[PATCH] Add a fallback mechanism for undefined atom.

[Shankar Kalpathi Easwaran]

  Its a very nice suggestion.  isAlias feature is I think the correct way of making the fallBack symbols working.

  Nick,

  The GNU linker for ELF searches the archive even if the current symbol is a weak symbol / common symbol.

  I think we might need two options in the resolver to check archives if weak/common.

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