2007-09-23  Jakub Jelinek  <jakub@redhat.com>

	* expr.c (expand_expr_real_1) <case CALL_EXPR>: Use get_callee_fndecl
	instead of checking CALL_EXPR_FN directly to test for builtins.
	If error or warning attributes are present, print
	error resp. warning.
	* c-common.c (handle_error_attribute): New function.
	(c_common_attribute_table): Add error and warning
	attributes.
	* doc/extend.texi: Document error and warning attributes.

	* gcc.dg/va-arg-pack-len-1.c: Use error and warning
	attributes.
	* gcc.dg/va-arg-pack-len-2.c: New test.
	* g++.dg/ext/va-arg-pack-len-1.C: Use error and warning
	attributes.
	* g++.dg/ext/va-arg-pack-len-2.C: New test.

--- gcc/doc/extend.texi.jj	2007-09-25 15:04:15.000000000 +0200
+++ gcc/doc/extend.texi	2007-09-25 15:32:22.000000000 +0200
@@ -1589,8 +1589,8 @@ attributes are currently defined for fun
 @code{section}, @code{constructor}, @code{destructor}, @code{used},
 @code{unused}, @code{deprecated}, @code{weak}, @code{malloc},
 @code{alias}, @code{warn_unused_result}, @code{nonnull},
-@code{gnu_inline}, @code{externally_visible} and @code{artificial}.
-Several other
+@code{gnu_inline}, @code{externally_visible}, @code{artificial},
+@code{error} and @code{warning}.  Several other
 attributes are defined for functions on particular target systems.  Other
 attributes, including @code{section} are supported for variables declarations
 (@pxref{Variable Attributes}) and for types (@pxref{Type Attributes}).
@@ -1688,6 +1688,30 @@ Whether the function itself is considere
 the current inlining parameters.  The @code{flatten} attribute only works
 reliably in unit-at-a-time mode.
 
+@item error ("@var{message}")
+@cindex @code{error} function attribute
+If this attribute is used on a function declaration and a call to such a function
+is not eliminated through dead code elimination or other optimizations, an error
+which will include @var{message} will be diagnosed.  This is useful
+for compile time checking, especially together with @code{__builtin_constant_p}
+and inline functions where checking the inline function arguments is not
+possible through @code{extern char [(condition) ? 1 : -1];} tricks.
+While it is possible to leave the function undefined and thus invoke
+a link failure, when using this attribute the problem will be diagnosed
+earlier and with exact location of the call even in presence of inline
+functions or when not emitting debugging information.
+
+@item warning ("@var{message}")
+@cindex @code{warning} function attribute
+If this attribute is used on a function declaration and a call to such a function
+is not eliminated through dead code elimination or other optimizations, a warning
+which will include @var{message} will be diagnosed.  This is useful
+for compile time checking, especially together with @code{__builtin_constant_p}
+and inline functions.  While it is possible to define the function with
+a message in @code{.gnu.warning*} section, when using this attribute the problem
+will be diagnosed earlier and with exact location of the call even in presence
+of inline functions or when not emitting debugging information.
+
 @item cdecl
 @cindex functions that do pop the argument stack on the 386
 @opindex mrtd
--- gcc/expr.c.jj	2007-09-25 14:58:40.000000000 +0200
+++ gcc/expr.c	2007-09-25 15:19:15.000000000 +0200
@@ -7513,19 +7513,31 @@ expand_expr_real_1 (tree exp, rtx target
 	 inlining.  */
       if (CALL_EXPR_VA_ARG_PACK (exp))
 	error ("invalid use of %<__builtin_va_arg_pack ()%>");
-      /* Check for a built-in function.  */
-      if (TREE_CODE (TREE_OPERAND (exp, 0)) == ADDR_EXPR
-	  && (TREE_CODE (TREE_OPERAND (TREE_OPERAND (exp, 0), 0))
-	      == FUNCTION_DECL)
-	  && DECL_BUILT_IN (TREE_OPERAND (TREE_OPERAND (exp, 0), 0)))
-	{
-	  if (DECL_BUILT_IN_CLASS (TREE_OPERAND (TREE_OPERAND (exp, 0), 0))
-	      == BUILT_IN_FRONTEND)
-	    return lang_hooks.expand_expr (exp, original_target,
-					   tmode, modifier,
-					   alt_rtl);
-	  else
-	    return expand_builtin (exp, target, subtarget, tmode, ignore);
+      {
+	tree fndecl = get_callee_fndecl (exp), attr;
+
+	if (fndecl
+	    && (attr = lookup_attribute ("error",
+					 DECL_ATTRIBUTES (fndecl))) != NULL)
+	  error ("call to %qs declared with attribute error: %s",
+		 lang_hooks.decl_printable_name (fndecl, 1),
+		 TREE_STRING_POINTER (TREE_VALUE (TREE_VALUE (attr))));
+	if (fndecl
+	    && (attr = lookup_attribute ("warning",
+					 DECL_ATTRIBUTES (fndecl))) != NULL)
+	  warning (0, "call to %qs declared with attribute warning: %s",
+		   lang_hooks.decl_printable_name (fndecl, 1),
+		   TREE_STRING_POINTER (TREE_VALUE (TREE_VALUE (attr))));
+
+	/* Check for a built-in function.  */
+	if (fndecl && DECL_BUILT_IN (fndecl))
+	  {
+	    if (DECL_BUILT_IN_CLASS (fndecl) == BUILT_IN_FRONTEND)
+	      return lang_hooks.expand_expr (exp, original_target,
+					     tmode, modifier, alt_rtl);
+	    else
+	      return expand_builtin (exp, target, subtarget, tmode, ignore);
+	  }
 	}
 
       return expand_call (exp, target, ignore);
--- gcc/c-common.c.jj	2007-09-25 15:01:49.000000000 +0200
+++ gcc/c-common.c	2007-09-25 15:24:34.000000000 +0200
@@ -508,6 +508,7 @@ static tree handle_always_inline_attribu
 static tree handle_gnu_inline_attribute (tree *, tree, tree, int, bool *);
 static tree handle_artificial_attribute (tree *, tree, tree, int, bool *);
 static tree handle_flatten_attribute (tree *, tree, tree, int, bool *);
+static tree handle_error_attribute (tree *, tree, tree, int, bool *);
 static tree handle_used_attribute (tree *, tree, tree, int, bool *);
 static tree handle_unused_attribute (tree *, tree, tree, int, bool *);
 static tree handle_externally_visible_attribute (tree *, tree, tree, int,
@@ -641,6 +642,10 @@ const struct attribute_spec c_common_att
 			      handle_warn_unused_result_attribute },
   { "sentinel",               0, 1, false, true, true,
 			      handle_sentinel_attribute },
+  { "warning",		      1, 1, true,  false, false,
+			      handle_error_attribute },
+  { "error",		      1, 1, true,  false, false,
+			      handle_error_attribute },
   { NULL,                     0, 0, false, false, false, NULL }
 };
 
@@ -4226,6 +4231,26 @@ handle_flatten_attribute (tree *node, tr
   return NULL_TREE;
 }
 
+/* Handle a "warning" or "error" attribute; arguments as in
+   struct attribute_spec.handler.  */
+
+static tree
+handle_error_attribute (tree *node, tree name, tree args,
+			int ARG_UNUSED (flags), bool *no_add_attrs)
+{
+  if (TREE_CODE (*node) == FUNCTION_DECL
+      || TREE_CODE (TREE_VALUE (args)) == STRING_CST)
+    /* Do nothing else, just set the attribute.  We'll get at
+       it later with lookup_attribute.  */
+    ;
+  else
+    {
+      warning (OPT_Wattributes, "%qE attribute ignored", name);
+      *no_add_attrs = true;
+    }
+
+  return NULL_TREE;
+}
 
 /* Handle a "used" attribute; arguments as in
    struct attribute_spec.handler.  */
--- gcc/testsuite/gcc.dg/va-arg-pack-len-1.c.jj	2007-09-25 12:23:05.000000000 +0200
+++ gcc/testsuite/gcc.dg/va-arg-pack-len-1.c	2007-09-25 15:16:03.000000000 +0200
@@ -3,8 +3,10 @@
 
 #include <stdarg.h>
 
-extern int warn_open_missing_mode (void);
-extern int warn_open_too_many_arguments (void);
+extern int error_open_missing_mode (void)
+  __attribute__((__error__ ("open with O_CREAT needs 3 arguments, only 2 were given")));
+extern int warn_open_too_many_arguments (void)
+  __attribute__((__warning__ ("open called with more than 3 arguments")));
 extern void abort (void);
 
 char expected_char;
@@ -83,7 +85,7 @@ myopen (const char *path, int oflag, ...
     {
       if ((oflag & 0x40) != 0 && __builtin_va_arg_pack_len () < 1)
 	{
-	  warn_open_missing_mode ();
+	  error_open_missing_mode ();
 	  return myopen2 (path, oflag);
 	}
       return myopenva (path, oflag, __builtin_va_arg_pack ());
--- gcc/testsuite/gcc.dg/va-arg-pack-len-2.c.jj	2007-09-25 15:16:03.000000000 +0200
+++ gcc/testsuite/gcc.dg/va-arg-pack-len-2.c	2007-09-25 15:16:03.000000000 +0200
@@ -0,0 +1,42 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+#include <stdarg.h>
+
+extern int error_open_missing_mode (void)
+  __attribute__((__error__ ("open with O_CREAT needs 3 arguments, only 2 were given")));
+extern int warn_open_too_many_arguments (void)
+  __attribute__((__warning__ ("open called with more than 3 arguments")));
+
+extern int myopen2 (const char *path, int oflag);
+extern int myopenva (const char *path, int oflag, ...);
+
+extern inline __attribute__((always_inline, gnu_inline)) int
+myopen (const char *path, int oflag, ...)
+{
+  if (__builtin_va_arg_pack_len () > 1)
+    warn_open_too_many_arguments ();	/* { dg-warning "called with more than 3" } */
+
+  if (__builtin_constant_p (oflag))
+    {
+      if ((oflag & 0x40) != 0 && __builtin_va_arg_pack_len () < 1)
+	{
+	  error_open_missing_mode ();	/* { dg-error "needs 3 arguments, only 2 were given" } */
+	  return myopen2 (path, oflag);
+	}
+      return myopenva (path, oflag, __builtin_va_arg_pack ());
+    }
+
+  if (__builtin_va_arg_pack_len () < 1)
+    return myopen2 (path, oflag);
+
+  return myopenva (path, oflag, __builtin_va_arg_pack ());
+}
+
+int
+main (void)
+{
+  myopen ("h", 0x43);
+  myopen ("i", 0x43, 0644, 0655);
+  return 0;
+}
--- gcc/testsuite/g++.dg/ext/va-arg-pack-len-1.C.jj	2007-09-25 12:23:05.000000000 +0200
+++ gcc/testsuite/g++.dg/ext/va-arg-pack-len-1.C	2007-09-25 15:16:03.000000000 +0200
@@ -3,8 +3,10 @@
 
 #include <stdarg.h>
 
-extern "C" int warn_open_missing_mode (void);
-extern "C" int warn_open_too_many_arguments (void);
+extern "C" int error_open_missing_mode (void)
+  __attribute__((__error__ ("open with O_CREAT needs 3 arguments, only 2 were given")));
+extern "C" int warn_open_too_many_arguments (void)
+  __attribute__((__warning__ ("open called with more than 3 arguments")));
 extern "C" void abort (void);
 
 char expected_char;
@@ -83,7 +85,7 @@ myopen (const char *path, int oflag, ...
     {
       if ((oflag & 0x40) != 0 && __builtin_va_arg_pack_len () < 1)
 	{
-	  warn_open_missing_mode ();
+	  error_open_missing_mode ();
 	  return myopen2 (path, oflag);
 	}
       return myopenva (path, oflag, __builtin_va_arg_pack ());
--- gcc/testsuite/g++.dg/ext/va-arg-pack-len-2.C.jj	2007-09-25 15:16:03.000000000 +0200
+++ gcc/testsuite/g++.dg/ext/va-arg-pack-len-2.C	2007-09-25 15:16:03.000000000 +0200
@@ -0,0 +1,42 @@
+// { dg-do compile }
+// { dg-options "-O2" }
+
+#include <stdarg.h>
+
+extern int error_open_missing_mode (void)
+  __attribute__((__error__ ("open with O_CREAT needs 3 arguments, only 2 were given")));
+extern int warn_open_too_many_arguments (void)
+  __attribute__((__warning__ ("open called with more than 3 arguments")));
+
+extern int myopen2 (const char *path, int oflag);
+extern int myopenva (const char *path, int oflag, ...);
+
+extern inline __attribute__((always_inline, gnu_inline)) int
+myopen (const char *path, int oflag, ...)
+{
+  if (__builtin_va_arg_pack_len () > 1)
+    warn_open_too_many_arguments ();	// { dg-warning "called with more than 3" }
+
+  if (__builtin_constant_p (oflag))
+    {
+      if ((oflag & 0x40) != 0 && __builtin_va_arg_pack_len () < 1)
+	{
+	  error_open_missing_mode ();	// { dg-error "needs 3 arguments, only 2 were given" }
+	  return myopen2 (path, oflag);
+	}
+      return myopenva (path, oflag, __builtin_va_arg_pack ());
+    }
+
+  if (__builtin_va_arg_pack_len () < 1)
+    return myopen2 (path, oflag);
+
+  return myopenva (path, oflag, __builtin_va_arg_pack ());
+}
+
+int
+main (void)
+{
+  myopen ("h", 0x43);
+  myopen ("i", 0x43, 0644, 0655);
+  return 0;
+}