Fix "$*" doing pattern matching if $IFS is wildcard (BUG_IFSGLOBS)

The bug is that "$*", and related expansions such as "${arr[*]}",
etc., do pattern matching if the first character of $IFS is a
wildcard. For example, the following:

    IFS=*
    set -- F ''
    case BUGFREE in
    BUG"$*")        echo bug ;;
    esac

outputs 'bug'. This bug can be reproduced in every other glob
pattern matching context as well, but not in pathname expansion.

src/cmd/ksh93/sh/macro.c: varsub():
- When joining fields into one for a "$*"-type expansion, check if
  a glob pattern matching operation follows (mp->pattern is set).
  If so, write a preceding backslash to escape the separator.

Resolves: https://github.com/ksh93/ksh/issues/489
Resolves: https://github.com/att/ast/issues/12

NEWS

@@ -3,6 +3,11 @@ For full details, see the git log at: https://github.com/ksh93/ksh/tree/1.0
 
 Any uppercase BUG_* names are modernish shell bug IDs.
 
+2022-07-28:
+
+- Fixed BUG_IFSGLOBS ("$*" does pattern matching if the first character of
+  $IFS is a wildcard).
+
 2022-07-27:
 
 - Fixed a bug introduced on 2022-02-08 where $PPID was incorrect when a script

src/cmd/ksh93/include/version.h

@@ -17,8 +17,8 @@
 #include <releaseflags.h>
 
 #define SH_RELEASE_FORK	"93u+m"		/* only change if you develop a new ksh93 fork */
-#define SH_RELEASE_SVER	"1.0.0-rc.3"	/* semantic version number: https://semver.org */
-#define SH_RELEASE_DATE	"2022-07-27"	/* must be in this format for $((.sh.version)) */
+#define SH_RELEASE_SVER	"1.0.0-rc.4"	/* semantic version number: https://semver.org */
+#define SH_RELEASE_DATE	"2022-07-28"	/* must be in this format for $((.sh.version)) */
 #define SH_RELEASE_CPYR	"(c) 2020-2022 Contributors to ksh " SH_RELEASE_FORK
 
 /* Scripts sometimes field-split ${.sh.version}, so don't change amount of whitespace. */

src/cmd/ksh93/sh/macro.c

@@ -59,7 +59,7 @@ typedef struct  _mac_
 	char		quote;		/* set within double quoted contexts */
 	char		lit;		/* set within single quotes */
 	char		split;		/* set when word splitting is possible */
-	char		pattern;	/* set when file expansion follows */
+	char		pattern;	/* set when glob pattern expansion or matching follows */
 	char		patfound;	/* set if pattern character found */
 	char		assign;		/* set for assignments */
 	char		arith;		/* set for ((...)) */
@@ -1985,6 +1985,8 @@ retry2:
 				 * We're joining fields into one; write the output field separator, which may be multi-byte.
 				 * For "$@" it's a space, for "$*" it's the 1st char of IFS (space if unset, none if empty).
 				 */
+				if(mp->pattern)				/* avoid BUG_IFSGLOBS */
+					sfputc(sfio_ptr, '\\');
 				if(mode == '@' || !mp->ifsp)		/* if expanding $@ or if IFS is unset... */
 					sfputc(sfio_ptr, ' ');
 				else if(mp->ifs)			/* else if IFS is non-empty... */

src/cmd/ksh93/tests/quoting2.sh

@@ -313,5 +313,44 @@ three
 [[ $got == "$exp" ]] || err_exit "Line continuation broken within backtick command substitution" \
 	"(expected $(printf %q "$exp"), got $(printf %q "$got"))"
 
+# ======
+# BUG_IFSGLOBS: https://github.com/ksh93/ksh/issues/489
+# "$*" does pattern matching if the first char of $IFS is a wildcard
+
+IFS=*			# output field separator for "$*"
+set -- F ''		# "$*" is now "F*"
+exp=BUGFREE
+got=${exp%"$*"}		# the quoted "*" in "F*" should not act as a wildcard
+[[ $got == "$exp" ]] || err_exit 'BUG_IGSGLOBS reproducer 1' \
+	"(expected $(printf %q "$exp"), got $(printf %q "$got"))"
+case BUGFREE in
+BUG"$*")	err_exit 'BUG_IFSGLOBS reproducer 2' ;;
+BUGFREE)	;;
+*)		err_exit 'BUG_IFSGLOBS reproducer 2 fails badly' ;;
+esac
+
+IFS=?
+exp=abcd
+set a c
+got=${exp#"$*"}
+[[ $got == "$exp" ]] || err_exit 'BUG_IFSGLOBS reproducer 3' \
+	"(expected $(printf %q "$exp"), got $(printf %q "$got"))"
+case abc in
+"$*")	err_exit 'BUG_IFSGLOBS reproducer 4' ;;
+esac
+[[ abc = "$*" ]] && err_exit 'BUG_IFSGLOBS reproducer 5'
+
+# https://unix.stackexchange.com/questions/411001/using-case-and-arrays-together-in-bash/411006#411006
+IFS='|'
+arr=(opt1 opt2 opt3)
+case opt2 in
+@("${arr[*]}"))
+	err_exit 'BUG_IFSGLOBS reproducer 6' ;;
+esac
+[[ opt2 == @("${arr[*]}") ]] && err_exit 'BUG_IFSGLOBS reproducer 7'
+unset arr
+
+IFS=$' \t\n'
+
 # ======
 exit $((Errors<125?Errors:125))