Avoid printing a [0] element for ${!.sh.match} (#709)

This fix prevents name_match() in init.c from printing a
spurious extra subscript when using ${!.sh.match}.

src/cmd/ksh93/sh/init.c:
- Remove the name_match() function and roll SH_MATCH_disc
  back to the 93u+ version.

Resolves: #308

NEWS

@@ -7,6 +7,9 @@ Uppercase BUG_* IDs are shell bug IDs as used by the Modernish shell library.
 - Fixed a rare crash or rare incorrect behaviour in .sh.tilde.{get,set}
   discipline functions for ~ expansion (see 2021-03-16 below).
 
+- Fixed a bug that caused listing the .sh.match variable with ${!.sh.match} to
+  show spurious elements.
+
 2024-01-22:
 
 - Fixed a bug in the loop invariants optimizer (SHOPT_OPTIMIZE) that caused

src/cmd/ksh93/sh/init.c

@@ -1012,15 +1012,7 @@ static char* get_match(Namval_t* np, Namfun_t *fp)
 	return mp->rval[i];
 }
 
-static char *name_match(Namval_t *np, Namfun_t *fp)
-{
-	int sub = nv_aindex(SH_MATCHNOD);
-	sfprintf(sh.strbuf,".sh.match[%d]",sub);
-	return sfstruse(sh.strbuf);
-}
-
-static const Namdisc_t SH_MATCH_disc = { sizeof(struct match), 0, get_match,
-	0,0,0,0,name_match };
+static const Namdisc_t SH_MATCH_disc  = { sizeof(struct match), 0, get_match };
 
 static char* get_version(Namval_t* np, Namfun_t *fp)
 {

src/cmd/ksh93/tests/sh_match.sh

@@ -1072,5 +1072,13 @@ fi
 [[ "[a] b [c] d" =~ ^\[[^]]+\] ]]
 [[ ${.sh.match} == '[a]' ]] || err_exit 'pattern ^\[[^]]+ broken'
 
+# Avoid printing excessive elements for .sh.match
+# https://github.com/ksh93/ksh/issues/308#issuecomment-1033259414
+# https://github.com/ksh93/ksh/pull/709
+exp='.sh.match .sh.match[1] .sh.match[2]'
+got=${ $SHELL -c 'print ${!.sh.match} ${!.sh.match[1]} ${!.sh.match[2]}' }
+[[ $exp == "$got" ]] || err_exit "'print \${!.sh.match}' should not print excessive elements" \
+	"(expected ${ printf %q "$exp" }, got ${ printf %q "$got" })"
+
 # ======
 exit $((Errors<125?Errors:125))