PR c/83656 - missing -Wbuiltin-declaration-mismatch on declaration without prototype

gcc/c/ChangeLog:

	PR c/83656
	* c-decl.c (header_for_builtin_fn): Declare.
	(diagnose_mismatched_decls): Diagnose declarations of built-in
	functions without a prototype.
	* c-typeck.c (maybe_warn_builtin_no_proto_arg): New function.
	(convert_argument): Same.
	(convert_arguments): Factor code out into convert_argument.
	Detect mismatches between built-in formal arguments in calls
	to built-in without prototype.
	(build_conditional_expr): Same.
	(type_or_builtin_type): New function.
	(convert_for_assignment): Add argument.  Conditionally issue
	warnings instead of errors for mismatches.

gcc/testsuite/ChangeLog:

	PR c/83656
	* gcc.dg/20021006-1.c
	* gcc.dg/Wbuiltin-declaration-mismatch.c: New test.
	* gcc.dg/Wbuiltin-declaration-mismatch-2.c: New test.
	* gcc.dg/Wbuiltin-declaration-mismatch-3.c: New test.
	* gcc.dg/Wbuiltin-declaration-mismatch-4.c: New test.
	* gcc.dg/Walloca-16.c: Adjust.
	* gcc.dg/Wrestrict-4.c: Adjust.
	* gcc.dg/Wrestrict-5.c: Adjust.
	* gcc.dg/atomic/stdatomic-generic.c: Adjust.
	* gcc.dg/atomic/stdatomic-lockfree.c: Adjust.
	* gcc.dg/initpri1.c: Adjust.
	* gcc.dg/pr15698-1.c: Adjust.
	* gcc.dg/pr69156.c: Adjust.
	* gcc.dg/pr83463.c: Adjust.
	* gcc.dg/redecl-4.c: Adjust.
	* gcc.dg/tls/thr-init-2.c: Adjust.
	* gcc.dg/torture/pr55890-2.c: Adjust.
	* gcc.dg/torture/pr55890-3.c: Adjust.
	* gcc.dg/torture/pr67741.c: Adjust.
	* gcc.dg/torture/stackalign/sibcall-1.c: Adjust.
	* gcc.dg/torture/tls/thr-init-1.c: Adjust.
	* gcc.dg/tree-ssa/builtins-folding-gimple-ub.c: Adjust.

From-SVN: r266194

gcc/c/ChangeLog

+2018-11-15  Martin Sebor  <msebor@redhat.com>
+
+	PR c/83656
+	* c-decl.c (header_for_builtin_fn): Declare.
+	(diagnose_mismatched_decls): Diagnose declarations of built-in
+	functions without a prototype.
+	* c-typeck.c (maybe_warn_builtin_no_proto_arg): New function.
+	(convert_argument): Same.
+	(convert_arguments): Factor code out into convert_argument.
+	Detect mismatches between built-in formal arguments in calls
+	to built-in without prototype.
+	(build_conditional_expr): Same.
+	(type_or_builtin_type): New function.
+	(convert_for_assignment): Add argument.  Conditionally issue
+	warnings instead of errors for mismatches.
+
 2018-11-13  David Malcolm  <dmalcolm@redhat.com>
 
 	* c-decl.c: Replace "source_location" with "location_t".

gcc/c/c-decl.c

@@ -604,6 +604,7 @@ static tree grokparms (struct c_arg_info *, bool);
 static void layout_array_type (tree);
 static void warn_defaults_to (location_t, int, const char *, ...)
     ATTRIBUTE_GCC_DIAG(3,4);
+static const char *header_for_builtin_fn (enum built_in_function);
 
 /* T is a statement.  Add it to the statement-tree.  This is the
    C/ObjC version--C++ has a slightly different version of this
@@ -1887,12 +1888,25 @@ diagnose_mismatched_decls (tree newdecl, tree olddecl,
 	    *oldtypep = oldtype = trytype;
 	  else
 	    {
+	      const char *header
+		= header_for_builtin_fn (DECL_FUNCTION_CODE (olddecl));
+	      location_t loc = DECL_SOURCE_LOCATION (newdecl);
+	      if (warning_at (loc, OPT_Wbuiltin_declaration_mismatch,
+			      "conflicting types for built-in function %q+D; "
+			      "expected %qT",
+			      newdecl, oldtype)
+		  && header)
+		{
+		  /* Suggest the right header to include as the preferred
+		     solution rather than the spelling of the declaration.  */
+		  rich_location richloc (line_table, loc);
+		  maybe_add_include_fixit (&richloc, header, true);
+		  inform (&richloc,
+			  "%qD is declared in header %qs", olddecl, header);
+		}
 	      /* If types don't match for a built-in, throw away the
 		 built-in.  No point in calling locate_old_decl here, it
 		 won't print anything.  */
-	      warning (OPT_Wbuiltin_declaration_mismatch,
-		       "conflicting types for built-in function %q+D",
-		       newdecl);
 	      return false;
 	    }
 	}
@@ -2026,15 +2040,33 @@ diagnose_mismatched_decls (tree newdecl, tree olddecl,
 	 can't validate the argument list) the built-in definition is
 	 overridden, but optionally warn this was a bad choice of name.  */
       if (fndecl_built_in_p (olddecl)
-	  && !C_DECL_DECLARED_BUILTIN (olddecl)
-	  && (!TREE_PUBLIC (newdecl)
-	      || (DECL_INITIAL (newdecl)
-		  && !prototype_p (TREE_TYPE (newdecl)))))
+	  && !C_DECL_DECLARED_BUILTIN (olddecl))
 	{
-	  warning (OPT_Wshadow, "declaration of %q+D shadows "
-		   "a built-in function", newdecl);
-	  /* Discard the old built-in function.  */
-	  return false;
+	  if (!TREE_PUBLIC (newdecl)
+	      || (DECL_INITIAL (newdecl)
+		  && !prototype_p (TREE_TYPE (newdecl))))
+	    {
+	      warning_at (DECL_SOURCE_LOCATION (newdecl),
+			  OPT_Wshadow, "declaration of %qD shadows "
+			  "a built-in function", newdecl);
+	      /* Discard the old built-in function.  */
+	      return false;
+	    }
+
+	  if (!prototype_p (TREE_TYPE (newdecl)))
+	    {
+	      /* Set for built-ins that take no arguments.  */
+	      bool func_void_args = false;
+	      if (tree at = TYPE_ARG_TYPES (oldtype))
+		func_void_args = VOID_TYPE_P (TREE_VALUE (at));
+
+	      if (extra_warnings && !func_void_args)
+		warning_at (DECL_SOURCE_LOCATION (newdecl),
+			    OPT_Wbuiltin_declaration_mismatch,
+			    "declaration of built-in function %qD without "
+			    "a prototype; expected %qT",
+			    newdecl, TREE_TYPE (olddecl));
+	    }
 	}
 
       if (DECL_INITIAL (newdecl))

gcc/doc/invoke.texi

@@ -7063,9 +7063,26 @@ attributes.
 @item -Wno-builtin-declaration-mismatch
 @opindex Wno-builtin-declaration-mismatch
 @opindex Wbuiltin-declaration-mismatch
-Warn if a built-in function is declared with the wrong signature or 
-as non-function.
-This warning is enabled by default.
+Warn if a built-in function is declared with an incompatible signature
+or as a non-function, or when a built-in function declared with a type
+that does not include a prototype is called with arguments whose promoted
+types do not match those expected by the function.  When @option{-Wextra}
+is specified, also warn when a built-in function that takes arguments is
+declared without a prototype.  The @option{-Wno-builtin-declaration-mismatch}
+warning is enabled by default.  To avoid the warning include the appropriate
+header to bring the prototypes of built-in functions into scope.
+
+For example, the call to @code{memset} below is diagnosed by the warning
+because the function expects a value of type @code{size_t} as its argument
+but the type of @code{32} is @code{int}.  With @option{-Wextra},
+the declaration of the function is diagnosed as well.
+@smallexample
+extern void* memset ();
+void f (void *d)
+@{
+  memset (d, '\0', 32);
+@}
+@end smallexample
 
 @item -Wno-builtin-macro-redefined
 @opindex Wno-builtin-macro-redefined

gcc/testsuite/ChangeLog

+2018-11-15  Martin Sebor  <msebor@redhat.com>
+
+	PR c/83656
+	* gcc.dg/20021006-1.c
+	* gcc.dg/Wbuiltin-declaration-mismatch.c: New test.
+	* gcc.dg/Wbuiltin-declaration-mismatch-2.c: New test.
+	* gcc.dg/Wbuiltin-declaration-mismatch-3.c: New test.
+	* gcc.dg/Wbuiltin-declaration-mismatch-4.c: New test.
+	* gcc.dg/Walloca-16.c: Adjust.
+	* gcc.dg/Wrestrict-4.c: Adjust.
+	* gcc.dg/Wrestrict-5.c: Adjust.
+	* gcc.dg/atomic/stdatomic-generic.c: Adjust.
+	* gcc.dg/atomic/stdatomic-lockfree.c: Adjust.
+	* gcc.dg/initpri1.c: Adjust.
+	* gcc.dg/pr15698-1.c: Adjust.
+	* gcc.dg/pr69156.c: Adjust.
+	* gcc.dg/pr83463.c: Adjust.
+	* gcc.dg/redecl-4.c: Adjust.
+	* gcc.dg/tls/thr-init-2.c: Adjust.
+	* gcc.dg/torture/pr55890-2.c: Adjust.
+	* gcc.dg/torture/pr55890-3.c: Adjust.
+	* gcc.dg/torture/pr67741.c: Adjust.
+	* gcc.dg/torture/stackalign/sibcall-1.c: Adjust.
+	* gcc.dg/torture/tls/thr-init-1.c: Adjust.
+	* gcc.dg/tree-ssa/builtins-folding-gimple-ub.c: Adjust.
+
 2018-11-15  Nathan Sidwell  <nathan@acm.org>
 
 	PR c++/86246

gcc/testsuite/gcc.dg/20021006-1.c

@@ -2,7 +2,7 @@
    This testcase was miscompiled on x86-64 due to wrong access to the struct
    members.  */
 
-extern void abort();
+extern void abort(void);
 
 struct A {
   long x;

gcc/testsuite/gcc.dg/Walloca-16.c

@@ -5,3 +5,5 @@
 
 void *alloca ();
 __typeof__(alloca ()) a () { return alloca (); }
+
+/* { dg-prune-output "\\\[-Wbuiltin-declaration-mismatch]" } */

gcc/testsuite/gcc.dg/Wbuiltin-declaration-mismatch-2.c

+/* PR c/83656 - missing -Wbuiltin-declaration-mismatch on declaration
+   without prototype
+   { dg-do compile }
+   { dg-options "-Wall -Wextra" } */
+
+typedef __SIZE_TYPE__ size_t;
+
+/* Verify that ordinary library built-ins are not diagnosed with -Wextra
+   when they take no arguments (except in cases of return type mismatches).
+   This is in anticipation that C may some day adopt the same syntax as
+   C++ for declaring functions that take no arguments.  */
+
+void abort ();
+
+/* Verify that ordinary library built-ins are diagnosed with -Wextra
+   when they take arguments.  */
+
+void* memcpy ();    /* { dg-warning "declaration of built-in function .memcpy. without a prototype; expected .void \\\*\\\(void \\\*, const void \\\*, \(long \)*unsigned int\\\)." } */
+void* memset ();    /* { dg-warning "declaration of built-in function .memset. without a prototype; expected .void \\\*\\\(void \\\*, int, *\(long \)*unsigned int\\\)." } */
+size_t strlen ();   /* { dg-warning "declaration of built-in function .strlen. without a prototype; expected .\(long \)*unsigned int\\\(const char \\\*\\\)." } */
+
+/* Variadic built-ins are diagnosed even without -Wextra (they are,
+   in fact, diagnosed by default).  */
+int printf ();      /* { dg-warning "\\\[-Wbuiltin-declaration-mismatch]" } */
+int sprintf ();     /* { dg-warning "\\\[-Wbuiltin-declaration-mismatch]" } */

gcc/testsuite/gcc.dg/Wbuiltin-declaration-mismatch-3.c

+/* PR c/83656 - missing -Wbuiltin-declaration-mismatch on declaration
+   without prototype
+   { dg-do compile }
+   { dg-options "-Wbuiltin-declaration-mismatch" } */
+
+typedef __SIZE_TYPE__ size_t;
+
+/* Built-ins declared without a prototype are not diagnosed by default
+   (without -Wextra) except when their return type doesn't match.  */
+int abort ();       /* { dg-warning "\\\[-Wbuiltin-declaration-mismatch]" } */
+
+/* Built-ins declared without a prototype are not diagnosed without -Wextra.  */
+void exit ();
+void* memcpy ();
+void* memset ();
+
+
+void test_call_abort (void)
+{
+  /* Verify that a valid call to abort() is not diagnosed.  */
+  abort ();
+
+  /* Unfortunately, the incompatible declaration above makes GCC "forget"
+     that abort() is a built-in and so the invalid calls below aren't
+     diagnosed.  The only saving grace is that the invalid declaration
+     that differs in the return type is diagnosed by default. */
+  abort (1);        /* { dg-warning "too many arguments to built-in function .abort. expecting 0" "pr?????" { xfail *-*-* } } */
+
+  abort (1, 2);     /* { dg-warning "too many arguments" "pr?????" { xfail *-*-* } } */
+}
+
+
+void test_call_exit (void)
+{
+  /* Verify that valid calls to exit are not diagnosed.  */
+  exit ('\0');
+  exit (0);
+
+  /* Also verify calls to the built-in.  */
+  __builtin_exit ('\0');
+  __builtin_exit (0);
+  __builtin_exit (0.0);
+
+  exit ();          /* { dg-warning "too few arguments to built-in function 'exit' expecting 1" } */
+
+  exit (1, 2);      /* { dg-warning "too many arguments" } */
+
+  /* Verify that passing incompatible arguments triggers a warning.  */
+  exit ("");        /* { dg-warning "\\\[-Wint-conversion]" } */
+
+  struct S { int i; } s = { 0 };
+  exit (s);         /* { dg-warning "incompatible type for argument 1" } */
+}
+
+
+void test_call_memcpy (void *p, const void *q, size_t n)
+{
+  memcpy (p, q, n);
+
+  memcpy ();        /* { dg-warning "too few arguments to built-in function 'memcpy' expecting 3" } */
+
+  memcpy (p);       /* { dg-warning "too few arguments to built-in function 'memcpy' expecting 3" } */
+
+  memcpy (p, q);     /* { dg-warning "too few arguments to built-in function 'memcpy' expecting 3" } */
+
+  memcpy (q, p, n); /* { dg-warning "\\\[-Wdiscarded-qualifiers]" } */
+
+  memcpy (p, n, q); /* { dg-warning "\\\[-Wint-conversion]" } */
+
+  memcpy (p, q, n, 0); /* { dg-warning "too many arguments to built-in function 'memcpy' expecting 3" } */
+}
+
+
+typedef void* (memcpy_t)(void*, const void*, size_t);
+typedef void* (memset_t)(void*, int, size_t);
+
+void test_init (void)
+{
+  /* Verify that initialization of a pointer by the address of a built-in
+     function of a matching type declared without a prototype doesn't
+     trigger a warning...  */
+  memset_t *pmemset = memset;
+
+  /* ...but initialization by the address of an incompatible built-in
+     does even without -Wextra.  */
+  memcpy_t *pmemcpy = memset;           /* { dg-warning "\\\[-Wincompatible-pointer-types]" } */
+}
+
+
+void test_assign (void)
+{
+  /* Same as above but for assignment.  */
+  memset_t *pmemset;
+  pmemset = memset;
+
+  memcpy_t *pmemcpy;
+  pmemcpy = memset;                     /* { dg-warning "\\\[-Wincompatible-pointer-types]" } */
+}
+
+
+/* Verify that passing built-ins declared without a prototype to
+   functions that expect a pointer to a function of a specific type
+   is diagnosed.  Ditto for return statements.  */
+
+void take_memcpy (memcpy_t*);
+void take_any (int, ...);
+
+memset_t* pass_args (int i)
+{
+  take_memcpy (memcpy);
+  take_memcpy (memset);                 /* { dg-warning "\\\[-Wincompatible-pointer-types]" } */
+
+  take_any (0, i ? memcpy : memset);    /* { dg-warning "\\\[-Wincompatible-pointer-types]" } */
+
+  return memcpy;                        /* { dg-warning "\\\[-Wincompatible-pointer-types]" } */
+}

gcc/testsuite/gcc.dg/Wbuiltin-declaration-mismatch-4.c

+/* PR c/83656 - missing -Wbuiltin-declaration-mismatch on declaration
+   without prototype
+   { dg-do compile }
+   { dg-options "-Wbuiltin-declaration-mismatch" } */
+
+typedef __PTRDIFF_TYPE__ ptrdiff_t;
+typedef __SIZE_TYPE__    size_t;
+
+char c;
+signed char sc;
+unsigned char uc;
+short si;
+unsigned short usi;
+int i;
+unsigned ui;
+long li;
+unsigned long uli;
+
+size_t szi;
+typedef size_t SizeType;
+SizeType szti;
+
+ptrdiff_t diffi;
+
+enum E { e0 } e;
+
+float f;
+double d;
+long double ld;
+
+
+/* Verify warnings for undefined calls to built-ins expecting integer
+   arguments.  */
+
+int abs ();         /* { dg-message "built-in .abs. declared here" } */
+
+void test_integer_conversion_abs (void)
+{
+  i = abs (c);
+  i = abs (sc);
+  i = abs (uc);
+
+  i = abs (si);
+  i = abs (usi);
+
+  i = abs (i);
+  i = abs (ui);     /* { dg-warning ".abs. argument 1 type is .unsigned int. where .int. is expected in a call to built-in function declared without prototype" } */
+
+  /* Verify that the same call as above but to the built-in doesn't
+     trigger a warning.  */
+  i = __builtin_abs (ui);
+
+  i = abs (li);     /* { dg-warning ".abs. argument 1 type is .long int. where .int. is expected in a call to built-in function declared without prototype" } */
+  i = abs (uli);    /* { dg-warning ".abs. argument 1 type is .long unsigned int. where .int. is expected in a call to built-in function declared without prototype" } */
+
+  i = abs (e0);
+  i = abs (e);
+
+  i = abs (-1.0);   /* { dg-warning ".abs. argument 1 type is .double. where .int. is expected in a call to built-in function declared without prototype" } */
+  i = abs (f);      /* { dg-warning ".abs. argument 1 promotes to .double. where .int. is expected in a call to built-in function declared without prototype" } */
+  i = abs (ld);     /* { dg-warning ".abs. argument 1 type is .long double. where .int. is expected in a call to built-in function declared without prototype" } */
+
+  /* Verify that the same call as above but to the built-in doesn't
+     trigger a warning.  */
+  i = __builtin_abs (ld);
+}
+
+
+extern void* memset ();
+
+void test_integer_conversion_memset (void *d)
+{
+  memset (d, 0, sizeof (int));
+  memset (d, '\0', szi);
+  memset (d, i, szti);
+
+  /* Passing a ptrdiff_t where size_t is expected may not be unsafe
+     but because GCC may emits suboptimal code for such calls warning
+     for them helps improve efficiency.  */
+  memset (d, 0, diffi);       /* { dg-warning ".memset. argument 3 promotes to .ptrdiff_t. {aka .long int.} where .long unsigned int. is expected" } */
+
+  memset (d, 0, 2.0);         /* { dg-warning ".memset. argument 3 type is .double. where 'long unsigned int' is expected" } */
+
+  /* Verify that the same call as above but to the built-in doesn't
+     trigger a warning.  */
+  __builtin_memset (d, 0.0, 4.0);
+}
+
+
+/* Verify warnings for undefined calls to built-ins expecting floating
+   arguments.  */
+
+double fabs ();           /* { dg-message "built-in .fabs. declared here" } */
+
+/* Expect a warning for fabsf below because even a float argument promotes
+   to double.  Unfortunately, invalid calls to fabsf() are not diagnosed.  */
+float fabsf ();           /* { dg-warning "conflicting types for built-in function .fabsf.; expected .float\\\(float\\\)." } */
+long double fabsl ();     /* { dg-message "built-in .fabsl. declared here" } */
+
+void test_real_conversion_fabs (void)
+{
+  d = fabs (c);     /* { dg-warning ".fabs. argument 1 promotes to .int. where .double. is expected in a call to built-in function declared without prototype" } */
+
+  d = fabs (i);     /* { dg-warning ".fabs. argument 1 type is .int. where .double. is expected in a call to built-in function declared without prototype" } */
+
+  d = fabs (li);    /* { dg-warning ".fabs. argument 1 type is .long int. where .double. is expected in a call to built-in function declared without prototype" } */
+
+  /* In C, the type of an enumeration constant is int.  */
+  d = fabs (e0);    /* { dg-warning ".fabs. argument 1 type is .int. where .double. is expected in a call to built-in function declared without prototype" } */
+
+  d = fabs (e);     /* { dg-warning ".fabs. argument 1 type is .enum E. where .double. is expected in a call to built-in function declared without prototype" } */
+
+  /* No warning here since float is promoted to double.  */
+  d = fabs (f);
+
+  d = fabs (ld);    /* { dg-warning ".fabs. argument 1 type is .long double. where .double. is expected in a call to built-in function declared without prototype" } */
+
+  d = fabsf (c);    /* { dg-warning ".fabsf. argument 1 promotes to .int. where .float. is expected in a call to built-in function declared without prototype" "pr87890" { xfail *-*-* } } */
+
+  d = fabsl (c);    /* { dg-warning ".fabsl. argument 1 promotes to .int. where .long double. is expected in a call to built-in function declared without prototype" } */
+
+  d = fabsl (f);    /* { dg-warning ".fabsl. argument 1 promotes to .double. where .long double. is expected in a call to built-in function declared without prototype" } */
+
+  /* Verify that the same call as above but to the built-in doesn't
+     trigger a warning.  */
+  d = __builtin_fabsl (f);
+}
+
+/* Verify warnings for calls to a two-argument real function.  */
+
+double pow ();      /* { dg-message "built-in .pow. declared here" } */
+
+void test_real_conversion_pow (void)
+{
+  d = pow (2.0, 2.0);
+  d = pow (d, 3.0);
+  d = pow (d, d);
+
+  d = pow (2, 3.0); /* { dg-warning ".pow. argument 1 type is .int. where .double. is expected in a call to built-in function declared without prototype" } */
+  d = pow (3.0, 2); /* { dg-warning ".pow. argument 2 type is .int. where .double. is expected in a call to built-in function declared without prototype" } */
+}
+
+
+/* Verify warnings for calls that discard qualifiers.  */
+
+extern void* memcpy ();
+
+void test_qual_conversion_memcpy (void *d, const void *s)
+{
+  memcpy (d, s, sizeof (int));
+  memcpy (s, d, sizeof (int));    /* { dg-warning "passing argument 1 of .memcpy. discards 'const' qualifier from pointer target type" } */
+}

gcc/testsuite/gcc.dg/Wbuiltin-declaration-mismatch.c

+/* PR c/83656 - missing -Wbuiltin-declaration-mismatch on declaration
+   without prototype
+   { dg-do compile }
+   { dg-options "-Wall" } */
+
+typedef __SIZE_TYPE__ size_t;
+
+/* Verify that ordinary library built-ins are not diagnosed with -Wall
+   (or by default) whether or not they take arguments (even though they
+   should be).  */
+
+void abort ();
+void* memcpy ();
+void* memset ();
+size_t strlen ();
+
+/* Verify mismatches in return types are diagnosed.  */
+int exit ();        /* { dg-warning "\\\[-Wbuiltin-declaration-mismatch]" } */
+
+/* Variadic built-ins are diagnosed with -Wall (they are, in fact,
+   diagnosed by default).  */
+int printf ();      /* { dg-warning "\\\[-Wbuiltin-declaration-mismatch]" } */
+int sprintf ();     /* { dg-warning "\\\[-Wbuiltin-declaration-mismatch]" } */

gcc/testsuite/gcc.dg/Wrestrict-4.c

@@ -109,3 +109,5 @@ void* test_strncpy_2 (char *d, const char *s)
 {
   return strncpy (d, s);
 }
+
+/* { dg-prune-output "\\\[-Wbuiltin-declaration-mismatch]" } */

gcc/testsuite/gcc.dg/Wrestrict-5.c

@@ -42,3 +42,6 @@ void test_strncpy_nowarn (char *d)
 {
   strncpy (d + 1, d + 3, "");
 }
+
+/* { dg-prune-output "\\\[-Wbuiltin-declaration-mismatch]" }
+   { dg-prune-output "\\\[-Wint-conversion]" } */

gcc/testsuite/gcc.dg/atomic/stdatomic-generic.c

@@ -4,7 +4,7 @@
 
 #include <stdatomic.h>
 
-extern void abort ();
+extern void abort (void);
 extern int memcmp (const void *, const void *, __SIZE_TYPE__);
 
 typedef struct test {

gcc/testsuite/gcc.dg/atomic/stdatomic-lockfree.c

@@ -5,7 +5,7 @@
 #include <stdatomic.h>
 #include <stdint.h>
 
-extern void abort ();
+extern void abort (void);
 
 _Atomic _Bool aba;
 atomic_bool abt;

gcc/testsuite/gcc.dg/initpri1.c

 /* { dg-do run { target init_priority } } */
 
-extern void abort ();
+extern void abort (void);
 
 int i;
 int j;

gcc/testsuite/gcc.dg/pr15698-1.c

@@ -21,3 +21,5 @@ char *rindex(a, b)
 {
   return 0;
 }
+
+/* { dg-prune-output "\\\[-Wbuiltin-declaration-mismatch]" } */

gcc/testsuite/gcc.dg/pr69156.c

@@ -5,6 +5,6 @@
 _Bool
 foo ()
 {
-  _Bool (*f) () = __builtin_abs;	/* { dg-warning "initialization of '_Bool \\(\\*\\)\\(\\)' from incompatible pointer type" } */
+  _Bool (*f) () = __builtin_abs;	/* { dg-warning "initialization of '_Bool \\(\\*\\)\\(\\)' from pointer to .__builtin_abs. with incompatible type .int \\\(\\\*\\\)." } */
   return f (0);
 }

gcc/testsuite/gcc.dg/pr83463.c

@@ -16,3 +16,5 @@ p ()
 {
   m (p + (long) a);
 }
+
+/* { dg-prune-output "\\\[-Wbuiltin-declaration-mismatch]" } */

gcc/testsuite/gcc.dg/redecl-4.c

@@ -27,3 +27,6 @@ f (void)
 
 /* Should still diagnose incompatible prototype for strcmp.  */
 int strcmp (void); /* { dg-error "conflict" } */
+
+/* { dg-prune-output "\\\[-Wbuiltin-declaration-mismatch]" }
+   { dg-prune-output "\\\[-Wint-conversion]" } */

gcc/testsuite/gcc.dg/tls/thr-init-2.c

@@ -2,7 +2,7 @@
 /* { dg-require-effective-target tls_runtime } */
 /* { dg-add-options tls } */
 
-extern void abort() ;
+extern void abort (void);
 
 static __thread int fstat ;
 static __thread int fstat = 1;

gcc/testsuite/gcc.dg/torture/pr55890-2.c

@@ -3,3 +3,5 @@
 
 extern void *memcpy();
 int main() { memcpy(); }
+
+/* { dg-prune-output "\\\[-Wbuiltin-declaration-mismatch]" } */

gcc/testsuite/gcc.dg/torture/pr55890-3.c

@@ -8,3 +8,5 @@ bar ()
 {
   return memmove ();
 }
+
+/* { dg-prune-output "\\\[-Wbuiltin-declaration-mismatch]" } */

gcc/testsuite/gcc.dg/torture/pr67741.c

@@ -9,5 +9,6 @@ float cabsf(fc)
 {
   struct doublecomplex dc ;
   dc.real=fc.real; dc.imag=fc.imag;
-  return (float) cabs(dc);
+  return (float) cabs(dc);   /* { dg-warning "incompatible type for argument 1 of .cabs." } */
 }
+

gcc/testsuite/gcc.dg/torture/pr71816.c

 /* { dg-do compile } */
-/* { dg-prune-output "conflicting types for built-in" } */
+/* { dg-prune-output "\\\[-Wbuiltin-declaration-mismatch" } */
 
 void *ext2fs_resize_mem_p;
 struct ext2_icount_el {

gcc/testsuite/gcc.dg/torture/stackalign/sibcall-1.c

 /* { dg-do run } */
 
 extern int ok (int);
-extern void exit ();
+extern void exit (int);
 static int gen_x86_64_shrd (int);
 static int
 gen_x86_64_shrd(int a __attribute__ ((__unused__)))

gcc/testsuite/gcc.dg/torture/tls/thr-init-1.c

@@ -3,7 +3,7 @@
 /* { dg-add-options tls } */
 
 extern int printf (char *,...);
-extern void abort() ;
+extern void abort(void) ;
 
 int test_code(int b)
 {

gcc/testsuite/gcc.dg/tree-ssa/builtins-folding-gimple-ub.c

@@ -31,4 +31,5 @@ main (void)
   return 0;
 }
 
-/* { dg-final { scan-tree-dump-times "__builtin_memchr" 2 "optimized" } } */
+/* { dg-prune-output "-Wbuiltin-declaration-mismatch" }
+   { dg-final { scan-tree-dump-times "__builtin_memchr" 2 "optimized" } } */