re PR middle-end/87053 (wrong code with c_strlen)

gcc:
2018-08-22  Bernd Edlinger  <bernd.edlinger@hotmail.de>

	PR middle-end/87053
	* builtins.c (c_strlen): Improve range checks.

testsuite:
2018-08-22  Bernd Edlinger  <bernd.edlinger@hotmail.de>

	PR middle-end/87053
	* gcc.c-torture/execute/pr87053.c: New test.

From-SVN: r263968

gcc/ChangeLog

+2018-08-29  Bernd Edlinger  <bernd.edlinger@hotmail.de>
+
+	PR middle-end/87053
+	* builtins.c (c_strlen): Improve range checks.
+
 2018-08-29  Martin Sebor  <msebor@redhat.com>
 	    Jeff Law  <law@redhat.com>
 

gcc/builtins.c

@@ -567,7 +567,7 @@ string_length (const void *ptr, unsigned eltsize, unsigned maxelts)
 tree
 c_strlen (tree src, int only_value, unsigned eltsize)
 {
-  gcc_assert (eltsize == 1 || eltsize == 2 || eltsize == 4);
+  gcc_checking_assert (eltsize == 1 || eltsize == 2 || eltsize == 4);
   STRIP_NOPS (src);
   if (TREE_CODE (src) == COND_EXPR
       && (only_value || !TREE_SIDE_EFFECTS (TREE_OPERAND (src, 0))))
@@ -656,10 +656,10 @@ c_strlen (tree src, int only_value, unsigned eltsize)
      a null character if we can represent it as a single HOST_WIDE_INT.  */
   if (byteoff == 0)
     eltoff = 0;
-  else if (! tree_fits_shwi_p (byteoff))
+  else if (! tree_fits_uhwi_p (byteoff) || tree_to_uhwi (byteoff) % eltsize)
     eltoff = -1;
   else
-    eltoff = tree_to_shwi (byteoff) / eltsize;
+    eltoff = tree_to_uhwi (byteoff) / eltsize;
 
   /* If the offset is known to be out of bounds, warn, and call strlen at
      runtime.  */
@@ -691,6 +691,11 @@ c_strlen (tree src, int only_value, unsigned eltsize)
   unsigned len = string_length (ptr + eltoff * eltsize, eltsize,
 				strelts - eltoff);
 
+  /* Don't know what to return if there was no zero termination. 
+     Ideally this would turn into a gcc_checking_assert over time.  */
+  if (len > maxelts - eltoff)
+    return NULL_TREE;
+
   return ssize_int (len);
 }
 

gcc/testsuite/ChangeLog

+2018-08-29  Bernd Edlinger  <bernd.edlinger@hotmail.de>
+
+	PR middle-end/87053
+	* gcc.c-torture/execute/pr87053.c: New test.
+
 2018-08-29  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/87095

gcc/testsuite/gcc.c-torture/execute/pr87053.c

+/* PR middle-end/87053 */
+
+const union
+{ struct {
+    char x[4];
+    char y[4];
+  };
+  struct {
+    char z[8];
+  };
+} u = {{"1234", "567"}};
+
+int main ()
+{
+  if (__builtin_strlen (u.z) != 7)
+    __builtin_abort ();
+}