c: Turn -Wincompatible-pointer-types into a permerror

The change to build_conditional_expr drops the downgrade
from a pedwarn to warning for builtins for C99 and later
language dialects.  It remains a warning in C89 mode (not
a permerror), as the -std=gnu89 -fno-permissive test shows.

gcc/

	* doc/invoke.texi (Warning Options): Document changes.

gcc/c/

	PR c/96284
	* c-typeck.cc (build_conditional_expr): Upgrade most pointer
	type mismatches to a permerror.
	(convert_for_assignment): Use permerror_opt and
	permerror_init for OPT_Wincompatible_pointer_types warnings.

gcc/testsuite/

	* gcc.dg/permerror-default.c (incompatible_pointer_types):
	Expect new permerror.
	* gcc.dg/permerror-gnu89-nopermissive.c
	(incompatible_pointer_types): Likewise.
	* gcc.dg/permerror-pedantic.c (incompatible_pointer_types):
	Likewise.
	* gcc.dg/permerror-system.c: Likewise.
	* gcc.dg/Wincompatible-pointer-types-2.c: Compile with
	-fpermissive due to expected errors.
	* gcc.dg/Wincompatible-pointer-types-5.c: New test.  Copied
	from gcc.dg/Wincompatible-pointer-types-2.c.  Expect errors.
	* gcc.dg/anon-struct-11.c: Compile with -fpermissive
	due to expected errors.
	* gcc.dg/anon-struct-11a.c: New test.  Copied from
	gcc.dg/anon-struct-11.c.  Expect errors.
	* gcc.dg/anon-struct-13.c: Compile with -fpermissive
	due to expected errors.
	* gcc.dg/anon-struct-13a.c: New test.  Copied from
	gcc.dg/anon-struct-13.c.  Expect errors.
	* gcc.dg/builtin-arith-overflow-4.c: Compile with -fpermissive
	due to expected errors.
	* gcc.dg/builtin-arith-overflow-4a.c: New test.  Copied from
	gcc.dg/builtin-arith-overflow-4.c.  Expect errors.
	* gcc.dg/c23-qual-4.c: Expect -Wincompatible-pointer-types errors.
	* gcc.dg/dfp/composite-type.c: Compile with -fpermissive
	due to expected errors.
	* gcc.dg/dfp/composite-type-2.c: New test.  Copied from
	gcc.dg/dfp/composite-type.c.  Expect errors.
	* gcc.dg/diag-aka-1.c: Compile with -fpermissive
	due to expected errors.
	* gcc.dg/diag-aka-1a.c: New test.  Copied from
	gcc.dg/diag-aka-1a.c.  Expect errors.
	* gcc.dg/enum-compat-1.c: Compile with -fpermissive
	due to expected errors.
	* gcc.dg/enum-compat-2.c: New test.  Copied from
	gcc.dg/enum-compat-1.c.  Expect errors.
	* gcc.dg/func-ptr-conv-1.c: Compile with -fpermissive
	due to expected errors.
	* gcc.dg/func-ptr-conv-2.c: New test.  Copied from
	gcc.dg/func-ptr-conv-1.c.  Expect errors.
	* gcc.dg/init-bad-7.c: Compile with -fpermissive
	due to expected errors.
	* gcc.dg/init-bad-7a.c: New test.  Copied from gcc.dg/init-bad-7.c.
	Expect errors.
	* gcc.dg/noncompile/incomplete-3.c (foo): Expect
	-Wincompatible-pointer-types error.
	* gcc.dg/param-type-mismatch-2.c (test8): Likewise.
	* gcc.dg/pointer-array-atomic.c: Compile with -fpermissive
	due to expected errors.
	* gcc.dg/pointer-array-atomic-2.c: New test.  Copied from
	gcc.dg/pointer-array-atomic.c.  Expect errors.
	* gcc.dg/pointer-array-quals-1.c (test): Expect
	-Wincompatible-pointer-types errors.
	* gcc.dg/transparent-union-1.c: Compile with -fpermissive
	due to expected errors.
	* gcc.dg/transparent-union-1a.c: New test.  Copied from
	gcc.dg/transparent-union-1.c.  Expect errors.
	* gcc.target/aarch64/acle/memtag_2a.c
	(test_memtag_warning_return_qualifier): Expect additional
	errors.
	* gcc.target/aarch64/sve/acle/general-c/load_2.c (f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/load_ext_gather_offset_1.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/load_ext_gather_offset_2.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/load_ext_gather_offset_3.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/load_ext_gather_offset_4.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/load_ext_gather_offset_5.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/load_ext_gather_offset_restricted_1.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/load_ext_gather_offset_restricted_2.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/load_ext_gather_offset_restricted_3.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/load_ext_gather_offset_restricted_4.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/sizeless-1.c (f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/sizeless-2.c (f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/store_1.c (f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/store_2.c (f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/store_scatter_index_1.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/store_scatter_index_restricted_1.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/store_scatter_offset_2.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general-c/store_scatter_offset_restricted_1.c
	(f1): Likewise.
	* gcc.target/aarch64/sve/acle/general/attributes_7.c
	(f1): Likewise.
	* gcc.target/i386/sse2-bfloat16-scalar-typecheck.c (footest):
	Expect -Wincompatible-pointer-types errors.
	* gcc.target/i386/vect-bfloat16-typecheck_1.c (footest): Likewise.
	* gcc.target/i386/vect-bfloat16-typecheck_2.c (footest): Likewise.

1 files changed, 35 insertions, 27 deletions

diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
index b03532a..a6edbc85 100644
--- a/gcc/c/c-typeck.cc
+++ b/gcc/c/c-typeck.cc
@@ -5463,8 +5463,15 @@ build_conditional_expr (location_t colon_loc, tree ifexp, bool ifexp_bcp,
       else
 	{
 	  int qual = ENCODE_QUAL_ADDR_SPACE (as_common);
-	  if (emit_diagnostic (bltin1 && bltin2 ? DK_WARNING : DK_PEDWARN,
-			       colon_loc, OPT_Wincompatible_pointer_types,
+	  diagnostic_t kind = DK_PERMERROR;
+	  if (!flag_isoc99)
+	    /* This downgrade to a warning ensures that -std=gnu89
+	       -pedantic-errors does not flag these mismatches between
+	       builtins as errors (as DK_PERMERROR would).  ISO C99
+	       and later do not have implicit function declarations,
+	       so the mismatch cannot occur naturally there.  */
+	    kind = bltin1 && bltin2 ? DK_WARNING : DK_PEDWARN;
+	  if (emit_diagnostic (kind, colon_loc, OPT_Wincompatible_pointer_types,
 			       "pointer type mismatch "
 			       "in conditional expression"))
 	    {
@@ -7602,46 +7609,47 @@ convert_for_assignment (location_t location, location_t expr_loc, tree type,
 		auto_diagnostic_group d;
 		range_label_for_type_mismatch rhs_label (rhstype, type);
 		gcc_rich_location richloc (expr_loc, &rhs_label);
-		if (pedwarn (&richloc, OPT_Wincompatible_pointer_types,
-			     "passing argument %d of %qE from incompatible "
-			     "pointer type", parmnum, rname))
+		if (permerror_opt (&richloc, OPT_Wincompatible_pointer_types,
+				   "passing argument %d of %qE from "
+				   "incompatible pointer type",
+				   parmnum, rname))
 		  inform_for_arg (fundecl, expr_loc, parmnum, type, rhstype);
 	      }
 	      break;
 	    case ic_assign:
 	      if (bltin)
-		pedwarn (location, OPT_Wincompatible_pointer_types,
-			 "assignment to %qT from pointer to "
-			 "%qD with incompatible type %qT",
-			 type, bltin, rhstype);
+		permerror_opt (location, OPT_Wincompatible_pointer_types,
+			       "assignment to %qT from pointer to "
+			       "%qD with incompatible type %qT",
+			       type, bltin, rhstype);
 	      else
-		pedwarn (location, OPT_Wincompatible_pointer_types,
-			 "assignment to %qT from incompatible pointer type %qT",
-			 type, rhstype);
+		permerror_opt (location, OPT_Wincompatible_pointer_types,
+			       "assignment to %qT from incompatible pointer "
+			       "type %qT", type, rhstype);
 	      break;
 	    case ic_init:
 	    case ic_init_const:
 	      if (bltin)
-		pedwarn_init (location, OPT_Wincompatible_pointer_types,
-			      "initialization of %qT from pointer to "
-			      "%qD with incompatible type %qT",
-			      type, bltin, rhstype);
+		permerror_init (location, OPT_Wincompatible_pointer_types,
+				"initialization of %qT from pointer to "
+				"%qD with incompatible type %qT",
+				type, bltin, rhstype);
 	      else
-		pedwarn_init (location, OPT_Wincompatible_pointer_types,
-			      "initialization of %qT from incompatible "
-			      "pointer type %qT",
-			      type, rhstype);
+		permerror_init (location, OPT_Wincompatible_pointer_types,
+				"initialization of %qT from incompatible "
+				"pointer type %qT",
+				type, rhstype);
 	      break;
 	    case ic_return:
 	      if (bltin)
-		pedwarn (location, OPT_Wincompatible_pointer_types,
-			 "returning pointer to %qD of type %qT from "
-			 "a function with incompatible type %qT",
-			 bltin, rhstype, type);
+		permerror_opt (location, OPT_Wincompatible_pointer_types,
+			       "returning pointer to %qD of type %qT from "
+			       "a function with incompatible type %qT",
+			       bltin, rhstype, type);
 	      else
-		pedwarn (location, OPT_Wincompatible_pointer_types,
-			 "returning %qT from a function with incompatible "
-			 "return type %qT", rhstype, type);
+		permerror_opt (location, OPT_Wincompatible_pointer_types,
+			       "returning %qT from a function with "
+			       "incompatible return type %qT", rhstype, type);
 	      break;
 	    default:
 	      gcc_unreachable ();