[LLVMdev] Why clang++ doesn't set 'noreturn' flag on declarations of __cxa_throw and _Unwind_Resume_or_Rethrow ?

John McCall rjmccall at apple.com
Thu Jul 15 17:51:49 PDT 2010

On Jul 15, 2010, at 3:31 PM, Yuri wrote:
> When I compile some code with the near-trunk clang++ I get this:

Please send clang-specific questions to cfe-dev at cs.uiuc.edu.

> ...
>   tail call void @_Unwind_Resume_or_Rethrow(i8* %exn2) noreturn
>   unreachable
> ...
> declare void @_Unwind_Resume_or_Rethrow(i8*)
> ...
> Same with __cxa_throw. 'noreturn' is missing on declarations.
> This seems to be a bug.

It really shouldn't make a difference;  the call site should take priority anyway.

> Also can _Unwind_Resume_or_Rethrow actually return? When I run some 
> simple exception code in JIT I see that this function actually returns 
> and then SEGVs.

I have no idea what system you're on, but _Unwind_Resume_or_Rethrow really
isn't allowed to return.


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