From d91c473c7c187079a886fcbc27fc7955da52a8fd Mon Sep 17 00:00:00 2001
From: ozan yigit <ozan.yigit@gmail.com>
Date: Tue, 23 Nov 2021 16:09:51 -0500
Subject: [PATCH] resolve parsing of a slash character within a cclass "/[/]/"
 without escape

---
 lex.c          | 33 +++++++++++++++++++++++++++++++--
 testdir/T.misc |  4 ----
 2 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/lex.c b/lex.c
index 9d1ae06..f588602 100644
--- a/lex.c
+++ b/lex.c
@@ -523,11 +523,12 @@ int regexpr(void)
 	static char *buf = NULL;
 	static int bufsz = 500;
 	char *bp;
+	int brackets = 0;
 
 	if (buf == NULL && (buf = (char *) malloc(bufsz)) == NULL)
-		FATAL("out of space for rex expr");
+		FATAL("out of space for reg expr");
 	bp = buf;
-	for ( ; (c = input()) != '/' && c != 0; ) {
+	for ( ; ((c = input()) != '/' || brackets > 0) && c != 0; ) {
 		if (!adjbuf(&buf, &bufsz, bp-buf+3, 500, &bp, "regexpr"))
 			FATAL("out of space for reg expr %.10s...", buf);
 		if (c == '\n') {
@@ -538,6 +539,34 @@ int regexpr(void)
 		} else if (c == '\\') {
 			*bp++ = '\\';
 			*bp++ = input();
+		} else if (c == '[') {
+			*bp++ = c;
+			brackets++;
+			if ((c = input()) == '^') {
+				*bp++ = c;
+				if ((c = input()) == ']') {
+					*bp++ = c;
+					if ((c = input()) == '[')
+						*bp++ = c;
+					else
+						unput(c);
+				} else if (c == '[') {
+					*bp++ = c;
+				} else
+					unput(c);
+			} else if (c == ']') {	/* []] is ok */
+				*bp++ = c;
+				if ((c = input()) == '[')
+					*bp++ = c;
+				else
+					unput(c);
+			} else if (brackets == 1 && c == '[') {	/* [[] is also ok */
+				*bp++ = c;
+			} else
+				unput(c);
+		} else if (c == ']') {
+			*bp++ = c;
+			brackets--;
 		} else {
 			*bp++ = c;
 		}
diff --git a/testdir/T.misc b/testdir/T.misc
index ad34ab8..f12d459 100755
--- a/testdir/T.misc
+++ b/testdir/T.misc
@@ -164,10 +164,6 @@ $awk 'BEGIN { unireghf() }
 function unireghf(hfeed) { hfeed[1] = 0 }'
 if test -r core; then echo 1>&2 "BAD: T.misc unireghf dropped core"; fi
 
-echo x | $awk '/[/]/' 2>foo
-grep 'nonterminated character class' foo >/dev/null || error 'BAD: T.misc nonterminated fails'
-if test -r core; then echo 1>&2 "BAD: T.misc nonterminated dropped core"; fi
-
 $awk '
 function f() { return 12345 }
 BEGIN { printf "<%s>\n", f() }