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  <ja...@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


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