[all-commits] [llvm/llvm-project] 4dc110: [ORC] Attempt to auto-claim responsibility for wea...

[lhames via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 4dc110a4b83c625502092b127ca0e9eb13824297
      https://github.com/llvm/llvm-project/commit/4dc110a4b83c625502092b127ca0e9eb13824297
  Author: Lang Hames <lhames at gmail.com>
  Date:   2021-01-27 (Wed, 27 Jan 2021)

  Changed paths:
    M llvm/lib/ExecutionEngine/Orc/ObjectLinkingLayer.cpp

  Log Message:
  -----------
  [ORC] Attempt to auto-claim responsibility for weak defs in ObjectLinkingLayer.

Compilers may insert new definitions during compilation, E.g. EH personality
function pointers, or named constant pool entries. This commit causes
ObjectLinkingLayer to attempt to claim responsibility for all weak definitions
in objects as they're linked. This is always safe (first claimant for each
symbol is granted responsibility, subsequent claims are rejected without error)
and prevents compiler-injected symbols from being dead-stripped (which they
will be if they remain unclaimed by anyone).

This change was motivated by errors seen by an out-of-tree client while testing
eh-frame support in JITLink ELF/x86-64: IR containing exceptions didn't define
DW.ref.__gxx_personality_v0 (since it's added by CodeGen), and this caused
DW.ref.__gxx_personality_v0 to be dead-stripped leading to linker failures.

No test case yet: We won't have a way to test in-tree until we enable JITLink
for lli on Linux.