Restore the ability to check if LLVMCreateObjectFile was successful

[dotdash]

Summary

Until r216870 LLVMCreateObjectFile returned nullptr in case of an error,
so callers could check if the call was successful. Now, it always
returns an OwningBinary wrapped as an LLVMObjectFileRef, so callers
can't check if the call was successul.

This results in a segfault running e.g.

llvm-c-test --object-list-sections < /dev/null

So the old behaviour should be restored.

[• rafael]

OK as long as the commit includes a testcase.

[dotdash]

Added a test case.

[• rafael]

test/Bindings/llvm-c/objectfile.ll

2

We have a not utility that you can use instead of || true.

With no arguments "not foo" is true if "foo" is false, but not if foo crashes.

[dotdash]

Thanks, did not known about "not" before. Updated the test case to use it.

[• rafael]

LGTM, thanks a lot!

Closed by commit rL217279 (authored by bsteinbr).

lib/Object/Object.cpp

 }
 
 // ObjectFile creation
 LLVMObjectFileRef LLVMCreateObjectFile(LLVMMemoryBufferRef MemBuf) {
   std::unique_ptr<MemoryBuffer> Buf(unwrap(MemBuf));
   ErrorOr<std::unique_ptr<ObjectFile>> ObjOrErr(
       ObjectFile::createObjectFile(Buf->getMemBufferRef()));
   std::unique_ptr<ObjectFile> Obj;
-  if (ObjOrErr)
-    Obj = std::move(ObjOrErr.get());
-  auto *Ret = new OwningBinary<ObjectFile>(std::move(Obj), std::move(Buf));
+  if (!ObjOrErr)
+    return nullptr;
+
+  auto *Ret = new OwningBinary<ObjectFile>(std::move(ObjOrErr.get()), std::move(Buf));
   return wrap(Ret);
 }
 
 void LLVMDisposeObjectFile(LLVMObjectFileRef ObjectFile) {
   delete unwrap(ObjectFile);
 }
 
 // ObjectFile Section iterators

test/Bindings/llvm-c/objectfile.ll

+; RUN: not llvm-c-test --object-list-sections < /dev/null
+; This used to cause a segfault