[PATCH] D56624: [Sanitizers] UBSan unreachable incompatible with ASan in the presence of `noreturn` calls

[Evgenii Stepanov via Phabricator via cfe-commits]

eugenis added a comment.

> Because "expect_noreturn" calls are allowed to return, the compiler must behave as they could. In particular, this means that unpoisoning the stack before expect_noreturn calls (given the current semantics) is premature.

I don't think that's true. A hypothetical function

  maybe_longjmp(jmp_buf env)

that checks an opaque condition needs stack unpoisoning before the call, in the absense of a better solution.

One possible optimization that I can think of is splitting code after the call into a separate basic block and marking it as cold.
Admittedly, that's unlikely to have big impact in practice. I'd guess that [[expect_noreturn]] calls are typically not very hot in the first place.


Repository:
  rL LLVM

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https://reviews.llvm.org/D56624