+/* If we have mmap() and mprotect(), copy the string S just before a
+ protected page, so that if the demangler runs over the end of the
+ string we'll get a fault, and return the address of the new string.
+ If no mmap, or it fails, or it looks too hard, just return S. */
+
+#ifdef HAVE_SYS_MMAN_H
+#include <sys/mman.h>
+#endif
+#if defined(MAP_ANON) && ! defined (MAP_ANONYMOUS)
+#define MAP_ANONYMOUS MAP_ANON
+#endif
+
+static const char *
+protect_end (const char * s)
+{
+#if defined(HAVE_MMAP) && defined (MAP_ANONYMOUS)
+ size_t pagesize = getpagesize();
+ static char * buf;
+ size_t s_len = strlen (s);
+ char * result;
+
+ /* Don't try if S is too long. */
+ if (s_len >= pagesize)
+ return s;
+
+ /* Allocate one page of allocated space followed by an unmapped
+ page. */
+ if (buf == NULL)
+ {
+ buf = mmap (NULL, pagesize * 2, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+ if (! buf)
+ return s;
+ munmap (buf + pagesize, pagesize);
+ }
+
+ result = buf + (pagesize - s_len - 1);
+ memcpy (result, s, s_len + 1);
+ return result;
+#else
+ return s;
+#endif
+}
+