[PATCH] \N'nnn' protection.

[Kristaps Dzonsons <kristaps@bsd.lv>]

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Hi,

Enclosed is a patch to limit possible \N'nnn' escapes.  \N transforms 
the number 'nnn' into its character representation and is marked as "for 
backwards compatibility" in mandoc_char(7).

I can only find manuals using this for the double-quote \N'34', so this 
seems safe, but maybe one of you knows of crazy \N usage that would 
inspire me to re-think.  However, throwing, e.g., the \b character in 
there will cause at least -Tps and -Tpdf to puke.

Thoughts?

Kristaps

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Index: chars.c
===================================================================
RCS file: /usr/vhosts/mdocml.bsd.lv/cvs/mdocml/chars.c,v
retrieving revision 1.39
diff -u -r1.39 chars.c
--- chars.c	30 Apr 2011 22:24:31 -0000	1.39
+++ chars.c	30 Apr 2011 22:31:11 -0000
@@ -20,6 +20,7 @@
 #endif
 
 #include <assert.h>
+#include <ctype.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -148,12 +149,10 @@
 		return('\0');
 
 	i = atoi(p);
-	/* 
-	 * FIXME:
-	 * This is wrong.  Anything could be written here!
-	 * This should be carefully screened for possible characters.
-	 */
-	return(i <= 0 || i > 255 ? '\0' : (char)i);
+	if (isalnum(i) || ispunct(i) || ' ' == (char)i)
+		return(i);
+
+	return('\0');
 }