Make sure that statements such as:

  strcpy (dst, "/gnu/store/…");

do not result in chunked /gnu/store strings that are undetectable by
Guix's GC and its grafting code.  See <http://bugs.gnu.org/24703>.

--- gcc-5.3.0/gcc/builtins.c	2016-10-18 10:50:46.080616285 +0200
+++ gcc-5.3.0/gcc/builtins.c	2016-11-09 15:26:43.693042737 +0100
@@ -3192,6 +3192,42 @@ determine_block_size (tree len, rtx len_
 			  GET_MODE_MASK (GET_MODE (len_rtx)));
 }
 
+/* Return true if STR contains the string "/gnu/store".  */
+
+static bool
+store_reference_p (tree str)
+{
+  if (TREE_CODE (str) == ADDR_EXPR)
+    str = TREE_OPERAND (str, 0);
+
+  if (TREE_CODE (str) != STRING_CST)
+    return false;
+
+  int len;
+  const char *store;
+
+  store = getenv ("NIX_STORE") ? getenv ("NIX_STORE") : "/gnu/store";
+  len = strlen (store);
+
+  /* Size of the hash part of store file names, including leading slash and
+     trailing hyphen.  */
+  const int</td></tr></table>
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