Re: [PATCH] c++, v2: Fix up calls to static operator() or operator[] [PR107624]

[Jason Merrill <jason@redhat.com>]

On 11/16/22 03:25, Jakub Jelinek wrote:
> On Tue, Nov 15, 2022 at 04:49:27PM -0500, Jason Merrill wrote:
>>> Or do you want to outline the
>>> 	  if (result != error_mark_node
>>> 	      && TREE_CODE (TREE_TYPE (cand->fn)) != METHOD_TYPE
>>> 	      && TREE_SIDE_EFFECTS (obj))
>>> 	    {
>>> 	      /* But avoid the implicit lvalue-rvalue conversion when 'a'
>>> 		 is volatile.  */
>>> 	      tree a = obj;
>>> 	      if (TREE_THIS_VOLATILE (a))
>>> 		a = build_this (a);
>>> 	      if (TREE_SIDE_EFFECTS (a))
>>> 		result = build2 (COMPOUND_EXPR, TREE_TYPE (result), a, result);
>>> 	    }
>>> part that is now repeated 4 times to some helper function?  If yes,
>>> any suggestion on a good name?
>>
>> Please.  Maybe keep_unused_object_arg?
> 
> So like this?
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

OK.

> 2022-11-16  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR c++/107624
> 	* call.cc (keep_unused_object_arg): New function.
> 	(build_op_call): Use it.
> 	(build_op_subscript): Likewise.
> 	(build_new_op): Similarly for ARRAY_REF.
> 	(build_new_method_call): Likewise.
> 	* decl.cc (grok_op_properties): For C++20 and earlier, if operator[]
> 	is static member function, require exactly one parameter rather than
> 	exactly two parameters.
> 
> 	* g++.dg/cpp23/static-operator-call4.C: New test.
> 	* g++.dg/cpp23/subscript10.C: New test.
> 	* g++.dg/cpp23/subscript11.C: New test.
> 
> --- gcc/cp/call.cc.jj	2022-11-15 07:59:57.337231337 +0100
> +++ gcc/cp/call.cc	2022-11-15 23:10:14.077666314 +0100
> @@ -5017,6 +5017,33 @@ build_operator_new_call (tree fnname, ve
>      return ret;
>   }
>   
> +/* Evaluate side-effects from OBJ before evaluating call
> +   to FN in RESULT expression.
> +   This is for expressions of the form `obj->fn(...)'
> +   where `fn' turns out to be a static member function and
> +   `obj' needs to be evaluated.  `fn' could be also static operator[]
> +   or static operator(), in which cases the source expression
> +   would be `obj[...]' or `obj(...)'.  */
> +
> +static tree
> +keep_unused_object_arg (tree result, tree obj, tree fn)
> +{
> +  if (result == NULL_TREE
> +      || result == error_mark_node
> +      || TREE_CODE (TREE_TYPE (fn)) == METHOD_TYPE
> +      || !TREE_SIDE_EFFECTS (obj))
> +    return result;
> +
> +  /* But avoid the implicit lvalue-rvalue conversion when `obj' is
> +     volatile.  */
> +  tree a = obj;
> +  if (TREE_THIS_VOLATILE (a))
> +    a = build_this (a);
> +  if (TREE_SIDE_EFFECTS (a))
> +    return build2 (COMPOUND_EXPR, TREE_TYPE (result), a, result);
> +  return result;
> +}
> +
>   /* Build a new call to operator().  This may change ARGS.  */
>   
>   tree
> @@ -5137,7 +5164,13 @@ build_op_call (tree obj, vec<tree, va_gc
>         else if (TREE_CODE (cand->fn) == FUNCTION_DECL
>   	       && DECL_OVERLOADED_OPERATOR_P (cand->fn)
>   	       && DECL_OVERLOADED_OPERATOR_IS (cand->fn, CALL_EXPR))
> -	result = build_over_call (cand, LOOKUP_NORMAL, complain);
> +	{
> +	  result = build_over_call (cand, LOOKUP_NORMAL, complain);
> +	  /* In an expression of the form `a()' where cand->fn
> +	     which is operator() turns out to be a static member function,
> +	     `a' is none-the-less evaluated.  */
> +	  result = keep_unused_object_arg (result, obj, cand->fn);
> +	}
>         else
>   	{
>   	  if (TREE_CODE (cand->fn) == FUNCTION_DECL)
> @@ -7046,6 +7079,12 @@ build_new_op (const op_location_t &loc,
>   		  gcc_unreachable ();
>   		}
>   	    }
> +
> +	  /* In an expression of the form `a[]' where cand->fn
> +	     which is operator[] turns out to be a static member function,
> +	     `a' is none-the-less evaluated.  */
> +	  if (code == ARRAY_REF)
> +	    result = keep_unused_object_arg (result, arg1, cand->fn);
>   	}
>         else
>   	{
> @@ -7302,6 +7341,11 @@ build_op_subscript (const op_location_t
>   	      /* Specify evaluation order as per P0145R2.  */
>   	      CALL_EXPR_ORDERED_ARGS (call) = op_is_ordered (ARRAY_REF) == 1;
>   	    }
> +
> +	  /* In an expression of the form `a[]' where cand->fn
> +	     which is operator[] turns out to be a static member function,
> +	     `a' is none-the-less evaluated.  */
> +	  result = keep_unused_object_arg (result, obj, cand->fn);
>   	}
>         else
>   	gcc_unreachable ();
> @@ -11494,21 +11538,11 @@ build_new_method_call (tree instance, tr
>   	      /* In an expression of the form `a->f()' where `f' turns
>   		 out to be a static member function, `a' is
>   		 none-the-less evaluated.  */
> -	      if (TREE_CODE (TREE_TYPE (fn)) != METHOD_TYPE
> -		  && !is_dummy_object (instance)
> -		  && TREE_SIDE_EFFECTS (instance))
> -		{
> -		  /* But avoid the implicit lvalue-rvalue conversion when 'a'
> -		     is volatile.  */
> -		  tree a = instance;
> -		  if (TREE_THIS_VOLATILE (a))
> -		    a = build_this (a);
> -		  if (TREE_SIDE_EFFECTS (a))
> -		    call = build2 (COMPOUND_EXPR, TREE_TYPE (call), a, call);
> -		}
> -	      else if (call != error_mark_node
> -		       && DECL_DESTRUCTOR_P (cand->fn)
> -		       && !VOID_TYPE_P (TREE_TYPE (call)))
> +	      if (!is_dummy_object (instance))
> +		call = keep_unused_object_arg (call, instance, fn);
> +	      if (call != error_mark_node
> +		  && DECL_DESTRUCTOR_P (cand->fn)
> +		  && !VOID_TYPE_P (TREE_TYPE (call)))
>   		/* An explicit call of the form "x->~X()" has type
>   		   "void".  However, on platforms where destructors
>   		   return "this" (i.e., those where
> --- gcc/cp/decl.cc.jj	2022-11-15 07:59:57.321231551 +0100
> +++ gcc/cp/decl.cc	2022-11-15 13:13:51.814356965 +0100
> @@ -15400,6 +15400,10 @@ grok_op_properties (tree decl, bool comp
>   	    pedwarn (loc, OPT_Wc__23_extensions, "%qD may be a static member "
>   		     "function only with %<-std=c++23%> or %<-std=gnu++23%>",
>   		     decl);
> +	  if (operator_code == ARRAY_REF)
> +	    /* static operator[] should have exactly one argument
> +	       for C++20 and earlier, so that it isn't multidimensional.  */
> +	    op_flags = OVL_OP_FLAG_UNARY;
>   	}
>         else if (DECL_STATIC_FUNCTION_P (decl))
>   	{
> --- gcc/testsuite/g++.dg/cpp23/static-operator-call4.C.jj	2022-11-15 11:26:28.187511136 +0100
> +++ gcc/testsuite/g++.dg/cpp23/static-operator-call4.C	2022-11-15 11:27:19.684814244 +0100
> @@ -0,0 +1,37 @@
> +// PR c++/107624
> +// { dg-do run { target c++11 } }
> +// { dg-options "" }
> +
> +int n[3];
> +struct S {
> +  static void operator() (int x) { n[0] |= (1 << x); }	// { dg-warning "may be a static member function only with" "" { target c++20_down } }
> +  static void baz (int x) { n[1] |= (1 << x); }
> +  int s;
> +};
> +volatile S s[2];
> +
> +S &
> +foo (int x)
> +{
> +  static S t;
> +  n[2] |= (1 << x);
> +  return t;
> +}
> +
> +int
> +main ()
> +{
> +  int i = 0;
> +  foo (0) (0);
> +  if (n[0] != 1 || n[1] || n[2] != 1)
> +    __builtin_abort ();
> +  foo (1).baz (1);
> +  if (n[0] != 1 || n[1] != 2 || n[2] != 3)
> +    __builtin_abort ();
> +  s[i++] (2);
> +  if (i != 1 || n[0] != 5 || n[1] != 2 || n[2] != 3)
> +    __builtin_abort ();
> +  s[--i].baz (3);
> +  if (i != 0 || n[0] != 5 || n[1] != 10 || n[2] != 3)
> +    __builtin_abort ();
> +}
> --- gcc/testsuite/g++.dg/cpp23/subscript10.C.jj	2022-11-15 11:27:48.810420112 +0100
> +++ gcc/testsuite/g++.dg/cpp23/subscript10.C	2022-11-15 13:07:02.974885454 +0100
> @@ -0,0 +1,46 @@
> +// PR c++/107624
> +// { dg-do run { target c++11 } }
> +// { dg-options "" }
> +
> +int n[3];
> +struct S {
> +  static int &operator[] (int x) { n[0] |= (1 << x); return n[2]; }	// { dg-warning "may be a static member function only with" "" { target c++20_down } }
> +#if __cpp_multidimensional_subscript >= 202211L
> +  static int &operator[] () { n[0] |= (1 << 8); return n[2]; }
> +  static int &operator[] (int y, int z, int w) { n[0] |= (1 << y) | (1 << z) | (1 << w); return n[2]; }
> +#endif
> +  int s;
> +};
> +volatile S s[2];
> +
> +S &
> +foo (int x)
> +{
> +  static S t;
> +  n[1] |= (1 << x);
> +  return t;
> +}
> +
> +int
> +main ()
> +{
> +  int i = 0;
> +  foo (0) [0]++;
> +  if (n[0] != 1 || n[1] != 1 || n[2] != 1)
> +    __builtin_abort ();
> +  s[i++][2]++;
> +  if (i != 1 || n[0] != 5 || n[1] != 1 || n[2] != 2)
> +    __builtin_abort ();
> +#if __cpp_multidimensional_subscript >= 202211L
> +  foo (3) []++;
> +  if (n[0] != 261 || n[1] != 9 || n[2] != 3)
> +    __builtin_abort ();
> +  int y = 10;
> +  int z = 10;
> +  int w = 13;
> +  foo (4) [y++, ++z, w++]++;
> +  if (n[0] != 11525 || n[1] != 25 || n[2] != 4
> +      || y != 11 || z != 11 || w != 14)
> +    __builtin_abort ();
> +#endif
> +}
> --- gcc/testsuite/g++.dg/cpp23/subscript11.C.jj	2022-11-15 13:14:50.938557460 +0100
> +++ gcc/testsuite/g++.dg/cpp23/subscript11.C	2022-11-15 13:19:20.681910074 +0100
> @@ -0,0 +1,11 @@
> +// { dg-do compile { target c++11 } }
> +// { dg-options "" }
> +
> +struct S {
> +  static int &operator[] (int);	// { dg-warning "may be a static member function only with" "" { target c++20_down } }
> +  static int &operator[] ();	// { dg-warning "may be a static member function only with" "" { target c++20_down } }
> +				// { dg-error "'static int& S::operator\\\[\\\]\\\(\\\)' must have exactly one argument" "" { target c++20_down } .-1 }
> +  static int &operator[] (int, int, int);	// { dg-warning "may be a static member function only with" "" { target c++20_down } }
> +				// { dg-error "'static int& S::operator\\\[\\\]\\\(int, int, int\\\)' must have exactly one argument" "" { target c++20_down } .-1 }
> +  int s;
> +};
> 
> 
> 	Jakub
>