From 9439ce094c9aa7557a9d53ac7b412a23aa66e36b Mon Sep 17 00:00:00 2001
From: Chet Ramey <chet.ramey@case.edu>
Date: Tue, 4 Jan 2022 17:03:45 -0500
Subject: [PATCH] Bash-5.1 patch 16: fix interpretation of multiple instances
 of ! in [[ conditional commands

---
 parse.y      | 2 +-
 patchlevel.h | 2 +-
 y.tab.c      | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/parse.y b/parse.y
index f25575b5..f4168c7c 100644
--- a/parse.y
+++ b/parse.y
@@ -4796,7 +4796,7 @@ cond_term ()
 	dispose_word (yylval.word);	/* not needed */
       term = cond_term ();
       if (term)
-	term->flags |= CMD_INVERT_RETURN;
+	term->flags ^= CMD_INVERT_RETURN;
     }
   else if (tok == WORD && yylval.word->word[0] == '-' && yylval.word->word[1] && yylval.word->word[2] == 0 && test_unop (yylval.word->word))
     {
diff --git a/patchlevel.h b/patchlevel.h
index 252e0819..3c226949 100644
--- a/patchlevel.h
+++ b/patchlevel.h
@@ -25,6 +25,6 @@
    regexp `^#define[ 	]*PATCHLEVEL', since that's what support/mkversion.sh
    looks for to find the patch level (for the sccs version string). */
 
-#define PATCHLEVEL 15
+#define PATCHLEVEL 16
 
 #endif /* _PATCHLEVEL_H_ */
diff --git a/y.tab.c b/y.tab.c
index c11d7aaa..78b38250 100644
--- a/y.tab.c
+++ b/y.tab.c
@@ -7090,7 +7090,7 @@ cond_term ()
 	dispose_word (yylval.word);	/* not needed */
       term = cond_term ();
       if (term)
-	term->flags |= CMD_INVERT_RETURN;
+	term->flags ^= CMD_INVERT_RETURN;
     }
   else if (tok == WORD && yylval.word->word[0] == '-' && yylval.word->word[1] && yylval.word->word[2] == 0 && test_unop (yylval.word->word))
     {
-- 
2.31.1