Fix typo in strncat, wcsncat manual entries

* manual/string.texi (Copying and Concatenation): Fix typos in
sample implementations of strncat and wcsncat, by having them use
the old value of the destination length, not the new one.

1 files changed, 6 insertions, 4 deletions

diff --git a/manual/string.texi b/manual/string.texi
index 4f276a95ae..8f0f5fa1d2 100644
--- a/manual/string.texi
+++ b/manual/string.texi
@@ -996,8 +996,9 @@ The @code{strncat} function could be implemented like this:
 char *
 strncat (char *to, const char *from, size_t size)
 @{
-  memcpy (to + strlen (to), from, strnlen (from, size));
-  to[strlen (to) + strnlen (from, size)] = '\0';
+  size_t len = strlen (to);
+  memcpy (to + len, from, strnlen (from, size));
+  to[len + strnlen (from, size)] = '\0';
   return to;
 @}
 @end group
@@ -1025,8 +1026,9 @@ wchar_t *
 wcsncat (wchar_t *restrict wto, const wchar_t *restrict wfrom,
          size_t size)
 @{
-  memcpy (wto + wcslen (wto), wfrom, wcsnlen (wfrom, size) * sizeof (wchar_t));
-  wto[wcslen (to) + wcsnlen (wfrom, size)] = '\0';
+  size_t len = wcslen (wto);
+  memcpy (wto + len, wfrom, wcsnlen (wfrom, size) * sizeof (wchar_t));
+  wto[len + wcsnlen (wfrom, size)] = L'\0';
   return wto;
 @}
 @end group