From cfc37be4862574ac68f424a42763cf5681243812 Mon Sep 17 00:00:00 2001
From: "Roberto E. Vargas Caballero" <k0ga@shike2.com>
Date: Sat, 23 Jan 2016 09:11:33 +0100
Subject: [PATCH] Do not try to rematch patterns with ^ or $

It is impossible to rematch a pattern which has one (or both)
of these operators, so the simplest solucion is detect them
while we are compiling the regular expression and break the
match loop after the first iteration.
---
 ed.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/ed.c b/ed.c
index 4a872ed..ce19cf7 100644
--- a/ed.c
+++ b/ed.c
@@ -63,6 +63,7 @@ static char *rhs;
 static char *lastmatch;
 static struct undo udata;
 static int newcmd;
+int eol, bol;
 
 static void
 discard(void)
@@ -358,11 +359,15 @@ compile(int delim)
 	if (!isgraph(delim))
 		error("invalid pattern delimiter");
 
-	bracket = siz = 0;
+	eol = bol = bracket = siz = 0;
 	for (n = 0;; ++n) {
 		if ((c = input()) == delim && !bracket)
 			break;
-		if (c == '\n' || c == EOF) {
+		if (c == '^') {
+			bol = 1;
+		} else if (c == '$') {
+			eol = 1;
+		} else if (c == '\n' || c == EOF) {
 			back(c);
 			break;
 		}
@@ -1005,9 +1010,11 @@ subline(int num, int nth)
 	static size_t siz, cap;
 
 	i = changed = siz = 0;
-	for (m = match(num); m && *lastmatch != '\n'; m = rematch(num)) {
+	for (m = match(num); m; m = rematch(num)) {
 		addpre(&s, &cap, &siz);
 		changed |= addsub(&s, &cap, &siz, nth, ++i);
+		if (eol || bol)
+			break;
 	}
 	if (!changed)
 		return;