Re: [PATCH 2/2] c++: duplicate "use of deleted fn" diagnostic [PR106880]

[Jason Merrill <jason@redhat.com>]

On 3/23/23 17:18, Patrick Palka wrote:
> Here we're issuing a duplicate diagnostic for the use of the deleted
> foo, first from the CALL_EXPR case of tsubst_copy_and_build (which
> doesn't exit early upon failure), and again from from build_over_call
> when rebuilding the substituted CALL_EXPR.
> 
> We can fix this by exiting early upon failure of the first call, but
> this first call should always be redundant since build_over_call (or
> another subroutine of finish_call_expr) ought to reliably call mark_used
> for a suitable DECL_P callee anyway.
> 
> So this patch just gets rid of the first call to mark_used.
> 
> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> trunk?

OK.

> 	PR c++/106880
> 
> gcc/cp/ChangeLog:
> 
> 	* pt.cc (tsubst_copy_and_build) <case CALL_EXPR>: Don't call
> 	mark_used.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/cpp0x/deleted16.C: New test.
> ---
>   gcc/cp/pt.cc                           |  6 ------
>   gcc/testsuite/g++.dg/cpp0x/deleted16.C | 11 +++++++++++
>   2 files changed, 11 insertions(+), 6 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/cpp0x/deleted16.C
> 
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index 9b3cc33331c..060d2d38504 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -21176,12 +21176,6 @@ tsubst_copy_and_build (tree t,
>   	      }
>   	  }
>   
> -	/* Remember that there was a reference to this entity.  */
> -	if (function != NULL_TREE
> -	    && DECL_P (function)
> -	    && !mark_used (function, complain) && !(complain & tf_error))
> -	  RETURN (error_mark_node);
> -
>   	if (!maybe_fold_fn_template_args (function, complain))
>   	  return error_mark_node;
>   
> diff --git a/gcc/testsuite/g++.dg/cpp0x/deleted16.C b/gcc/testsuite/g++.dg/cpp0x/deleted16.C
> new file mode 100644
> index 00000000000..93cfb51eb3d
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/deleted16.C
> @@ -0,0 +1,11 @@
> +// PR c++/106880
> +// Verify we don't emit a "use of deleted function" diagnostic twice.
> +// { dg-do compile { target c++11 } }
> +
> +void foo() = delete;
> +
> +template<class T>
> +void f(T t) { foo(t); } // { dg-bogus "deleted function.*deleted function" }
> +                        // { dg-error "deleted function" "" { target *-*-*} .-1 }
> +
> +template void f(int);