From 96e2fde3ac9533fd7a40ccb8ad8a0737e00c1a5e Mon Sep 17 00:00:00 2001
From: Koichi Murase <myoga.murase@gmail.com>
Date: Tue, 5 Oct 2021 19:12:52 +0900
Subject: [PATCH] arrayfunc.c (unset_array_element): fix a bug that the first
 character of array subscript is skipped

---
 arrayfunc.c |  4 ++--
 subst.c     | 24 +++++++++++++++---------
 2 files changed, 17 insertions(+), 11 deletions(-)

diff --git a/arrayfunc.c b/arrayfunc.c
index 618f7c69..b75cc0b8 100644
--- a/arrayfunc.c
+++ b/arrayfunc.c
@@ -1074,7 +1074,7 @@ unbind_array_element (var, sub, flags)
   if (var && assoc_p (var) && (flags&VA_ONEWORD))
     len = strlen (sub) - 1;
   else
-    len = skipsubscript (sub, 0, flags&VA_NOEXPAND);	/* XXX */
+    len = skipsubscript (sub, 0, flags&VA_NOEXPAND | 2);	/* XXX */
   if (sub[len] != ']' || len == 0)
     {
       builtin_error ("%s[%s: %s", var->name, sub, _(bash_badsub_errmsg));
@@ -1330,7 +1330,7 @@ array_variable_name (s, flags, subp, lenp)
       return ((char *)NULL);
     }
   ind = t - s;
-  ni = skipsubscript (s, ind, flags);	/* XXX - was 0 not flags */
+  ni = skipsubscript (s, ind, flags & 1);	/* XXX - was 0 not flags */
   if (ni <= ind + 1 || s[ni] != ']')
     {
       err_badarraysub (s);
diff --git a/subst.c b/subst.c
index b4c84c62..5c7cbae9 100644
--- a/subst.c
+++ b/subst.c
@@ -1737,12 +1737,14 @@ unquote_bang (string)
 
 #define CQ_RETURN(x) do { no_longjmp_on_fatal_error = oldjmp; return (x); } while (0)
 
-/* This function assumes s[i] == open; returns with s[ret] == close; used to
-   parse array subscripts.  FLAGS & 1 means to not attempt to skip over
-   matched pairs of quotes or backquotes, or skip word expansions; it is
-   intended to be used after expansion has been performed and during final
-   assignment parsing (see arrayfunc.c:assign_compound_array_list()) or
-   during execution by a builtin which has already undergone word expansion. */
+/* This function assumes STRING[START] == OPEN (when (FLAGS & 2) == 0); returns
+   with STRING[ret] == CLOSE; used to parse array subscripts.  FLAGS & 1 means
+   to not attempt to skip over matched pairs of quotes or backquotes, or skip
+   word expansions; it is intended to be used after expansion has been
+   performed and during final assignment parsing (see
+   arrayfunc.c:assign_compound_array_list()) or during execution by a builtin
+   which has already undergone word expansion.  FLAGS & 2 means that
+   STRING[START] is the character just after the beginning OPEN. */
 static int
 skip_matched_pair (string, start, open, close, flags)
      const char *string;
@@ -1757,7 +1759,9 @@ skip_matched_pair (string, start, open, close, flags)
   oldjmp = no_longjmp_on_fatal_error;
   no_longjmp_on_fatal_error = 1;
 
-  i = start + 1;		/* skip over leading bracket */
+  i = start;
+  if ((flags & 2) == 0)
+    i++;		/* skip over leading bracket */
   count = 1;
   pass_next = backq = 0;
   ss = (char *)string;
@@ -1839,8 +1843,10 @@ skip_matched_pair (string, start, open, close, flags)
 
 #if defined (ARRAY_VARS)
 /* Flags has 1 as a reserved value, since skip_matched_pair uses it for
-   skipping over quoted strings and taking the first instance of the
-   closing character. */
+   skipping over quoted strings and taking the first instance of the closing
+   character.  When FLAGS has a bit 2, STRING[START] is assumed to be the
+   character after the opening `['.  Otherwise, STRING[START] contains the
+   opening `['. */
 int
 skipsubscript (string, start, flags)
      const char *string;
-- 
2.21.3