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.

3 files changed, 14 insertions, 2 deletions

diff --git a/ChangeLog b/ChangeLog
index a7f78f3d9..668e303e4 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,12 @@
 2007-07-13  Jim Meyering  <jim@meyering.net>
 
+	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.
+
 	Use proper backslash-quoting inside backticks.
 	* configure.ac: Otherwise we run afoul of strict GNU tr:
 	a string ending in a lone backslash would provoke a failure.
diff --git a/NEWS b/NEWS
index 25fa3e98e..dc60e884f 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 28eeac35a..871542a27 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 = '\\';