    return nullptr;
+  }
+  return wrap(ObjOrErr.get().release());
+}
+
 // ObjectFile creation
 LLVMObjectFileRef LLVMCreateObjectFile(LLVMMemoryBufferRef MemBuf) {
   std::unique_ptr<MemoryBuffer> Buf(unwrap(MemBuf));
   Expected<std::unique_ptr<ObjectFile>> ObjOrErr(
       ObjectFile::createObjectFile(Buf->getMemBufferRef()));
   std::unique_ptr<ObjectFile> Obj;
   if (!ObjOrErr) {
     // TODO: Actually report errors helpfully.