[03/10] [COFF] Fix error handling in ResourceSectionRef

[mstorsjo]

Summary

Previously, the expression (Reader.readFoo()) was expanded twice, triggering asserts as one of the Error types ends up not checked (and as it was expanded twice, the method would end up called twice if it failed first).

Do we need a test with an intentionally broken object file to test this?

[rnk]

lgtm I don't think it needs a test.

llvm/trunk/lib/Object/COFFObjectFile.cpp

 }
 
 std::error_code BaseRelocRef::getRVA(uint32_t &Result) const {
   auto *Entry = reinterpret_cast<const coff_base_reloc_block_entry *>(Header + 1);
   Result = Header->PageRVA + Entry[Index].getOffset();
   return std::error_code();
 }
 
-#define RETURN_IF_ERROR(E)                                                     \
-  if (E)                                                                       \
-    return E;
+#define RETURN_IF_ERROR(Expr)                                                  \
+  do {                                                                         \
+    Error E = (Expr);                                                          \
+    if (E)                                                                     \
+      return std::move(E);                                                     \
+  } while (0)
 
 Expected<ArrayRef<UTF16>>
 ResourceSectionRef::getDirStringAtOffset(uint32_t Offset) {
   BinaryStreamReader Reader = BinaryStreamReader(BBS);
   Reader.setOffset(Offset);
   uint16_t Length;
   RETURN_IF_ERROR(Reader.readInteger(Length));
   ArrayRef<UTF16> RawDirString;