FYI: tr now warns about unescaped backslash at end of string

[Jim Meyering]

        Warn about non-portable use of unescaped backslash at end of string,
        and treat it as if it were escaped.
        * src/tr.c (unquote): Considering that such usage would make GNU tr
        from coreutils-5.2.1 and earlier *fail*, the least we can do now is
        to warn about it.  Solaris' tr ignores it.
        * NEWS: Mention this.

diff --git a/NEWS b/NEWS
index 25fa3e9..dc60e88 100644
--- a/NEWS
+++ b/NEWS
@@ -12,6 +12,10 @@ GNU coreutils NEWS                                    -*- 
outline -*-
   pr -F no longer suppresses the footer or the first two blank lines in
   the header.  This is for compatibility with BSD and POSIX.

+  tr now warns about an unescaped backslash at end of string.
+  The tr from coreutils-5.2.1 and earlier would fail for such usage,
+  and Solaris' tr ignores that final byte.
+
 ** New features

   Add SELinux support (FIXME: add details here)
diff --git a/src/tr.c b/src/tr.c
index 28eeac3..871542a 100644
--- a/src/tr.c
+++ b/src/tr.c
@@ -525,8 +525,9 @@ unquote (char const *s, struct E_string *es)
                }
              break;
            case '\0':
-             /* POSIX seems to require that a trailing backslash must
-                stand for itself.  Weird.  */
+             error (0, 0, _("warning: an unescaped backslash "
+                            "at end of string is not portable"));
+             /* POSIX is not clear about this.  */
              es->escaped[j] = false;
              i--;
              c = '\\';