[all-commits] [llvm/llvm-project] f4dd1b: [AMDGPU] Fix leak and self-assignment in copy assi...

[Fraser Cormack via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: f4dd1bc8fc625d3938f95b9d06aaaeebd2e90dca
      https://github.com/llvm/llvm-project/commit/f4dd1bc8fc625d3938f95b9d06aaaeebd2e90dca
  Author: Fraser Cormack <fraser at codeplay.com>
  Date:   2024-09-11 (Wed, 11 Sep 2024)

  Changed paths:
    M llvm/lib/Target/AMDGPU/SIMachineFunctionInfo.h

  Log Message:
  -----------
  [AMDGPU] Fix leak and self-assignment in copy assignment operator (#107847)

A static analyzer identified that this operator was unsafe in the case
of self-assignment.

In the placement new statement, StringValue's copy constructor was being
implicitly called, which received a reference to "itself". In fact, it
was being passed an old StringValue at the same address - one whose
lifetime had already ended. The copy constructor was thus copying fields
from a dead object.

We need to be careful when switching active union members, and calling
the destructor on the old StringValue will avoid memory leaks which I
believe the old code exhibited.



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