c-common.c (check_format_types): Check for writing through a NULL pointer argument.

	* c-common.c (check_format_types): Check for writing through a
	NULL pointer argument.

testsuite:
	* gcc.dg/c90-printf-1.c, gcc.dg/c90-scanf-1.c: Add tests for
	writing through null pointers; remove comment about testing
	unterminated strings.

From-SVN: r36936

gcc/ChangeLog

+2000-10-18  Joseph S. Myers  <jsm28@cam.ac.uk>
+
+	* c-common.c (check_format_types): Check for writing through a
+	NULL pointer argument.
+
 2000-10-18  Hans-Peter Nilsson  <hp@axis.com>
 
 	* tm.texi (Exception Region Output): Document

gcc/c-common.c

@@ -3119,6 +3119,15 @@ check_format_types (status, types)
 	      if (TREE_CODE (cur_type) == ERROR_MARK)
 		break;
 
+	      /* Check for writing through a NULL pointer.  */
+	      if (types->writing_in_flag
+		  && i == 0
+		  && cur_param != 0
+		  && integer_zerop (cur_param))
+		status_warning (status,
+				"writing through null pointer (arg %d)",
+				arg_num);
+
 	      if (cur_param != 0 && TREE_CODE (cur_param) == ADDR_EXPR)
 		cur_param = TREE_OPERAND (cur_param, 0);
 	      else

gcc/testsuite/ChangeLog

+2000-10-18  Joseph S. Myers  <jsm28@cam.ac.uk>
+
+	* gcc.dg/c90-printf-1.c, gcc.dg/c90-scanf-1.c: Add tests for
+	writing through null pointers; remove comment about testing
+	unterminated strings.
+
 2000-10-17  Matthew Hiller  <hiller@redhat.com>
 
 	* gcc.c-torture/execute/20001017-2.c: New test.

gcc/testsuite/gcc.dg/c90-printf-1.c

@@ -244,5 +244,5 @@ foo (int i, int i1, int i2, unsigned int u, double d, char *s, void *p,
   printf ("%++d", i); /* { dg-warning "repeated" "repeated flag warning" } */
   printf ("%n", cn); /* { dg-warning "constant" "%n with const" } */
   printf ((const char *)L"foo"); /* { dg-warning "wide" "wide string" } */
-  /* Can we test for the warning for unterminated string formats?  */
+  printf ("%n", (int *)0); /* { dg-warning "null" "%n with NULL" } */
 }

gcc/testsuite/gcc.dg/c90-scanf-1.c

@@ -122,4 +122,5 @@ foo (int *ip, unsigned int *uip, short int *hp, unsigned short int *uhp,
   scanf ("%d\0%d", ip, ip); /* { dg-warning "embedded|too many" "warning for embedded NUL" } */
   scanf (NULL); /* { dg-warning "null" "null format string warning" } */
   scanf ("%"); /* { dg-warning "trailing" "trailing % warning" } */
+  scanf ("%d", (int *)0); /* { dg-warning "null" "writing into NULL" } */
 }