From: Mohamed Akram <mohd.akram@outlook.com>
Subject: Re: sed: check length before append in substitute
To: "tech@openbsd.org" <tech@openbsd.org>
Date: Sat, 24 Aug 2024 09:02:18 +0000

Thoughts on this patch?

> On Aug 16, 2024, at 6:33 PM, Mohamed Akram <mohd.akram@live.com> wrote:
> 
> This resolves the case where the pattern space is empty but does not
> start with a null character, which might occur after using the D
> command. This can be seen in the following sed program, which should
> print its input as-is:
> 
> 	printf 'foo\n\n' | sed -e 's/^//p' -e '$!N' -e D
> 
> --- src/usr.bin/sed/process.c.orig	2024-08-16 17:35:20
> +++ src/usr.bin/sed/process.c	2024-08-16 17:35:52
> @@ -387,14 +387,12 @@
> 		 * and at the end of the line, terminate.
> 		 */
> 		if (match[0].rm_so == match[0].rm_eo) {
> -			if (*s == '\0' || *s == '\n')
> -				slen = -1;
> -			else
> -				slen--;
> -			if (*s != '\0') {
> +			if (slen > 0) {
> 				cspace(&SS, s++, 1, APPEND);
> +				slen--;
> 				le++;
> -			}
> +			} else
> +				slen = -1;
> 			lastempty = 1;
> 		} else
> 			lastempty = 0;
>