Re: [PATCH v9 08/10] Add tests for C/C++ musttail attributes

[Andi Kleen]

On Tue, Jul 16, 2024 at 02:51:13PM -0400, Jason Merrill wrote:
> On 7/16/24 12:18 PM, Andi Kleen wrote:
> > On Tue, Jul 16, 2024 at 11:17:14AM -0400, Jason Merrill wrote:
> > > On 7/16/24 11:15 AM, Andi Kleen wrote:
> > > > > In the adjusted test it looks like the types of f and g match, so I 
> > > > > wouldn't
> > > > > expect an error.
> > > > 
> > > > Good point! Missing the forest for the trees.
> > > > 
> > > > Anyways are the C++ patches ok with this change?
> > > 
> > > I'm still looking for a test which does error because the types are
> > > different.
> > 
> > Like this?
> 
> Where the called function returns C and the callee function does not.

In this case the attribute seems to get lost and it succeeds.

diff --git a/gcc/testsuite/g++.dg/musttail10.C 
b/gcc/testsuite/g++.dg/musttail10.C
index e454a6238a06..39f0ec38253d 100644
--- a/gcc/testsuite/g++.dg/musttail10.C
+++ b/gcc/testsuite/g++.dg/musttail10.C
@@ -28,12 +28,18 @@ class C
 public:
   C(double x) : x(x) {}
   ~C() { asm("":::"memory"); }
+  operator int() { return x; } 
 };
 
+template <class T>
+__attribute__((noinline, noclone, noipa))
+T g5() { [[gnu::musttail]] return f<C>(); } /* { dg-error "cannot tail-call" } 
*/
+
 int main()
 {
   g1<int>();
   g2<double>();
   g3<C>();
   g4<int>();
+  g5<int>();
 }