[LLVMdev] [lld] ELF needs type for SharedLibraryAtom.

[Michael Spencer]

The following code currently links incorrectly when linking against a
dynamic libc on Ubuntu 12.10 unless -fpic is specified.

#include <stdio.h>

int main() {
  fputs("hi\n", stdout);
}

The reason is that stdout gets a R_X86_64_PC32 relocation, but is of type
Object. The ELF writer can't see this, and assumes all R_X86_64_PC32
relocations in dynamic outputs are to functions and thus need PLT entries.
The correct behavior is to treat this as a R_X86_64_GOTPCREL relocation. As
this is what both gnu-ld and gold do.

To handle this correctly we will need to add type information to
SharedLibraryAtom. We will also need to know about STT_COMMON in the future.

- Michael Spencer
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