Load 'r' and 'history' default aliases on interactive only

These two default aliases are useful on interactive shells. In
scripts, they interfere with possible function or command names.

As of this commit, these final two default aliases are only loaded
for interactive shells, leaving zero default aliases for scripts.
This completes the project to get rid of misguided default aliases.

src/cmd/ksh93/include/shtable.h,
src/cmd/ksh93/data/aliases.c:
src/cmd/ksh93/sh/init.c:
- Add empty alias table shtab_noaliases[] for scripts.
- Rename inittree() to sh_inittree() and make it external.
- nv_init(), sh_reinit(): Initialise empty alias tree for scripts.

src/cmd/ksh93/sh/main.c: sh_main():
- If interactive, reinitialise alias tree for interactive shells.

src/cmd/ksh93/tests/alias.sh:
- To test default alias removal, launch shell with -i.

NEWS

@@ -10,6 +10,9 @@ Any uppercase BUG_* names are modernish shell bug IDs.
   that 'unalias -a' does not remove them. Shell functions can now use
   these names, which improves compatibility with POSIX shell scripts.
 
+- The two default aliases that are left, 'history' and 'r', are now only
+  loaded on interactive shells, leaving zero default aliases for scripts.
+
 - The End key escape sequence '^[[F' is now handled in the emacs and vi editing
   modes. The End key moves the cursor to the end of the line (in contrast to
   the Home key doing the opposite).

TODO

@@ -14,27 +14,6 @@ Fix build system:
   to take effect. The machine-generated Mamfiles are now used as a fallback,
   but they are not meant to be edited by hand.
 
-______
-Fix or remove broken or misguided default aliases:
-
-- Make proper builtins out of the following scripting-related aliases, so
-  that 'unalias -a' does not eliminate them. If done correctly, this causes
-  no other change in behaviour. It would be good practice to 'unalias -a' in
-  a script to start with a clean slate, except ksh has always made that
-  impossible without losing these. Default aliases should be to facilitate
-  interactive use.
-	- autoload='typeset -fu'
-	- compound='typeset -C'
-	- float='typeset -lE'
-	- functions='typeset -f'
-	- integer='typeset -li'
-	- nameref='typeset -n'
-  Keep these default aliases for the benefit of interactive shells:
-	+ history='hist -l'
-	+ r='hist -s'
-  To avoid interfering with shell functions by those names that POSIX
-  scripts may set, those should only initialise on interactive shells.
-
 ______
 Fix currently known bugs affecting shell scripting. These are identified by
 their modernish IDs. For exact details, see code/comments in:

src/cmd/ksh93/data/aliases.c

@@ -24,7 +24,7 @@
 #include	"FEATURE/dynamic"
 
 /*
- * This is the table of built-in aliases.  These should be exported.
+ * Table of built-in aliases for interactive shells.
  */
 
 const struct shtable2 shtab_aliases[] =
@@ -34,3 +34,12 @@ const struct shtable2 shtab_aliases[] =
 	"",		0,			(char*)0
 };
 
+/*
+ * Empty table of built-in aliases for non-interactive shells.
+ */
+
+const struct shtable2 shtab_noaliases[] =
+{
+	"",		0,			(char*)0
+};
+

src/cmd/ksh93/include/shtable.h

@@ -56,10 +56,12 @@ extern const Shtable_t		shtab_options[];
 extern const Shtable_t		shtab_attributes[];
 extern const struct shtable2	shtab_variables[];
 extern const struct shtable2	shtab_aliases[];
+extern const struct shtable2	shtab_noaliases[];
 extern const struct shtable2	shtab_signals[];
 extern const struct shtable3	shtab_builtins[];
 extern const Shtable_t		shtab_reserved[];
 extern const Shtable_t		*sh_locate(const char*, const Shtable_t*, int);
 extern int			sh_lookopt(const char*, int*);
+extern Dt_t			*sh_inittree(Shell_t*, const struct shtable2*);
 
 #endif /* SH_TABLE_H */

src/cmd/ksh93/sh/init.c

@@ -217,7 +217,6 @@ static int		lctype;
 static int		nbltins;
 static void		env_init(Shell_t*);
 static Init_t		*nv_init(Shell_t*);
-static Dt_t		*inittree(Shell_t*,const struct shtable2*);
 static int		shlvl;
 
 #ifdef _WINIX
@@ -1561,7 +1560,7 @@ int sh_reinit(char *argv[])
 		nv_delete(np,dp,NV_NOFREE);
 	}
 	dtclose(shp->alias_tree);
-	shp->alias_tree = inittree(shp,shtab_aliases);
+	shp->alias_tree = sh_inittree(shp,shtab_noaliases);
 	shp->last_root = shp->var_tree;
 	shp->inuse_bits = 0;
 	if(shp->userinit)
@@ -1760,7 +1759,7 @@ static Init_t *nv_init(Shell_t *shp)
 	shp->nvfun.last = (char*)shp;
 	shp->nvfun.nofree = 1;
 	ip->sh = shp;
-	shp->var_base = shp->var_tree = inittree(shp,shtab_variables);
+	shp->var_base = shp->var_tree = sh_inittree(shp,shtab_variables);
 	SHLVL->nvalue.ip = &shlvl;
 	ip->IFS_init.hdr.disc = &IFS_disc;
 	ip->PATH_init.disc = &RESTRICTED_disc;
@@ -1853,9 +1852,9 @@ static Init_t *nv_init(Shell_t *shp)
 	(MCHKNOD)->nvalue.lp = (&sh_mailchk);
 	(OPTINDNOD)->nvalue.lp = (&shp->st.optindex);
 	/* set up the seconds clock */
-	shp->alias_tree = inittree(shp,shtab_aliases);
+	shp->alias_tree = sh_inittree(shp,shtab_noaliases);
 	shp->track_tree = dtopen(&_Nvdisc,Dtset);
-	shp->bltin_tree = inittree(shp,(const struct shtable2*)shtab_builtins);
+	shp->bltin_tree = sh_inittree(shp,(const struct shtable2*)shtab_builtins);
 	shp->fun_tree = dtopen(&_Nvdisc,Dtoset);
 	dtview(shp->fun_tree,shp->bltin_tree);
 	nv_mount(DOTSHNOD, "type", shp->typedict=dtopen(&_Nvdisc,Dtoset));
@@ -1878,7 +1877,7 @@ static Init_t *nv_init(Shell_t *shp)
  * initialize name-value pairs
  */
 
-static Dt_t *inittree(Shell_t *shp,const struct shtable2 *name_vals)
+Dt_t *sh_inittree(Shell_t *shp,const struct shtable2 *name_vals)
 {
 	register Namval_t *np;
 	register const struct shtable2 *tp;

src/cmd/ksh93/sh/main.c

@@ -176,6 +176,8 @@ int sh_main(int ac, char *av[], Shinit_f userinit)
 		{
 			sh_onoption(SH_BGNICE);
 			sh_onoption(SH_RC);
+			free(shp->alias_tree);
+			shp->alias_tree = sh_inittree(shp,shtab_aliases);
 		}
 		if(!sh_isoption(SH_RC) && (sh_isoption(SH_BASH) && !sh_isoption(SH_POSIX)
 #if SHOPT_REMOTE

src/cmd/ksh93/tests/alias.sh

@@ -110,7 +110,7 @@ unalias foo
 unalias foo && err_exit 'unalias should return non-zero when a previously set alias is unaliased twice'
 
 # Removing a predefined alias should work without an error from free(3)
-$SHELL -c 'unalias history' 2> /dev/null || err_exit 'removing a predefined alias does not work'
+$SHELL -i -c 'unalias history' 2> /dev/null || err_exit 'removing a predefined alias does not work'
 
 # ======
 exit $((Errors<125?Errors:125))