Refactor new b_hash(); better hash table clear (re: d8428a83)

The b_hash() function duplicated much of its code from b_alias(),
while b_alias() retained some code to support being called as
'hash'. There is no reason why 'hash' and 'alias' can't be handled
with a single function, as is the case several other builtins. Note
that option parsing can easily be made dependent on the name the
command was invoked with (in this case, argv[0]=='h').

The new hash builtin's -r option cleared the hash table by
assigning to PATH its existing value, triggering its associated
discipline function (put_restricted() in init.c) which then
actually cleared the hash table. That's a bit of a hack. It's nicer
if we can just do that directly. This requires taking a static
handler function rehash() from init.c, which invalidates one hash
table entry, and making it available to the builtin.

src/cmd/ksh93/bltins/typeset.c,
src/cmd/ksh93/include/builtins.h,
src/cmd/ksh93/include/nval.h,
src/cmd/ksh93/sh/init.c,
src/cmd/ksh93/sh/name.c:
- Merge b_hash() into b_alias().
- The -x option was still uselessly setting the NV_EXPORT flag.
  Exported aliases were in ksh88 but were removed in ksh93.
- Rename rehash() handler function from init.c to nv_rehash
  (avoiding a possible conflict with another rehash() in cd_pwd.c)
  and move it to name.c just above nv_scan(), which it's meant to
  be used with. Make it an extern so typeset.c can use it.
- b_alias(): Replace the PATH assignment by an nv_scan() call to
  clear the hash table directly using the nv_rehash() handler.

src/cmd/ksh93/data/builtins.c:
- POSIX compliance fix: Remove BLT_SPC (special builtin) flag from
  "alias" definition. 'alias' is specified as a regular builtin.
- sh_optalias[]: Fix uninformative -t option documentation.
- sh_opthash[]: Edit for conciseness and clarity.

src/cmd/ksh93/sh.1:
- Edit the 'alias -t' and 'hash' documentation.
- Remove the -- prefix from the 'alias' entry, which indicated that
  it was supposed to be a declaration builtin like 'typeset', with
  assignment-arguments expanding tildes and not being subject to
  field splitting. However, my testing shows that 'alias' has never
  actually behaved that way on ksh93. Even adding the BLT_DCL flag
  in data/builtins.c doesn't seem to change that.

(cherry picked from commit afa68dca5c786daa13213973e8b0f9bf3a1dadf6)

src/cmd/ksh93/bltins/typeset.c

@@ -133,56 +133,20 @@ int    b_readonly(int argc,char *argv[],Shbltin_t *context)
 	return(setall(argv,flag,tdata.sh->var_tree, &tdata));
 }
 
-int    b_hash(int argc,char *argv[],Shbltin_t *context)
+/*
-{
+ * 'alias' and 'hash' builtins
-	register unsigned flag = NV_NOARRAY | NV_NOSCOPE | NV_ASSIGN | NV_TAGGED;
+ */
-	register Dt_t *troot;
+#if 0
-	register int rflag=0, n;
+    /* for the dictionary generator */
-	struct tdata tdata;
+    int    b_hash(int argc,register char *argv[],Shbltin_t *context){}
-	NOT_USED(argc);
+#endif
-	memset((void *)&tdata, 0, sizeof(tdata));
-	tdata.sh = context->shp;
-	troot = tdata.sh->alias_tree;
-
-	/* The hash utility should not be recognized as the alias builtin */
-	tdata.aflag = '-';
-
-	while((n = optget(argv,sh_opthash))) switch(n)
-	{
-		case 'r':
-			rflag = 1;
-			break;
-		case ':':
-			error(2,"%s",opt_info.arg);
-			break;
-		case '?':
-			error(ERROR_usage(0),"%s",opt_info.arg);
-			return 2;
-	}
-	if (error_info.errors)
-		errormsg(SH_DICT,ERROR_usage(2),"%s",optusage(NULL));
-	argv += (opt_info.index-1);
-
-	/* Handle -r */
-	if (rflag)
-	{
-		Namval_t *np = nv_search((char *)PATHNOD, tdata.sh->var_tree, HASH_BUCKET);
-		nv_putval(np, nv_getval(np), NV_RDONLY);
-	}
-
-	troot = tdata.sh->track_tree;
-	/* We must fork in subshells to avoid polluting the parent shell's hash table. */
-	if(tdata.sh->subshell && !tdata.sh->subshare)
-		sh_subfork();
-	return setall(argv, flag, troot, &tdata);
-}
-
 int    b_alias(int argc,register char *argv[],Shbltin_t *context)
 {
 	register unsigned flag = NV_NOARRAY|NV_NOSCOPE|NV_ASSIGN;
 	register Dt_t *troot;
-	register int n;
+	register int rflag=0, n;
 	struct tdata tdata;
+	Namval_t *np;
 	NOT_USED(argc);
 	memset((void*)&tdata,0,sizeof(tdata));
 	tdata.sh = context->shp;
@@ -196,7 +160,7 @@ int    b_alias(int argc,register char *argv[],Shbltin_t *context)
 		*opt_info.option = 0;
 		tdata.argnum = 0;
 		tdata.aflag = *argv[1];
-		while((n = optget(argv,sh_optalias))) switch(n)
+		while((n = optget(argv, *argv[0]=='h' ? sh_opthash : sh_optalias))) switch(n)
 		{
 		    case 'p':
 			tdata.prefix = argv[0];
@@ -205,7 +169,10 @@ int    b_alias(int argc,register char *argv[],Shbltin_t *context)
 			flag |= NV_TAGGED;
 			break;
 		    case 'x':
-			flag |= NV_EXPORT;
+			/* obsolete, ignored */
+			break;
+		    case 'r':
+			rflag=1;
 			break;
 		    case ':':
 			errormsg(SH_DICT,2, "%s", opt_info.arg);
@@ -217,11 +184,18 @@ int    b_alias(int argc,register char *argv[],Shbltin_t *context)
 		if(error_info.errors)
 			errormsg(SH_DICT,ERROR_usage(2),"%s",optusage(NIL(char*)));
 		argv += (opt_info.index-1);
-		if(flag&NV_TAGGED)
-			troot = tdata.sh->track_tree;
 	}
-	if(context->shp->subshell && !context->shp->subshare)
+	/* fork a virtual subshell to avoid affecting parent shell's hash/alias table */
+	if((argv[1] || rflag) && tdata.sh->subshell && !tdata.sh->subshare)
 		sh_subfork();
+	/* 'alias -t', 'hash' */
+	if(flag&NV_TAGGED)
+	{
+		troot = tdata.sh->track_tree;	/* use hash table */
+		tdata.aflag = '-';		/* make setall() treat 'hash' like 'alias -t' */
+		if(rflag)			/* hash -r: clear hash table */
+			nv_scan(troot,nv_rehash,(void*)0,NV_TAGGED,NV_TAGGED);
+	}
 	return(setall(argv,flag,troot,&tdata));
 }
 

src/cmd/ksh93/data/builtins.c

@@ -78,8 +78,8 @@ const struct shtable3 shtab_builtins[] =
 #if _bin_newgrp || _usr_bin_newgrp
 	"newgrp",	NV_BLTIN|BLT_ENV|BLT_SPC,	Bltin(login),
 #endif	/* _bin_newgrp || _usr_bin_newgrp */
-	"alias",	NV_BLTIN|BLT_SPC,		bltin(alias),
+	"alias",	NV_BLTIN,			bltin(alias),
-	"hash",		NV_BLTIN,			bltin(hash),
+	"hash",		NV_BLTIN,			bltin(alias),
 	"enum",		NV_BLTIN|BLT_ENV|BLT_SPC|BLT_DCL,bltin(enum),
 	"eval",		NV_BLTIN|BLT_ENV|BLT_SPC|BLT_EXIT,bltin(eval),
 	"exit",		NV_BLTIN|BLT_ENV|BLT_SPC,	bltin(return),
@@ -339,7 +339,7 @@ USAGE_LICENSE
 
 const char sh_optalarm[]	= "r [varname seconds]";
 const char sh_optalias[] =
-"[-1c?\n@(#)$Id: alias (AT&T Research) 1999-07-07 $\n]"
+"[-1c?\n@(#)$Id: alias (AT&T Research/ksh community) 2020-06-10 $\n]"
 USAGE_LICENSE
 "[+NAME?alias - define or display aliases]"
 "[+DESCRIPTION?\balias\b creates or redefines alias definitions "
@@ -363,10 +363,9 @@ USAGE_LICENSE
 	"environment.  It does not effect scripts run by this shell.]"
 "[p?Causes the output to be in the form of alias commands that can be used "
 	"as input to the shell to recreate the current aliases.]"
-"[t?Used for tracked aliases.  These are aliases that connect a "
+"[t?Each \aname\a is looked up as a command in \b$PATH\b and its path is "
-	"command name to the pathname of the command and are reset "
+	"added to the hash table as a 'tracked alias'. If no \aname\a is "
-	"when the \bPATH\b variable is unset.  The tracked aliases feature is "
+	"given, this prints the hash table. See \bhash(1)\b.]"
-	"now obsolete.]"
 "[x?Ignored, this option is obsolete.]"
 "\n"
 "\n[name[=value]...]\n"
@@ -932,13 +931,12 @@ _JOB_
 const char sh_opthash[] =
 "[-1c?\n@(#)$Id: hash (ksh community) 2020-06-10 $\n]"
 "[+NAME?hash - display the locations of recently used programs]"
-"[+DESCRIPTION?The \bhash\b utility is used to display or modify "
+"[+DESCRIPTION?\bhash\b displays or modifies the hash table with the "
-	"the hash table, which contains the locations of "
+	"locations of recently used programs. If given no arguments, it lists "
-	"recently used programs.  When \bhash\b is given no arguments, "
+	"all command/path associations (a.k.a. 'tracked aliases') in the hash "
-	"it will list all commands in the hash table. If \autility\a is "
+	"table. Otherwise, \bhash\b performs a \bPATH\b search for each "
-     "supplied, \bhash\b will add that utility to the hash table.]"
+	"\autility\a supplied and adds the result to the hash table.]"
-"[r?This option will empty the hash table.  The effect of "
+"[r?Empty the hash table. This can also be achieved by resetting \bPATH\b.]"
-	"this flag can also be achieved by resetting the value of \bPATH\b.]"
 "\n"
 "\n[utility...]\n"
 "\n"
@@ -946,7 +944,6 @@ const char sh_opthash[] =
 	"[+0?Successful completion.]"
 	"[+>0?An error occured.]"
 "}"
-
 "[+SEE ALSO?\bsh\b(1), \balias\b(1)]"
 ;
 

src/cmd/ksh93/include/builtins.h

@@ -85,7 +85,6 @@ extern int b_builtin(int, char*[],Shbltin_t*);
 extern int b_cd(int, char*[],Shbltin_t*);
 extern int b_command(int, char*[],Shbltin_t*);
 extern int b_getopts(int, char*[],Shbltin_t*);
-extern int b_hash(int, char*[],Shbltin_t*);
 extern int b_hist(int, char*[],Shbltin_t*);
 extern int b_let(int, char*[],Shbltin_t*);
 extern int b_read(int, char*[],Shbltin_t*);

src/cmd/ksh93/include/nval.h

@@ -281,6 +281,7 @@ extern Namval_t		*nv_open(const char*,Dt_t*,int);
 extern void 		nv_putval(Namval_t*,const char*,int);
 extern void 		nv_putv(Namval_t*,const char*,int,Namfun_t*);
 extern int		nv_rename(Namval_t*,int);
+extern void		nv_rehash(Namval_t*,void*);
 extern int		nv_scan(Dt_t*,void(*)(Namval_t*,void*),void*,int,int);
 extern char 		*nv_setdisc(Namval_t*,const char*,Namval_t*,Namfun_t*);
 extern void		nv_setref(Namval_t*, Dt_t*,int);

src/cmd/ksh93/include/version.h

@@ -17,4 +17,4 @@
 *                  David Korn <dgk@research.att.com>                   *
 *                                                                      *
 ***********************************************************************/
-#define SH_RELEASE	"93u+m 2020-06-08"
+#define SH_RELEASE	"93u+m 2020-06-10"

src/cmd/ksh93/sh.1

@@ -5555,7 +5555,7 @@ command and the original positional parameters are restored upon completion.
 Otherwise the positional parameters are unchanged.
 The exit status is the exit status of the last command executed.
 .TP
-\(dg\(dg \f3alias\fP \*(OK \f3\-ptx\fP \*(CK  \*(OK \f2name\fP\*(OK \f3=\fP\f2value\^\fP  \*(CK \*(CK .\|.\|.
+\f3alias\fP \*(OK \f3\-ptx\fP \*(CK  \*(OK \f2name\fP\*(OK \f3=\fP\f2value\^\fP  \*(CK \*(CK .\|.\|.
 .B alias\^
 with no arguments prints the list of aliases
 in the form
@@ -5580,16 +5580,13 @@ A trailing space in
 .I value\^
 causes the next word to be checked for
 alias substitution.
-The obsolete
+With the
 .B \-t
-option is used to set and list tracked aliases.
+option, each name is looked up as a command in
-The value of a tracked alias is the full pathname
+.B $PATH
-corresponding to the given
+and its path is added to the hash table as a 'tracked alias'.
-.IR name .
+If no name is given, this prints the hash table. See
-The value becomes undefined when the value of
+.BR hash.
-.SM
-.B PATH
-is reset but the alias remains tracked.
 Without the
 .B \-t
 option,
@@ -6125,19 +6122,20 @@ The option
 can only be specified as the first option.
 .TP
 \f3hash\fP \*(OK \f3\-r\fP \f2\^\fP\*(CK \*(OK \f3utility\^\fP \*(CK
-The
+.B hash
-.BR hash
+displays or modifies the hash table with the locations of recently used
-command can be used to display or modify the hash table.
+programs. If given no arguments, it lists all command/path associations
-The hash table is a list of the most recently used programs
+(a.k.a. 'tracked aliases') in the hash table. Otherwise,
-and their locations.
+.B hash
-If
+performs a
+.B PATH
+search for each
 .I utility\^
-is supplied,
+supplied and adds the result to the hash table.
-.BR hash
+The
-will add that utility to the hash table.
-If
 .B \-r
-is selected, the hash table is reset.
+option empties the hash table. This can also be achieved by resetting
+.BR PATH.
 .TP
 .PD 0
 \f3hist\fP \*(OK \f3\-e\fP \f2ename\^\fP \ \*(CK \*(OK \f3\-nlr\^\fP \*(CK \*(OK \f2first\^\fP \*(OK \f2last\^\fP \*(CK \*(CK

src/cmd/ksh93/sh/init.c

@@ -229,15 +229,6 @@ static int		shlvl;
 static int		rand_shift;
 
 
-/*
- * Invalidate all path name bindings
- */
-static void rehash(register Namval_t *np,void *data)
-{
-	NOT_USED(data);
-	nv_onattr(np,NV_NOALIAS);
-}
-
 /*
  * out of memory routine for stak routines
  */
@@ -337,7 +328,8 @@ static void put_restricted(register Namval_t* np,const char *val,int flags,Namfu
 		errormsg(SH_DICT,ERROR_exit(1),e_restricted,nv_name(np));
 	if(np==PATHNOD	|| (path_scoped=(strcmp(name,PATHNOD->nvname)==0)))		
 	{
-		nv_scan(shp->track_tree,rehash,(void*)0,NV_TAGGED,NV_TAGGED);
+		/* Clear the hash table */
+		nv_scan(shp->track_tree,nv_rehash,(void*)0,NV_TAGGED,NV_TAGGED);
 		if(path_scoped && !val)
 			val = PATHNOD->nvalue.cp;
 	}

src/cmd/ksh93/sh/name.c

@@ -2317,6 +2317,15 @@ static int scanfilter(Dt_t *dict, void *arg, void *data)
 	return(0);
 }
 
+/*
+ * Handler function to invalidate a path name binding in the hash table
+ */
+void nv_rehash(register Namval_t *np,void *data)
+{
+	NOT_USED(data);
+	nv_onattr(np,NV_NOALIAS);
+}
+
 /*
  * Walk through the name-value pairs
  * if <mask> is non-zero, then only nodes with (nvflags&mask)==flags