re PR middle-end/86121 (missing -Wstringop-overflow on strcpy followed by strcat)

2018-08-21  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        PR middle-end/86121
        * tree-ssa-strlen.c (adjust_last_stmt): Avoid folding away undefined
        behaviour.

testsuite:
2018-08-21  Bernd Edlinger  <bernd.edlinger@hotmail.de>

        PR middle-end/86121
        * gcc.dg/Wstringop-overflow-6.c: Remove xfail.

From-SVN: r263693

gcc/ChangeLog

+2018-08-21  Bernd Edlinger  <bernd.edlinger@hotmail.de>
+
+	PR middle-end/86121
+	* tree-ssa-strlen.c (adjust_last_stmt): Avoid folding away undefined
+	behaviour.
+
 2018-08-21  Rasmus Villemoes  <rv@rasmusvillemoes.dk>
 
 	* config/vxworks.h: Guard vxworks_asm_out_constructor and

gcc/testsuite/ChangeLog

+2018-08-21  Bernd Edlinger  <bernd.edlinger@hotmail.de>
+
+	PR middle-end/86121
+	* gcc.dg/Wstringop-overflow-6.c: Remove xfail.
+
 2018-08-21  Tom de Vries  <tdevries@suse.de>
 
 	* gcc.c-torture/unsorted/dump-noaddr.x: Use -gno-record-gcc-switches

gcc/testsuite/gcc.dg/Wstringop-overflow-6.c

@@ -25,7 +25,7 @@ void test_strcpy_strcat_1 (void)
 
 void test_strcpy_strcat_2 (void)
 {
-  strcpy (a2, "12"), strcat (a2, "3");   /* { dg-warning "\\\[-Wstringop-overflow=]" "bug 86121" { xfail *-*-* } } */
+  strcpy (a2, "12"), strcat (a2, "3");   /* { dg-warning "\\\[-Wstringop-overflow=]" } */
 }
 
 void test_strcpy_strcat_3 (void)

gcc/tree-ssa-strlen.c

@@ -1107,6 +1107,13 @@ adjust_last_stmt (strinfo *si, gimple *stmt, bool is_strcat)
 	 to store the extra '\0' in that case.  */
       if ((tree_to_uhwi (len) & 3) == 0)
 	return;
+
+      /* Don't fold away an out of bounds access, as this defeats proper
+	 warnings.  */
+      tree dst = gimple_call_arg (last.stmt, 0);
+      tree size = compute_objsize (dst, 0);
+      if (size && tree_int_cst_lt (size, len))
+	return;
     }
   else if (TREE_CODE (len) == SSA_NAME)
     {