[cfe-dev] Fwd: Library calls for complex types and terminate scopes.

[Reid Kleckner via cfe-dev]

Maybe you could mark the runtime function nounwind when you get its
declaration here:
  llvm::Constant *Func = CGF.CGM.CreateBuiltinFunction(FTy, LibCallName
/*pass an AttributeSet here*/);

Then you won't have to call setDoesNotThrow() later.

On Tue, Nov 17, 2015 at 4:43 PM, Samuel F Antao via cfe-dev <
cfe-dev at lists.llvm.org> wrote:

> Hi all,
>
> I came across an issue that happens to trigger an assertion in clang if an
> operation with type type is implemented in a scope that happens to install
> a terminate scope in the exceptions stack. I see the issue while using
> complex arithmetic in OpenMP regions, but I believe that could also be a
> problem for non-openMP codes.
>
> The problem happens in `ComplexExprEmitter::EmitComplexBinOpLibCall` and
> is caused by an assertion in:
>
> ```
>   RValue Res = CGF.EmitCall(FuncInfo, Func, ReturnValueSlot(), Args,
>                             nullptr, &Call);
>   cast<llvm::CallInst>(Call)->setCallingConv(CGF.CGM.getBuiltinCC());
>   cast<llvm::CallInst>(Call)->setDoesNotThrow();
> ```
>
> `EHStack.requiresLandingPad()` is used by `EmitCall` and is true if we
> have a scope installed in the exceptions stack. This causes `EmitCall` to
> produce an invoke instruction instead of a call instruction.
>
> One of the ways to tackle the issue is use the proper attributes for the
> library function (e.g. no unwind). Is this the right thing to do? Or can
> these library calls throw in some cases?
>
> Any thoughts?
>
> Here is a simple code that replicates the problem:
> ```
> int main (int argc, char *argv[]){
>   double _Complex dc = (double)argc + 3*I;
>
>   dc *= dc;
>   #pragma omp parallel
>   {
>     dc *= dc;
>   }
>   printf("%lf %lf\n",creal(dc),cimag(dc));
>   return 0;
> }
> ```
>
> Thanks!
> Samuel
>
>
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