[PATCH] Add a fallback mechanism for undefined atom.

[Rui Ueyama]

================
Comment at: lib/Core/Resolver.cpp:214
@@ +213,3 @@
+      // for COFF "weak external" symbol.
+      const UndefinedAtom *fallbackUndefAtom = undefAtom->fallback();
+      if (fallbackUndefAtom) {
----------------
kledzik at apple.com wrote:
> You need to re-test:
>   if (!_symbolTable.isDefined(undefName)
> because searchLibraries() may have already found a definition.
Fixed.


http://llvm-reviews.chandlerc.com/D1550