Re: [PATCH] c++: spurious ADDR_EXPR after overload set pruning [PR107461]

[Jason Merrill <jason@redhat.com>]

On 2/2/23 13:09, Patrick Palka wrote:
> Here the ahead-of-time overload set pruning in finish_call_expr is
> unintentionally returning a CALL_EXPR whose pruned callee is wrapped in
> an ADDR_EXPR, despite the original callee not being wrapped in an
> ADDR_EXPR.  This ends up causing a bogus declaration matching error in
> the below testcase because the call to min in #1 is expressed as a
> CALL_EXPR to ADDR_EXPR to FUNCTION_DECL, whereas the level-lowered call
> to min in #2 is expressed instead as a CALL_EXPR to FUNCTION_DECL.
> 
> This patch fixes this by stripping this ADDR_EXPR appropriately.
> Thus the first call to min now gets expresssed as a CALL_EXPR to
> FUNCTION_DECL, matching the form it had before r12-6075-g2decd2cabe5a4f.
> 
> Bootstrapped and regtested on x86_64-pc-linu-xgnu, does this look OK
> for trunk and 12?

OK.  As a future direction, I'd think we want to do the same pruning for 
other forms of "FN".

Jason

> 	PR c++/107461
> 
> gcc/cp/ChangeLog:
> 
> 	* semantics.cc (finish_call_expr): Strip ADDR_EXPR from
> 	the selected callee during overload set pruning.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/template/friend75.C: New test.
> ---
>   gcc/cp/semantics.cc                      | 15 +++++++++-----
>   gcc/testsuite/g++.dg/template/friend75.C | 26 ++++++++++++++++++++++++
>   2 files changed, 36 insertions(+), 5 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/template/friend75.C
> 
> diff --git a/gcc/cp/semantics.cc b/gcc/cp/semantics.cc
> index b3afea85196..fe9262a257f 100644
> --- a/gcc/cp/semantics.cc
> +++ b/gcc/cp/semantics.cc
> @@ -2957,13 +2957,18 @@ finish_call_expr (tree fn, vec<tree, va_gc> **args, bool disallow_virtual,
>         if (TREE_CODE (result) == CALL_EXPR
>   	  && really_overloaded_fn (orig_fn))
>   	{
> -	  orig_fn = CALL_EXPR_FN (result);
> -	  if (TREE_CODE (orig_fn) == COMPONENT_REF)
> +	  tree sel_fn = CALL_EXPR_FN (result);
> +	  if (TREE_CODE (sel_fn) == COMPONENT_REF)
>   	    {
>   	      /* The non-dependent result of build_new_method_call.  */
> -	      orig_fn = TREE_OPERAND (orig_fn, 1);
> -	      gcc_assert (BASELINK_P (orig_fn));
> -	    }
> +	      sel_fn = TREE_OPERAND (sel_fn, 1);
> +	      gcc_assert (BASELINK_P (sel_fn));
> +	    }
> +	  else if (TREE_CODE (sel_fn) == ADDR_EXPR)
> +	    /* Undo the ADDR_EXPR callee wrapping performed by build_over_call
> +	       since the original callee didn't have it.  */
> +	    sel_fn = TREE_OPERAND (sel_fn, 0);
> +	  orig_fn = sel_fn;
>   	}
>   
>         result = build_call_vec (TREE_TYPE (result), orig_fn, orig_args);
> diff --git a/gcc/testsuite/g++.dg/template/friend75.C b/gcc/testsuite/g++.dg/template/friend75.C
> new file mode 100644
> index 00000000000..800d3043c8a
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/template/friend75.C
> @@ -0,0 +1,26 @@
> +// PR c++/107461
> +// { dg-do compile { target c++11 } }
> +
> +template<class T>
> +constexpr T min(T t0, T t1) {
> +  return t0 < t1 ? t0 : t1;
> +}
> +
> +template<int MAX>
> +struct Matrix;
> +
> +template<int MAXOP, int other_MAXOP>
> +Matrix<min(MAXOP, other_MAXOP)>
> +operator+(Matrix<MAXOP> const& lhs, Matrix<other_MAXOP> const& rhs); // #1
> +
> +template<int MAX>
> +struct Matrix {
> +  template<int MAXOP, int other_MAXOP>
> +  friend Matrix<min(MAXOP, other_MAXOP)>
> +  operator+(Matrix<MAXOP> const& lhs, Matrix<other_MAXOP> const& rhs); // #2
> +};
> +
> +void f() {
> +  Matrix<1> a;
> +  a+a;
> +}