[PATCH] sectiongroup support

[Shankar Kalpathi Easwaran]

  I dont think the multithreaded model of processing all the object files first is going to work with the ELF linker, as resolution happens in the way input files are processed from command line.

  This is what I see with the GNU linker :-

  a) The groups are being resolved as and when input files are processed by the resolver. We cannot delay processing the group members after the resolver has processed all files.
  b) Consider the below example :-

  ELF foo.o contains

  section 1: SHT_GROUP , name=“g1”, content=3
  section 3:
        symbol: name=“global-f1”, size=30
        symbol: name=“global-f2”, size=16


  ELF bar.o contains:

  section 1: SHT_GROUP , name=“g1”, content=3
  section 3:
        symbol: name=“global-f1”, size=30
        symbol: name=“global-f2”, size=16
        symbol: name=“global-f3”, size=16

  ELF libarchive.a contains
        symbol: name=“global-f3”, size=30


  With the command line ld foo.o bar.o libarchive.a, when symbols from bar.o are processed, **global-f3 becomes a undefined symbol** and pulls the global-f3 from libarchive.a

  How do we handle all these cases with lld ?

http://llvm-reviews.chandlerc.com/D2961