Re: [PATCH] c++, v3: Fix up diagnostics about taking address of an immediate member function [PR102753]

[Jason Merrill <jason@redhat.com>]

On 11/25/21 09:38, Jakub Jelinek wrote:
> On Wed, Nov 24, 2021 at 09:07:48PM -0500, Jason Merrill wrote:
>>> --- gcc/cp/tree.c.jj	2021-11-24 15:05:23.371927735 +0100
>>> +++ gcc/cp/tree.c	2021-11-24 17:09:05.348164621 +0100
>>> @@ -5167,6 +5167,7 @@ make_ptrmem_cst (tree type, tree member)
>>>      tree ptrmem_cst = make_node (PTRMEM_CST);
>>>      TREE_TYPE (ptrmem_cst) = type;
>>>      PTRMEM_CST_MEMBER (ptrmem_cst) = member;
>>> +  PTRMEM_CST_LOCATION (ptrmem_cst) = input_location;
>>>      return ptrmem_cst;
>>>    }
>>
>> Please also change build_x_unary_op to improve PTRMEM_CST_LOCATION instead
>> of adding a wrapper, and teach cp_expr_location about PTRMEM_CST_LOCATION.
> 
> Done.  Though, had to also change convert_for_assignment from
> EXPR_LOC_OR_LOC to cp_expr_loc_or_input_loc and expand_ptrmemfunc_cst
> to copy over location to ADDR_EXPR from PTRMEM_CST.
> 
>>> --- gcc/cp/pt.c.jj	2021-11-24 15:05:23.336928234 +0100
>>> +++ gcc/cp/pt.c	2021-11-24 15:34:29.018014159 +0100
>>> @@ -17012,6 +17012,12 @@ tsubst_copy (tree t, tree args, tsubst_f
>>>    	r = build1 (code, type, op0);
>>
>> This should become build1_loc (EXPR_LOCATION (t), ...
> 
> Done.
>>
>>>    	if (code == ALIGNOF_EXPR)
>>>    	  ALIGNOF_EXPR_STD_P (r) = ALIGNOF_EXPR_STD_P (t);
>>> +	/* For addresses of immediate functions ensure we have EXPR_LOCATION
>>> +	   set for possible later diagnostics.  */
>>> +	if (code == ADDR_EXPR
>>> +	    && TREE_CODE (op0) == FUNCTION_DECL
>>> +	    && DECL_IMMEDIATE_FUNCTION_P (op0))
>>> +	  SET_EXPR_LOCATION (r, input_location);
>>
>> ...and then do this only if t didn't have a location.
> 
> And this too.
> 
> 2021-11-25  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR c++/102753
> 	* cp-tree.h (struct ptrmem_cst): Add locus member.
> 	(PTRMEM_CST_LOCATION): Define.
> 	* tree.c (make_ptrmem_cst): Set PTRMEM_CST_LOCATION to input_location.
> 	(cp_expr_location): Return PTRMEM_CST_LOCATION for PTRMEM_CST.
> 	* typeck.c (build_x_unary_op): Overwrite PTRMEM_CST_LOCATION for
> 	PTRMEM_CST instead of calling maybe_wrap_with_location.
> 	(cp_build_addr_expr_1): Don't diagnose taking address of
> 	immediate functions here.  Instead when taking their address make
> 	sure the returned ADDR_EXPR has EXPR_LOCATION set.
> 	(expand_ptrmemfunc_cst): Copy over PTRMEM_CST_LOCATION to
> 	ADDR_EXPR if taking address of immediate member function.
> 	(convert_for_assignment): Use cp_expr_loc_or_input_loc instead of
> 	EXPR_LOC_OR_LOC.
> 	* pt.c (tsubst_copy): Use build1_loc instead of build1.  Ensure
> 	ADDR_EXPR of immediate function has EXPR_LOCATION set.
> 	* cp-gimplify.c (cp_fold_r): Diagnose taking address of immediate
> 	functions here.  For consteval if don't walk THEN_CLAUSE.
> 	(cp_genericize_r): Move evaluation of calls to
> 	std::source_location::current from here to...
> 	(cp_fold): ... here.  Don't assert calls to immediate functions must
> 	be source_location_current_p, instead only constant evaluate
> 	calls to source_location_current_p.
> 
> 	* g++.dg/cpp2a/consteval20.C: Add some extra tests.
> 	* g++.dg/cpp2a/consteval23.C: Likewise.
> 	* g++.dg/cpp2a/consteval25.C: New test.
> 	* g++.dg/cpp2a/srcloc20.C: New test.
> 
> --- gcc/cp/cp-tree.h.jj	2021-11-25 08:35:39.856073838 +0100
> +++ gcc/cp/cp-tree.h	2021-11-25 14:25:33.411081733 +0100
> @@ -703,6 +703,7 @@ struct GTY(()) template_parm_index {
>   struct GTY(()) ptrmem_cst {
>     struct tree_common common;
>     tree member;
> +  location_t locus;
>   };
>   typedef struct ptrmem_cst * ptrmem_cst_t;
>   
> @@ -4726,6 +4727,11 @@ more_aggr_init_expr_args_p (const aggr_i
>   #define PTRMEM_CST_MEMBER(NODE) \
>     (((ptrmem_cst_t)PTRMEM_CST_CHECK (NODE))->member)
>   
> +/* For a pointer-to-member constant `X::Y' this is a location where
> +   the address of the member has been taken.  */
> +#define PTRMEM_CST_LOCATION(NODE) \
> +  (((ptrmem_cst_t)PTRMEM_CST_CHECK (NODE))->locus)
> +
>   /* The expression in question for a TYPEOF_TYPE.  */
>   #define TYPEOF_TYPE_EXPR(NODE) (TYPE_VALUES_RAW (TYPEOF_TYPE_CHECK (NODE)))
>   
> --- gcc/cp/tree.c.jj	2021-11-25 08:35:39.942072610 +0100
> +++ gcc/cp/tree.c	2021-11-25 14:31:32.784899701 +0100
> @@ -5196,6 +5196,7 @@ make_ptrmem_cst (tree type, tree member)
>     tree ptrmem_cst = make_node (PTRMEM_CST);
>     TREE_TYPE (ptrmem_cst) = type;
>     PTRMEM_CST_MEMBER (ptrmem_cst) = member;
> +  PTRMEM_CST_LOCATION (ptrmem_cst) = input_location;
>     return ptrmem_cst;
>   }
>   
> @@ -6040,6 +6041,8 @@ cp_expr_location (const_tree t_)
>         return STATIC_ASSERT_SOURCE_LOCATION (t);
>       case TRAIT_EXPR:
>         return TRAIT_EXPR_LOCATION (t);
> +    case PTRMEM_CST:
> +      return PTRMEM_CST_LOCATION (t);
>       default:
>         return EXPR_LOCATION (t);
>       }
> --- gcc/cp/typeck.c.jj	2021-11-25 08:32:50.585489416 +0100
> +++ gcc/cp/typeck.c	2021-11-25 15:22:25.554996949 +0100
> @@ -6497,7 +6497,7 @@ build_x_unary_op (location_t loc, enum t
>         exp = cp_build_addr_expr_strict (xarg, complain);
>   
>         if (TREE_CODE (exp) == PTRMEM_CST)
> -	exp = maybe_wrap_with_location (exp, loc);
> +	PTRMEM_CST_LOCATION (exp) = loc;
>         else
>   	protected_set_expr_location (exp, loc);
>       }
> @@ -6780,16 +6780,6 @@ cp_build_addr_expr_1 (tree arg, bool str
>   	    return error_mark_node;
>   	  }
>   
> -	if (TREE_CODE (t) == FUNCTION_DECL
> -	    && DECL_IMMEDIATE_FUNCTION_P (t)
> -	    && !in_immediate_context ())
> -	  {
> -	    if (complain & tf_error)
> -	      error_at (loc, "taking address of an immediate function %qD",
> -			t);
> -	    return error_mark_node;
> -	  }
> -
>   	type = build_ptrmem_type (context_for_name_lookup (t),
>   				  TREE_TYPE (t));
>   	t = make_ptrmem_cst (type, t);
> @@ -6816,15 +6806,6 @@ cp_build_addr_expr_1 (tree arg, bool str
>       {
>         tree stripped_arg = tree_strip_any_location_wrapper (arg);
>         if (TREE_CODE (stripped_arg) == FUNCTION_DECL
> -	  && DECL_IMMEDIATE_FUNCTION_P (stripped_arg)
> -	  && !in_immediate_context ())
> -	{
> -	  if (complain & tf_error)
> -	    error_at (loc, "taking address of an immediate function %qD",
> -		      stripped_arg);
> -	  return error_mark_node;
> -	}
> -      if (TREE_CODE (stripped_arg) == FUNCTION_DECL
>   	  && !mark_used (stripped_arg, complain) && !(complain & tf_error))
>   	return error_mark_node;
>         val = build_address (arg);
> @@ -6865,6 +6846,13 @@ cp_build_addr_expr_1 (tree arg, bool str
>   			      complain);
>       }
>   
> +  /* For addresses of immediate functions ensure we have EXPR_LOCATION
> +     set for possible later diagnostics.  */
> +  if (TREE_CODE (val) == ADDR_EXPR
> +      && TREE_CODE (TREE_OPERAND (val, 0)) == FUNCTION_DECL
> +      && DECL_IMMEDIATE_FUNCTION_P (TREE_OPERAND (val, 0)))
> +    SET_EXPR_LOCATION (val, input_location);
> +
>     return val;
>   }
>   
> @@ -9571,8 +9559,13 @@ expand_ptrmemfunc_cst (tree cst, tree *d
>   				 /*c_cast_p=*/0, tf_warning_or_error);
>   
>     if (!DECL_VIRTUAL_P (fn))
> -    *pfn = convert (TYPE_PTRMEMFUNC_FN_TYPE (type),
> -		    build_addr_func (fn, tf_warning_or_error));
> +    {
> +      tree t = build_addr_func (fn, tf_warning_or_error);
> +      if (TREE_CODE (t) == ADDR_EXPR
> +	  && DECL_IMMEDIATE_FUNCTION_P (fn))

Let's do this regardless of DECL_IMMEDIATE_FUNCTION_P.

OK with that change.

> +	SET_EXPR_LOCATION (t, PTRMEM_CST_LOCATION (cst));
> +      *pfn = convert (TYPE_PTRMEMFUNC_FN_TYPE (type), t);
> +    }
>     else
>       {
>         /* If we're dealing with a virtual function, we have to adjust 'this'
> @@ -9665,7 +9658,7 @@ convert_for_assignment (tree type, tree
>     tree rhstype;
>     enum tree_code coder;
>   
> -  location_t rhs_loc = EXPR_LOC_OR_LOC (rhs, input_location);
> +  location_t rhs_loc = cp_expr_loc_or_input_loc (rhs);
>     bool has_loc = EXPR_LOCATION (rhs) != UNKNOWN_LOCATION;
>     /* Strip NON_LVALUE_EXPRs since we aren't using as an lvalue,
>        but preserve location wrappers.  */
> --- gcc/cp/pt.c.jj	2021-11-25 08:39:32.000775006 +0100
> +++ gcc/cp/pt.c	2021-11-25 14:34:36.499250617 +0100
> @@ -17012,9 +17012,16 @@ tsubst_copy (tree t, tree args, tsubst_f
>         {
>   	tree type = tsubst (TREE_TYPE (t), args, complain, in_decl);
>   	tree op0 = tsubst_copy (TREE_OPERAND (t, 0), args, complain, in_decl);
> -	r = build1 (code, type, op0);
> +	r = build1_loc (EXPR_LOCATION (t), code, type, op0);
>   	if (code == ALIGNOF_EXPR)
>   	  ALIGNOF_EXPR_STD_P (r) = ALIGNOF_EXPR_STD_P (t);
> +	/* For addresses of immediate functions ensure we have EXPR_LOCATION
> +	   set for possible later diagnostics.  */
> +	if (code == ADDR_EXPR
> +	    && EXPR_LOCATION (r) == UNKNOWN_LOCATION
> +	    && TREE_CODE (op0) == FUNCTION_DECL
> +	    && DECL_IMMEDIATE_FUNCTION_P (op0))
> +	  SET_EXPR_LOCATION (r, input_location);
>   	return r;
>         }
>   
> --- gcc/cp/cp-gimplify.c.jj	2021-11-25 08:32:50.403492014 +0100
> +++ gcc/cp/cp-gimplify.c	2021-11-25 14:25:33.420081603 +0100
> @@ -900,8 +900,39 @@ struct cp_genericize_data
>   static tree
>   cp_fold_r (tree *stmt_p, int *walk_subtrees, void *data)
>   {
> -  tree stmt;
> -  enum tree_code code;
> +  tree stmt = *stmt_p;
> +  enum tree_code code = TREE_CODE (stmt);
> +
> +  switch (code)
> +    {
> +    case PTRMEM_CST:
> +      if (TREE_CODE (PTRMEM_CST_MEMBER (stmt)) == FUNCTION_DECL
> +	  && DECL_IMMEDIATE_FUNCTION_P (PTRMEM_CST_MEMBER (stmt)))
> +	{
> +	  if (!((hash_set<tree> *) data)->add (stmt))
> +	    error_at (PTRMEM_CST_LOCATION (stmt),
> +		      "taking address of an immediate function %qD",
> +		      PTRMEM_CST_MEMBER (stmt));
> +	  stmt = *stmt_p = build_zero_cst (TREE_TYPE (stmt));
> +	  break;
> +	}
> +      break;
> +
> +    case ADDR_EXPR:
> +      if (TREE_CODE (TREE_OPERAND (stmt, 0)) == FUNCTION_DECL
> +	  && DECL_IMMEDIATE_FUNCTION_P (TREE_OPERAND (stmt, 0)))
> +	{
> +	  error_at (EXPR_LOCATION (stmt),
> +		    "taking address of an immediate function %qD",
> +		    TREE_OPERAND (stmt, 0));
> +	  stmt = *stmt_p = build_zero_cst (TREE_TYPE (stmt));
> +	  break;
> +	}
> +      break;
> +
> +    default:
> +      break;
> +    }
>   
>     *stmt_p = stmt = cp_fold (*stmt_p);
>   
> @@ -917,12 +948,16 @@ cp_fold_r (tree *stmt_p, int *walk_subtr
>       }
>   
>     code = TREE_CODE (stmt);
> -  if (code == OMP_FOR || code == OMP_SIMD || code == OMP_DISTRIBUTE
> -      || code == OMP_LOOP || code == OMP_TASKLOOP || code == OACC_LOOP)
> +  switch (code)
>       {
>         tree x;
>         int i, n;
> -
> +    case OMP_FOR:
> +    case OMP_SIMD:
> +    case OMP_DISTRIBUTE:
> +    case OMP_LOOP:
> +    case OMP_TASKLOOP:
> +    case OACC_LOOP:
>         cp_walk_tree (&OMP_FOR_BODY (stmt), cp_fold_r, data, NULL);
>         cp_walk_tree (&OMP_FOR_CLAUSES (stmt), cp_fold_r, data, NULL);
>         cp_walk_tree (&OMP_FOR_INIT (stmt), cp_fold_r, data, NULL);
> @@ -961,6 +996,22 @@ cp_fold_r (tree *stmt_p, int *walk_subtr
>   	}
>         cp_walk_tree (&OMP_FOR_PRE_BODY (stmt), cp_fold_r, data, NULL);
>         *walk_subtrees = 0;
> +      return NULL;
> +
> +    case IF_STMT:
> +      if (IF_STMT_CONSTEVAL_P (stmt))
> +	{
> +	  /* Don't walk THEN_CLAUSE (stmt) for consteval if.  IF_COND is always
> +	     boolean_false_node.  */
> +	  cp_walk_tree (&ELSE_CLAUSE (stmt), cp_fold_r, data, NULL);
> +	  cp_walk_tree (&IF_SCOPE (stmt), cp_fold_r, data, NULL);
> +	  *walk_subtrees = 0;
> +	  return NULL;
> +	}
> +      break;
> +
> +    default:
> +      break;
>       }
>   
>     return NULL;
> @@ -1476,14 +1527,6 @@ cp_genericize_r (tree *stmt_p, int *walk
>   	  break;
>   	}
>   
> -      if (tree fndecl = cp_get_callee_fndecl_nofold (stmt))
> -	if (DECL_IMMEDIATE_FUNCTION_P (fndecl))
> -	  {
> -	    gcc_assert (source_location_current_p (fndecl));
> -	    *stmt_p = cxx_constant_value (stmt);
> -	    break;
> -	  }
> -
>         if (!wtd->no_sanitize_p
>   	  && sanitize_flags_p ((SANITIZE_NULL
>   				| SANITIZE_ALIGNMENT | SANITIZE_VPTR)))
> @@ -2629,6 +2672,14 @@ cp_fold (tree x)
>   	int sv = optimize, nw = sv;
>   	tree callee = get_callee_fndecl (x);
>   
> +        if (tree fndecl = cp_get_callee_fndecl_nofold (x))
> +	  if (DECL_IMMEDIATE_FUNCTION_P (fndecl)
> +	      && source_location_current_p (fndecl))
> +	    {
> +	      x = cxx_constant_value (x);
> +	      break;
> +	    }
> +
>   	/* Some built-in function calls will be evaluated at compile-time in
>   	   fold ().  Set optimize to 1 when folding __builtin_constant_p inside
>   	   a constexpr function so that fold_builtin_1 doesn't fold it to 0.  */
> --- gcc/testsuite/g++.dg/cpp2a/consteval20.C.jj	2021-11-25 08:32:50.713487589 +0100
> +++ gcc/testsuite/g++.dg/cpp2a/consteval20.C	2021-11-25 14:25:33.420081603 +0100
> @@ -10,10 +10,14 @@ constexpr S s;
>   int
>   bar ()
>   {
> +  auto c = &S::foo;			// { dg-error "taking address of an immediate function" }
> +  constexpr auto d = &S::foo;		// { dg-error "taking address of an immediate function" }
> +  static auto e = &S::foo;		// { dg-error "taking address of an immediate function" }
>     return (s.*&S::foo) ();		// { dg-error "taking address of an immediate function" }
>   }
>   
>   constexpr auto a = &S::foo;		// { dg-error "taking address of an immediate function" }
> +auto b = &S::foo;			// { dg-error "taking address of an immediate function" }
>   
>   consteval int
>   baz ()
> --- gcc/testsuite/g++.dg/cpp2a/consteval23.C.jj	2021-11-25 08:32:50.767486819 +0100
> +++ gcc/testsuite/g++.dg/cpp2a/consteval23.C	2021-11-25 14:25:33.420081603 +0100
> @@ -2,6 +2,7 @@
>   // { dg-do compile { target c++20 } }
>   
>   consteval int foo () { return 42; }
> +constexpr auto baz (int (*fn) ()) { return fn; }
>   
>   consteval int
>   bar (int (*fn) () = foo)
> @@ -11,3 +12,6 @@ bar (int (*fn) () = foo)
>   
>   static_assert (bar () == 42);
>   static_assert (bar (foo) == 42);
> +static_assert (bar (&foo) == 42);
> +static_assert (bar (baz (foo)) == 42);
> +static_assert (bar (baz (&foo)) == 42);
> --- gcc/testsuite/g++.dg/cpp2a/consteval25.C.jj	2021-11-25 14:25:33.420081603 +0100
> +++ gcc/testsuite/g++.dg/cpp2a/consteval25.C	2021-11-25 14:25:33.420081603 +0100
> @@ -0,0 +1,17 @@
> +// PR c++/102753
> +// { dg-do compile { target c++20 } }
> +// { dg-options "" }
> +
> +consteval int foo () { return 42; }
> +
> +consteval int
> +bar (int (*fn) ())
> +{
> +  return fn ();
> +}
> +
> +void
> +baz ()
> +{
> +  static_assert (bar (({ constexpr auto a = 1; foo; })) == 42);
> +}
> --- gcc/testsuite/g++.dg/cpp2a/srcloc20.C.jj	2021-11-25 14:25:33.420081603 +0100
> +++ gcc/testsuite/g++.dg/cpp2a/srcloc20.C	2021-11-25 14:25:33.420081603 +0100
> @@ -0,0 +1,44 @@
> +// { dg-do compile { target c++20 } }
> +
> +namespace std {
> +  struct source_location {
> +    struct __impl {
> +      const char *_M_file_name;
> +      const char *_M_function_name;
> +      unsigned int _M_line, _M_column;
> +    };
> +    const __impl *__ptr;
> +    constexpr source_location () : __ptr (nullptr) {}
> +    static consteval source_location
> +    current (const void *__p = __builtin_source_location ()) {
> +      source_location __ret;
> +      __ret.__ptr = static_cast <const __impl *> (__p);
> +      return __ret;
> +    }
> +    constexpr const char *file_name () const {
> +      return __ptr ? __ptr->_M_file_name : "";
> +    }
> +    constexpr const char *function_name () const {
> +      return __ptr ? __ptr->_M_function_name : "";
> +    }
> +    constexpr unsigned line () const {
> +      return __ptr ? __ptr->_M_line : 0;
> +    }
> +    constexpr unsigned column () const {
> +      return __ptr ? __ptr->_M_column : 0;
> +    }
> +  };
> +}
> +
> +using namespace std;
> +
> +auto a = source_location::current;		// { dg-error "taking address of an immediate function" }
> +constexpr auto b = &source_location::current;	// { dg-error "taking address of an immediate function" }
> +
> +void
> +foo ()
> +{
> +  auto c = &source_location::current;		// { dg-error "taking address of an immediate function" }
> +  constexpr auto d = source_location::current;	// { dg-error "taking address of an immediate function" }
> +  static auto e = source_location::current;	// { dg-error "taking address of an immediate function" }
> +}
> 
> 
> 	Jakub
>