Make sure that statements such as:

  strcpy (dst, "/gnu/store/…");

or

  static const char str[] = "/gnu/store/…";
  …
  strcpy (dst, str);

do not result in chunked /gnu/store strings that are undetectable by
Guix's GC and its grafting code.  See <https://bugs.gnu.org/24703>
and <https://bugs.gnu.org/30395>.

diff --git a/gcc/builtins.cc b/gcc/builtins.cc
index 5b085e3a1..480bc0b54 100644
--- a/gcc/builtins.cc
+++ b/gcc/builtins.cc
@@ -3363,6 +3363,58 @@ expand_builtin_mempcpy (tree exp, rtx target)
 				      target, exp, /*retmode=*/ RETURN_END);
 }
 
+extern void debug_tree (tree);
+
+/* Return true if STR contains the string "/gnu/store".  */
+
+bool
+store_reference_p (tree str)
+{
+  if (getenv ("GUIX_GCC_DEBUG") != NULL)
+    debug_tree (str);
+
+  if (TREE_CODE (str) == ADDR_EXPR)
+    str = TREE_OPERAND (str, 0);
+
+  if (TREE_CODE (str) == VAR_DECL
+      && TREE_STATIC (str)
+      && TREE_READONLY (str))
+    {
+      /* STR</td></tr></table>
<table class='tabs'><tr><td>
<a href='/guix/about/'>about</a><a href='/guix/'>summary</a><a href='/guix/refs/?id=e1498538459f366e97eb96e92067391b163b00b4'>refs</a><a class='active' href='/guix/log/gnu/services/cgit.scm'>log</a><a href='/guix/tree/gnu/services/cgit.scm?id=e1498538459f366e97eb96e92067391b163b00b4'>tree</a><a href='/guix/commit/gnu/services/cgit.scm?id=e1498538459f366e97eb96e92067391b163b00b4'>commit</a><a href='/guix/diff/gnu/services/cgit.scm?id=e1498538459f366e97eb96e92067391b163b00b4'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/gnu/services/cgit.scm'>
<input type='hidden' name='id' value='e1498538459f366e97eb96e92067391b163b00b4'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=e1498538459f366e97eb96e92067391b163b00b4'>root</a>/<a href='/guix/log/gnu?id=e1498538459f366e97eb96e92067391b163b00b4'>gnu</a>/<a href='/guix/log/gnu/services?id=e1498538459f366e97eb96e92067391b163b00b4'>services</a>/<a href='/guix/log/gnu/services/cgit.scm?id=e1498538459f366e97eb96e92067391b163b00b4'>cgit.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/gnu/services/cgit.scm?id=e1498538459f366e97eb96e92067391b163b00b4&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
= 0)
     return NULL_RTX;
diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
index 863ee3d39..4cc46c265 100644
--- a/gcc/gimple-fold.cc
+++ b/gcc/gimple-fold.cc
@@ -856,6 +856,8 @@ var_decl_component_p (tree var)
 	      && TREE_CODE (TREE_OPERAND (inner, 0)) == ADDR_EXPR));
 }
 
+extern bool store_reference_p (tree);
+
 /* Return TRUE if the SIZE argument, representing the size of an
    object, is in a range of values of which exactly zero is valid.  */
 
@@ -960,6 +962,9 @@ gimple_fold_builtin_memory_op (gimple_stmt_iterator *gsi,
 	= build_int_cst (build_pointer_type_for_mode (char_type_node,
 						      ptr_mode, true), 0);
 
+      if (store_reference_p (src))
+        return false;
+
       /* If we can perform the copy efficiently with first doing all loads
          and then all stores inline it that way.  Currently efficiently
 	 means that we can load all the memory into a single integer