[llvm-bugs] [Bug 27498] clang emits memcpy for std::swap, which can introduce undefined behavior

via llvm-bugs llvm-bugs at lists.llvm.org
Sun Apr 24 08:25:10 PDT 2016


whitequark <whitequark at whitequark.org> changed:

           What    |Removed                     |Added
             Status|RESOLVED                    |REOPENED
         Resolution|DUPLICATE                   |---

--- Comment #2 from whitequark <whitequark at whitequark.org> ---
Sorry but I am reopening this. Specifically because the generated IR violates
LLVM's own invariats! To quote LangRef for @llvm.memcpy: "The ‘llvm.memcpy.*‘
intrinsics copy a block of memory from the source location to the destination
location, which are not allowed to overlap."

It might be that the fix is adjusting the contract of @llvm.memcpy--it is not
my call. But I would say that the current self-contradictory behavior is

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