PR middle-end/80669 - Bad -Wstringop-overflow warnings for stpncpy

gcc/ChangeLog:

	PR middle-end/80669
	* builtins.c (expand_builtin_stpncpy): Simplify.

gcc/testsuite/ChangeLog:

	PR middle-end/80669
	* gcc.dg/builtin-stpncpy.c: New test.

From-SVN: r248034

gcc/ChangeLog

+2017-05-14  Martin Sebor  <msebor@redhat.com>
+
+	PR middle-end/80669
+	* builtins.c (expand_builtin_stpncpy): Simplify.
+
 2017-05-14  Daniel Santos  <daniel.santos@pobox.com>
 
 	* config/i386/i386.opt: Add option -mcall-ms2sysv-xlogues.

gcc/builtins.c

@@ -3788,31 +3788,18 @@ expand_builtin_stpncpy (tree exp, rtx)
       || !warn_stringop_overflow)
     return NULL_RTX;
 
+  /* The source and destination of the call.  */
   tree dest = CALL_EXPR_ARG (exp, 0);
   tree src = CALL_EXPR_ARG (exp, 1);
 
-  /* The number of bytes to write (not the maximum).  */
+  /* The exact number of bytes to write (not the maximum).  */
   tree len = CALL_EXPR_ARG (exp, 2);
-  /* The length of the source sequence.  */
-  tree slen = c_strlen (src, 1);
-
-  /* Try to determine the range of lengths that the source expression
-     refers to.  */
-  tree lenrange[2];
-  if (slen)
-    lenrange[0] = lenrange[1] = slen;
-  else
-    {
-      get_range_strlen (src, lenrange);
-      slen = lenrange[0];
-    }
 
+  /* The size of the destination object.  */
   tree destsize = compute_objsize (dest, warn_stringop_overflow - 1);
 
-  /* The number of bytes to write is LEN but check_sizes will also
-     check SLEN if LEN's value isn't known.  */
   check_sizes (OPT_Wstringop_overflow_,
-	       exp, len, /*maxlen=*/NULL_TREE, slen, destsize);
+	       exp, len, /*maxlen=*/NULL_TREE, src, destsize);
 
   return NULL_RTX;
 }

gcc/testsuite/ChangeLog

+2017-05-14  Martin Sebor  <msebor@redhat.com>
+
+	PR middle-end/80669
+	* gcc.dg/builtin-stpncpy.c: New test.
+
 2017-05-14  Daniel Santos  <daniel.santos@pobox.com>
 
 	* gcc.target/x86_64/abi/ms-sysv/do-test.S: New file.

gcc/testsuite/gcc.dg/builtin-stpncpy.c

+/* PR tree-optimization/80669 - Bad -Wstringop-overflow warnings for stpncpy
+   { dg-do compile }
+   { dg-options "-O2 -Wall" } */
+
+#define SIZE_MAX __SIZE_MAX__
+
+typedef __SIZE_TYPE__ size_t;
+
+void sink (char*);
+
+#define stpncpy (d, s, n)  sink (__builtin_stpncpy (d, s, n))
+
+size_t value (void);
+
+size_t range (size_t min, size_t max)
+{
+  size_t val = value ();
+  return val < min || max < val ? min : val;
+}
+
+/* Verify that no warning is issued for stpncpy with constant size.  */
+void test_cst (char *d)
+{
+  __builtin_stpncpy (d, "123", 0);
+  __builtin_stpncpy (d, "123", 1);
+  __builtin_stpncpy (d, "123", 2);
+  __builtin_stpncpy (d, "123", 3);
+  __builtin_stpncpy (d, "123", 4);
+  __builtin_stpncpy (d, "123", 5);
+  __builtin_stpncpy (d, "123", 999);
+
+  size_t n = SIZE_MAX / 2;
+
+  __builtin_stpncpy (d, "123", n);
+
+  __builtin_stpncpy (d, "123", n + 1);    /* { dg-warning "specified size \[0-9\]+ exceeds maximum object size \[0-9\]+" } */
+}
+
+
+/* Verify that no warning is issued for stpncpy with size in some range.  */
+void test_rng (char *d)
+{
+#define R(min, max) range (min, max)
+
+  __builtin_stpncpy (d, "123", R (0, 1));
+  __builtin_stpncpy (d, "123", R (0, 2));
+  __builtin_stpncpy (d, "123", R (0, 3));
+  __builtin_stpncpy (d, "123", R (0, 4));
+  __builtin_stpncpy (d, "123", R (0, 5));
+
+  __builtin_stpncpy (d, "123", R (1, 2));
+  __builtin_stpncpy (d, "123", R (1, 3));
+  __builtin_stpncpy (d, "123", R (1, 4));
+  __builtin_stpncpy (d, "123", R (1, 5));
+
+  __builtin_stpncpy (d, "123", R (2, 3));
+  __builtin_stpncpy (d, "123", R (2, 4));
+  __builtin_stpncpy (d, "123", R (2, 5));
+
+  __builtin_stpncpy (d, "123", R (3, 4));
+  __builtin_stpncpy (d, "123", R (3, 5));
+
+  __builtin_stpncpy (d, "123", R (4, 5));
+
+  __builtin_stpncpy (d, "123", R (5, 6));
+
+  __builtin_stpncpy (d, "123", R (12345, 23456));
+
+  size_t n = SIZE_MAX / 2;
+
+  __builtin_stpncpy (d, "123", R (n - 1, n + 1));
+
+  __builtin_stpncpy (d, "123", R (n + 1, n + 2));   /* { dg-warning "specified size between \[0-9\]+ and \[0-9\]+ exceeds maximum object size \[0-9\]+" } */
+}