/* vi:set ts=8 sts=4 sw=4 noet:
 *
 * VIM - Vi IMproved	by Bram Moolenaar
 *
 * Do ":help uganda"  in Vim to read copying and usage conditions.
 * Do ":help credits" in Vim to see a list of people who contributed.
 * See README.txt for an overview of the Vim source code.
 */

/*
 * evalvars.c: functions for dealing with variables
 */

#include "vim.h"

#if defined(FEAT_EVAL) || defined(PROTO)

static dictitem_T	globvars_var;		// variable used for g:
static dict_T		globvardict;		// Dictionary with g: variables
#define globvarht globvardict.dv_hashtab

/*
 * Old Vim variables such as "v:version" are also available without the "v:".
 * Also in functions.  We need a special hashtable for them.
 */
static hashtab_T	compat_hashtab;

/*
 * Array to hold the value of v: variables.
 * The value is in a dictitem, so that it can also be used in the v: scope.
 * The reason to use this table anyway is for very quick access to the
 * variables with the VV_ defines.
 */

// values for vv_flags:
#define VV_COMPAT	1	// compatible, also used without "v:"
#define VV_RO		2	// read-only
#define VV_RO_SBX	4	// read-only in the sandbox

#define VV_NAME(s, t)	s, {{t, 0, {0}}, 0, {0}}

typedef struct vimvar vimvar_T;

static struct vimvar
{
    char	*vv_name;	// name of variable, without v:
    dictitem16_T vv_di;		// value and name for key (max 16 chars!)
    char	vv_flags;	// VV_COMPAT, VV_RO, VV_RO_SBX
} vimvars[VV_LEN] =
{
    // The order here must match the VV_ defines in vim.h!
    // Initializing a union does not work, leave tv.vval empty to get zero's.
    {VV_NAME("count",		 VAR_NUMBER), VV_COMPAT+VV_RO},
    {VV_NAME("count1",		 VAR_NUMBER), VV_RO},
    {VV_NAME("prevcount",	 VAR_NUMBER), VV_RO},
    {VV_NAME("errmsg",		 VAR_STRING), VV_COMPAT},
    {VV_NAME("warningmsg",	 VAR_STRING), 0},
    {VV_NAME("statusmsg",	 VAR_STRING), 0},
    {VV_NAME("shell_error",	 VAR_NUMBER), VV_COMPAT+VV_RO},
    {VV_NAME("this_session",	 VAR_STRING), VV_COMPAT},
    {VV_NAME("version",		 VAR_NUMBER), VV_COMPAT+VV_RO},
    {VV_NAME("lnum",		 VAR_NUMBER), VV_RO_SBX},
    {VV_NAME("termresponse",	 VAR_STRING), VV_RO},
    {VV_NAME("fname",		 VAR_STRING), VV_RO},
    {VV_NAME("lang",		 VAR_STRING), VV_RO},
    {VV_NAME("lc_time",		 VAR_STRING), VV_RO},
    {VV_NAME("ctype",		 VAR_STRING), VV_RO},
    {VV_NAME("charconvert_from", VAR_STRING), VV_RO},
    {VV_NAME("charconvert_to",	 VAR_STRING), VV_RO},
    {VV_NAME("fname_in",	 VAR_STRING), VV_RO},
    {VV_NAME("fname_out",	 VAR_STRING), VV_RO},
    {VV_NAME("fname_new",	 VAR_STRING), VV_RO},
    {VV_NAME("fname_diff",	 VAR_STRING), VV_RO},
    {VV_NAME("cmdarg",		 VAR_STRING), VV_RO},
    {VV_NAME("foldstart",	 VAR_NUMBER), VV_RO_SBX},
    {VV_NAME("foldend",		 VAR_NUMBER), VV_RO_SBX},
    {VV_NAME("folddashes",	 VAR_STRING), VV_RO_SBX},
    {VV_NAME("foldlevel",	 VAR_NUMBER), VV_RO_SBX},
    {VV_NAME("progname",	 VAR_STRING), VV_RO},
    {VV_NAME("servername",	 VAR_STRING), VV_RO},
    {VV_NAME("dying",		 VAR_NUMBER), VV_RO},
    {VV_NAME("exception",	 VAR_STRING), VV_RO},
    {VV_NAME("throwpoint",	 VAR_STRING), VV_RO},
    {VV_NAME("register",	 VAR_STRING), VV_RO},
    {VV_NAME("cmdbang",		 VAR_NUMBER), VV_RO},
    {VV_NAME("insertmode",	 VAR_STRING), VV_RO},
    {VV_NAME("val",		 VAR_UNKNOWN), VV_RO},
    {VV_NAME("key",		 VAR_UNKNOWN), VV_RO},
    {VV_NAME("profiling",	 VAR_NUMBER), VV_RO},
    {VV_NAME("fcs_reason",	 VAR_STRING), VV_RO},
    {VV_NAME("fcs_choice",	 VAR_STRING), 0},
    {VV_NAME("beval_bufnr",	 VAR_NUMBER), VV_RO},
    {VV_NAME("beval_winnr",	 VAR_NUMBER), VV_RO},
    {VV_NAME("beval_winid",	 VAR_NUMBER), VV_RO},
    {VV_NAME("beval_lnum",	 VAR_NUMBER), VV_RO},
    {VV_NAME("beval_col",	 VAR_NUMBER), VV_RO},
    {VV_NAME("beval_text",	 VAR_STRING), VV_RO},
    {VV_NAME("scrollstart",	 VAR_STRING), 0},
    {VV_NAME("swapname",	 VAR_STRING), VV_RO},
    {VV_NAME("swapchoice",	 VAR_STRING), 0},
    {VV_NAME("swapcommand",	 VAR_STRING), VV_RO},
    {VV_NAME("char",		 VAR_STRING), 0},
    {VV_NAME("mouse_win",	 VAR_NUMBER), 0},
    {VV_NAME("mouse_winid",	 VAR_NUMBER), 0},
    {VV_NAME("mouse_lnum",	 VAR_NUMBER), 0},
    {VV_NAME("mouse_col",	 VAR_NUMBER), 0},
    {VV_NAME("operator",	 VAR_STRING), VV_RO},
    {VV_NAME("searchforward",	 VAR_NUMBER), 0},
    {VV_NAME("hlsearch",	 VAR_NUMBER), 0},
    {VV_NAME("oldfiles",	 VAR_LIST), 0},
    {VV_NAME("windowid",	 VAR_NUMBER), VV_RO},
    {VV_NAME("progpath",	 VAR_STRING), VV_RO},
    {VV_NAME("completed_item",	 VAR_DICT), VV_RO},
    {VV_NAME("option_new",	 VAR_STRING), VV_RO},
    {VV_NAME("option_old",	 VAR_STRING), VV_RO},
    {VV_NAME("option_oldlocal",	 VAR_STRING), VV_RO},
    {VV_NAME("option_oldglobal", VAR_STRING), VV_RO},
    {VV_NAME("option_command",	 VAR_STRING), VV_RO},
    {VV_NAME("option_type",	 VAR_STRING), VV_RO},
    {VV_NAME("errors",		 VAR_LIST), 0},
    {VV_NAME("false",		 VAR_BOOL), VV_RO},
    {VV_NAME("true",		 VAR_BOOL), VV_RO},
    {VV_NAME("none",		 VAR_SPECIAL), VV_RO},
    {VV_NAME("null",		 VAR_SPECIAL), VV_RO},
    {VV_NAME("numbersize",	 VAR_NUMBER), VV_RO},
    {VV_NAME("vim_did_enter",	 VAR_NUMBER), VV_RO},
    {VV_NAME("testing",		 VAR_NUMBER), 0},
    {VV_NAME("t_number",	 VAR_NUMBER), VV_RO},
    {VV_NAME("t_string",	 VAR_NUMBER), VV_RO},
    {VV_NAME("t_func",		 VAR_NUMBER), VV_RO},
    {VV_NAME("t_list",		 VAR_NUMBER), VV_RO},
    {VV_NAME("t_dict",		 VAR_NUMBER), VV_RO},
    {VV_NAME("t_float",		 VAR_NUMBER), VV_RO},
    {VV_NAME("t_bool",		 VAR_NUMBER), VV_RO},
    {VV_NAME("t_none",		 VAR_NUMBER), VV_RO},
    {VV_NAME("t_job",		 VAR_NUMBER), VV_RO},
    {VV_NAME("t_channel",	 VAR_NUMBER), VV_RO},
    {VV_NAME("t_blob",		 VAR_NUMBER), VV_RO},
    {VV_NAME("termrfgresp",	 VAR_STRING), VV_RO},
    {VV_NAME("termrbgresp",	 VAR_STRING), VV_RO},
    {VV_NAME("termu7resp",	 VAR_STRING), VV_RO},
    {VV_NAME("termstyleresp",	 VAR_STRING), VV_RO},
    {VV_NAME("termblinkresp",	 VAR_STRING), VV_RO},
    {VV_NAME("event",		 VAR_DICT), VV_RO},
    {VV_NAME("versionlong",	 VAR_NUMBER), VV_RO},
    {VV_NAME("echospace",	 VAR_NUMBER), VV_RO},
    {VV_NAME("argv",		 VAR_LIST), VV_RO},
    {VV_NAME("collate",		 VAR_STRING), VV_RO},
    {VV_NAME("disallow_let",	 VAR_NUMBER), 0}, // TODO: remove
};

// shorthand
#define vv_type		vv_di.di_tv.v_type
#define vv_nr		vv_di.di_tv.vval.v_number
#define vv_float	vv_di.di_tv.vval.v_float
#define vv_str		vv_di.di_tv.vval.v_string
#define vv_list		vv_di.di_tv.vval.v_list
#define vv_dict		vv_di.di_tv.vval.v_dict
#define vv_blob		vv_di.di_tv.vval.v_blob
#define vv_tv		vv_di.di_tv

static dictitem_T	vimvars_var;		// variable used for v:
static dict_T		vimvardict;		// Dictionary with v: variables
#define vimvarht  vimvardict.dv_hashtab

// for VIM_VERSION_ defines
#include "version.h"

static void list_glob_vars(int *first);
static void list_buf_vars(int *first);
static void list_win_vars(int *first);
static void list_tab_vars(int *first);
static char_u *list_arg_vars(exarg_T *eap, char_u *arg, int *first);
static char_u *ex_let_one(char_u *arg, typval_T *tv, int copy, int flags, char_u *endchars, char_u *op);
static int do_unlet_var(lval_T *lp, char_u *name_end, exarg_T *eap, int deep, void *cookie);
static int do_lock_var(lval_T *lp, char_u *name_end, exarg_T *eap, int deep, void *cookie);
static void list_one_var(dictitem_T *v, char *prefix, int *first);
static void list_one_var_a(char *prefix, char_u *name, int type, char_u *string, int *first);

/*
 * Initialize global and vim special variables
 */
    void
evalvars_init(void)
{
    int		    i;
    struct vimvar   *p;

    init_var_dict(&globvardict, &globvars_var, VAR_DEF_SCOPE);
    init_var_dict(&vimvardict, &vimvars_var, VAR_SCOPE);
    vimvardict.dv_lock = VAR_FIXED;
    hash_init(&compat_hashtab);

    for (i = 0; i < VV_LEN; ++i)
    {
	p = &vimvars[i];
	if (STRLEN(p->vv_name) > DICTITEM16_KEY_LEN)
	{
	    iemsg("INTERNAL: name too long, increase size of dictitem16_T");
	    getout(1);
	}
	STRCPY(p->vv_di.di_key, p->vv_name);
	if (p->vv_flags & VV_RO)
	    p->vv_di.di_flags = DI_FLAGS_RO | DI_FLAGS_FIX;
	else if (p->vv_flags & VV_RO_SBX)
	    p->vv_di.di_flags = DI_FLAGS_RO_SBX | DI_FLAGS_FIX;
	else
	    p->vv_di.di_flags = DI_FLAGS_FIX;

	// add to v: scope dict, unless the value is not always available
	if (p->vv_type != VAR_UNKNOWN)
	    hash_add(&vimvarht, p->vv_di.di_key);
	if (p->vv_flags & VV_COMPAT)
	    // add to compat scope dict
	    hash_add(&compat_hashtab, p->vv_di.di_key);
    }
    set_vim_var_nr(VV_VERSION, VIM_VERSION_100);
    set_vim_var_nr(VV_VERSIONLONG, VIM_VERSION_100 * 10000 + highest_patch());

    set_vim_var_nr(VV_SEARCHFORWARD, 1L);
    set_vim_var_nr(VV_HLSEARCH, 1L);
    set_vim_var_dict(VV_COMPLETED_ITEM, dict_alloc_lock(VAR_FIXED));
    set_vim_var_list(VV_ERRORS, list_alloc());
    set_vim_var_dict(VV_EVENT, dict_alloc_lock(VAR_FIXED));

    set_vim_var_nr(VV_FALSE, VVAL_FALSE);
    set_vim_var_nr(VV_TRUE, VVAL_TRUE);
    set_vim_var_nr(VV_NONE, VVAL_NONE);
    set_vim_var_nr(VV_NULL, VVAL_NULL);
    set_vim_var_nr(VV_NUMBERSIZE, sizeof(varnumber_T) * 8);

    set_vim_var_nr(VV_TYPE_NUMBER,  VAR_TYPE_NUMBER);
    set_vim_var_nr(VV_TYPE_STRING,  VAR_TYPE_STRING);
    set_vim_var_nr(VV_TYPE_FUNC,    VAR_TYPE_FUNC);
    set_vim_var_nr(VV_TYPE_LIST,    VAR_TYPE_LIST);
    set_vim_var_nr(VV_TYPE_DICT,    VAR_TYPE_DICT);
    set_vim_var_nr(VV_TYPE_FLOAT,   VAR_TYPE_FLOAT);
    set_vim_var_nr(VV_TYPE_BOOL,    VAR_TYPE_BOOL);
    set_vim_var_nr(VV_TYPE_NONE,    VAR_TYPE_NONE);
    set_vim_var_nr(VV_TYPE_JOB,     VAR_TYPE_JOB);
    set_vim_var_nr(VV_TYPE_CHANNEL, VAR_TYPE_CHANNEL);
    set_vim_var_nr(VV_TYPE_BLOB,    VAR_TYPE_BLOB);

    set_vim_var_nr(VV_ECHOSPACE,    sc_col - 1);

    // TODO: remove later
    set_vim_var_nr(VV_DISALLOW_LET, 1);

    // Default for v:register is not 0 but '"'.  This is adjusted once the
    // clipboard has been setup by calling reset_reg_var().
    set_reg_var(0);
}

#if defined(EXITFREE) || defined(PROTO)
/*
 * Free all vim variables information on exit
 */
    void
evalvars_clear(void)
{
    int		    i;
    struct vimvar   *p;

    for (i = 0; i < VV_LEN; ++i)
    {
	p = &vimvars[i];
	if (p->vv_di.di_tv.v_type == VAR_STRING)
	    VIM_CLEAR(p->vv_str);
	else if (p->vv_di.di_tv.v_type == VAR_LIST)
	{
	    list_unref(p->vv_list);
	    p->vv_list = NULL;
	}
    }
    hash_clear(&vimvarht);
    hash_init(&vimvarht);  // garbage_collect() will access it
    hash_clear(&compat_hashtab);

    // global variables
    vars_clear(&globvarht);

    // Script-local variables. Clear all the variables here.
    // The scriptvar_T is cleared later in free_scriptnames(), because a
    // variable in one script might hold a reference to the whole scope of
    // another script.
    for (i = 1; i <= script_items.ga_len; ++i)
	vars_clear(&SCRIPT_VARS(i));
}
#endif

    int
garbage_collect_globvars(int copyID)
{
    return set_ref_in_ht(&globvarht, copyID, NULL);
}

    int
garbage_collect_vimvars(int copyID)
{
    return set_ref_in_ht(&vimvarht, copyID, NULL);
}

    int
garbage_collect_scriptvars(int copyID)
{
    int		    i;
    int		    idx;
    int		    abort = FALSE;
    scriptitem_T    *si;

    for (i = 1; i <= script_items.ga_len; ++i)
    {
	abort = abort || set_ref_in_ht(&SCRIPT_VARS(i), copyID, NULL);

	si = SCRIPT_ITEM(i);
	for (idx = 0; idx < si->sn_var_vals.ga_len; ++idx)
	{
	    svar_T    *sv = ((svar_T *)si->sn_var_vals.ga_data) + idx;

	    abort = abort || set_ref_in_item(sv->sv_tv, copyID, NULL, NULL);
	}
    }

    return abort;
}

/*
 * Set an internal variable to a string value. Creates the variable if it does
 * not already exist.
 */
    void
set_internal_string_var(char_u *name, char_u *value)
{
    char_u	*val;
    typval_T	*tvp;

    val = vim_strsave(value);
    if (val != NULL)
    {
	tvp = alloc_string_tv(val);
	if (tvp != NULL)
	{
	    set_var(name, tvp, FALSE);
	    free_tv(tvp);
	}
    }
}

    int
eval_charconvert(
    char_u	*enc_from,
    char_u	*enc_to,
    char_u	*fname_from,
    char_u	*fname_to)
{
    int		err = FALSE;

    set_vim_var_string(VV_CC_FROM, enc_from, -1);
    set_vim_var_string(VV_CC_TO, enc_to, -1);
    set_vim_var_string(VV_FNAME_IN, fname_from, -1);
    set_vim_var_string(VV_FNAME_OUT, fname_to, -1);
    if (eval_to_bool(p_ccv, &err, NULL, FALSE))
	err = TRUE;
    set_vim_var_string(VV_CC_FROM, NULL, -1);
    set_vim_var_string(VV_CC_TO, NULL, -1);
    set_vim_var_string(VV_FNAME_IN, NULL, -1);
    set_vim_var_string(VV_FNAME_OUT, NULL, -1);

    if (err)
	return FAIL;
    return OK;
}

# if defined(FEAT_POSTSCRIPT) || defined(PROTO)
    int
eval_printexpr(char_u *fname, char_u *args)
{
    int		err = FALSE;

    set_vim_var_string(VV_FNAME_IN, fname, -1);
    set_vim_var_string(VV_CMDARG, args, -1);
    if (eval_to_bool(p_pexpr, &err, NULL, FALSE))
	err = TRUE;
    set_vim_var_string(VV_FNAME_IN, NULL, -1);
    set_vim_var_string(VV_CMDARG, NULL, -1);

    if (err)
    {
	mch_remove(fname);
	return FAIL;
    }
    return OK;
}
# endif

# if defined(FEAT_DIFF) || defined(PROTO)
    void
eval_diff(
    char_u	*origfile,
    char_u	*newfile,
    char_u	*outfile)
{
    int		err = FALSE;

    set_vim_var_string(VV_FNAME_IN, origfile, -1);
    set_vim_var_string(VV_FNAME_NEW, newfile, -1);
    set_vim_var_string(VV_FNAME_OUT, outfile, -1);
    (void)eval_to_bool(p_dex, &err, NULL, FALSE);
    set_vim_var_string(VV_FNAME_IN, NULL, -1);
    set_vim_var_string(VV_FNAME_NEW, NULL, -1);
    set_vim_var_string(VV_FNAME_OUT, NULL, -1);
}

    void
eval_patch(
    char_u	*origfile,
    char_u	*difffile,
    char_u	*outfile)
{
    int		err;

    set_vim_var_string(VV_FNAME_IN, origfile, -1);
    set_vim_var_string(VV_FNAME_DIFF, difffile, -1);
    set_vim_var_string(VV_FNAME_OUT, outfile, -1);
    (void)eval_to_bool(p_pex, &err, NULL, FALSE);
    set_vim_var_string(VV_FNAME_IN, NULL, -1);
    set_vim_var_string(VV_FNAME_DIFF, NULL, -1);
    set_vim_var_string(VV_FNAME_OUT, NULL, -1);
}
# endif

#if defined(FEAT_SPELL) || defined(PROTO)
/*
 * Evaluate an expression to a list with suggestions.
 * For the "expr:" part of 'spellsuggest'.
 * Returns NULL when there is an error.
 */
    list_T *
eval_spell_expr(char_u *badword, char_u *expr)
{
    typval_T	save_val;
    typval_T	rettv;
    list_T	*list = NULL;
    char_u	*p = skipwhite(expr);

    // Set "v:val" to the bad word.
    prepare_vimvar(VV_VAL, &save_val);
    set_vim_var_string(VV_VAL, badword, -1);
    if (p_verbose == 0)
	++emsg_off;

    if (eval1(&p, &rettv, &EVALARG_EVALUATE) == OK)
    {
	if (rettv.v_type != VAR_LIST)
	    clear_tv(&rettv);
	else
	    list = rettv.vval.v_list;
    }

    if (p_verbose == 0)
	--emsg_off;
    clear_tv(get_vim_var_tv(VV_VAL));
    restore_vimvar(VV_VAL, &save_val);

    return list;
}

/*
 * "list" is supposed to contain two items: a word and a number.  Return the
 * word in "pp" and the number as the return value.
 * Return -1 if anything isn't right.
 * Used to get the good word and score from the eval_spell_expr() result.
 */
    int
get_spellword(list_T *list, char_u **pp)
{
    listitem_T	*li;

    li = list->lv_first;
    if (li == NULL)
	return -1;
    *pp = tv_get_string(&li->li_tv);

    li = li->li_next;
    if (li == NULL)
	return -1;
    return (int)tv_get_number(&li->li_tv);
}
#endif

/*
 * Prepare v: variable "idx" to be used.
 * Save the current typeval in "save_tv" and clear it.
 * When not used yet add the variable to the v: hashtable.
 */
    void
prepare_vimvar(int idx, typval_T *save_tv)
{
    *save_tv = vimvars[idx].vv_tv;
    vimvars[idx].vv_str = NULL;  // don't free it now
    if (vimvars[idx].vv_type == VAR_UNKNOWN)
	hash_add(&vimvarht, vimvars[idx].vv_di.di_key);
}

/*
 * Restore v: variable "idx" to typeval "save_tv".
 * Note that the v: variable must have been cleared already.
 * When no longer defined, remove the variable from the v: hashtable.
 */
    void
restore_vimvar(int idx, typval_T *save_tv)
{
    hashitem_T	*hi;

    vimvars[idx].vv_tv = *save_tv;
    if (vimvars[idx].vv_type == VAR_UNKNOWN)
    {
	hi = hash_find(&vimvarht, vimvars[idx].vv_di.di_key);
	if (HASHITEM_EMPTY(hi))
	    internal_error("restore_vimvar()");
	else
	    hash_remove(&vimvarht, hi);
    }
}

/*
 * List Vim variables.
 */
    static void
list_vim_vars(int *first)
{
    list_hashtable_vars(&vimvarht, "v:", FALSE, first);
}

/*
 * List script-local variables, if there is a script.
 */
    static void
list_script_vars(int *first)
{
    if (SCRIPT_ID_VALID(current_sctx.sc_sid))
	list_hashtable_vars(&SCRIPT_VARS(current_sctx.sc_sid),
							   "s:", FALSE, first);
}

/*
 * Get a list of lines from a HERE document. The here document is a list of
 * lines surrounded by a marker.
 *	cmd << {marker}
 *	  {line1}
 *	  {line2}
 *	  ....
 *	{marker}
 *
 * The {marker} is a string. If the optional 'trim' word is supplied before the
 * marker, then the leading indentation before the lines (matching the
 * indentation in the 'cmd' line) is stripped.
 *
 * When getting lines for an embedded script (e.g. python, lua, perl, ruby,
 * tcl, mzscheme), script_get is set to TRUE. In this case, if the marker is
 * missing, then '.' is accepted as a marker.
 *
 * Returns a List with {lines} or NULL.
 */
    list_T *
heredoc_get(exarg_T *eap, char_u *cmd, int script_get)
{
    char_u	*theline;
    char_u	*marker;
    list_T	*l;
    char_u	*p;
    int		marker_indent_len = 0;
    int		text_indent_len = 0;
    char_u	*text_indent = NULL;
    char_u	dot[] = ".";
    int		comment_char = in_vim9script() ? '#' : '"';

    if (eap->getline == NULL)
    {
	emsg(_("E991: cannot use =<< here"));
	return NULL;
    }

    // Check for the optional 'trim' word before the marker
    cmd = skipwhite(cmd);
    if (STRNCMP(cmd, "trim", 4) == 0 && (cmd[4] == NUL || VIM_ISWHITE(cmd[4])))
    {
	cmd = skipwhite(cmd + 4);

	// Trim the indentation from all the lines in the here document.
	// The amount of indentation trimmed is the same as the indentation of
	// the first line after the :let command line.  To find the end marker
	// the indent of the :let command line is trimmed.
	p = *eap->cmdlinep;
	while (VIM_ISWHITE(*p))
	{
	    p++;
	    marker_indent_len++;
	}
	text_indent_len = -1;
    }

    // The marker is the next word.
    if (*cmd != NUL && *cmd != comment_char)
    {
	marker = skipwhite(cmd);
	p = skiptowhite(marker);
	if (*skipwhite(p) != NUL && *skipwhite(p) != comment_char)
	{
	    semsg(_(e_trailing_arg), p);
	    return NULL;
	}
	*p = NUL;
	if (!script_get && vim_islower(*marker))
	{
	    emsg(_("E221: Marker cannot start with lower case letter"));
	    return NULL;
	}
    }
    else
    {
	// When getting lines for an embedded script, if the marker is missing,
	// accept '.' as the marker.
	if (script_get)
	    marker = dot;
	else
	{
	    emsg(_("E172: Missing marker"));
	    return NULL;
	}
    }

    l = list_alloc();
    if (l == NULL)
	return NULL;

    for (;;)
    {
	int	mi = 0;
	int	ti = 0;

	theline = eap->getline(NUL, eap->cookie, 0, FALSE);
	if (theline == NULL)
	{
	    semsg(_("E990: Missing end marker '%s'"), marker);
	    break;
	}

	// with "trim": skip the indent matching the :let line to find the
	// marker
	if (marker_indent_len > 0
		&& STRNCMP(theline, *eap->cmdlinep, marker_indent_len) == 0)
	    mi = marker_indent_len;
	if (STRCMP(marker, theline + mi) == 0)
	{
	    vim_free(theline);
	    break;
	}

	if (text_indent_len == -1 && *theline != NUL)
	{
	    // set the text indent from the first line.
	    p = theline;
	    text_indent_len = 0;
	    while (VIM_ISWHITE(*p))
	    {
		p++;
		text_indent_len++;
	    }
	    text_indent = vim_strnsave(theline, text_indent_len);
	}
	// with "trim": skip the indent matching the first line
	if (text_indent != NULL)
	    for (ti = 0; ti < text_indent_len; ++ti)
		if (theline[ti] != text_indent[ti])
		    break;

	if (list_append_string(l, theline + ti, -1) == FAIL)
	    break;
	vim_free(theline);
    }
    vim_free(text_indent);

    return l;
}

/*
 * Vim9 variable declaration:
 * ":var name"
 * ":var name: type"
 * ":var name = expr"
 * ":var name: type = expr"
 * etc.
 */
    void
ex_var(exarg_T *eap)
{
    if (!in_vim9script())
    {
	semsg(_(e_str_cannot_be_used_in_legacy_vim_script), ":var");
	return;
    }
    ex_let(eap);
}

/*
 * ":let"			list all variable values
 * ":let var1 var2"		list variable values
 * ":let var = expr"		assignment command.
 * ":let var += expr"		assignment command.
 * ":let var -= expr"		assignment command.
 * ":let var *= expr"		assignment command.
 * ":let var /= expr"		assignment command.
 * ":let var %= expr"		assignment command.
 * ":let var .= expr"		assignment command.
 * ":let var ..= expr"		assignment command.
 * ":let [var1, var2] = expr"	unpack list.
 * ":let var =<< ..."		heredoc
 * ":let var: string"		Vim9 declaration
 *
 * ":final var = expr"		assignment command.
 * ":final [var1, var2] = expr"	unpack list.
 *
 * ":const"			list all variable values
 * ":const var1 var2"		list variable values
 * ":const var = expr"		assignment command.
 * ":const [var1, var2] = expr"	unpack list.
 */
    void
ex_let(exarg_T *eap)
{
    char_u	*arg = eap->arg;
    char_u	*expr = NULL;
    typval_T	rettv;
    int		i;
    int		var_count = 0;
    int		semicolon = 0;
    char_u	op[4];
    char_u	*argend;
    int		first = TRUE;
    int		concat;
    int		has_assign;
    int		flags = eap->cmdidx == CMD_const ? ASSIGN_CONST : 0;
    int		vim9script = in_vim9script();

    if (eap->cmdidx == CMD_final && !vim9script)
    {
	    // In legacy Vim script ":final" is short for ":finally".
	    ex_finally(eap);
	    return;
    }
    if (get_vim_var_nr(VV_DISALLOW_LET)
				      && eap->cmdidx == CMD_let && vim9script)
    {
	emsg(_(e_cannot_use_let_in_vim9_script));
	return;
    }
    if (eap->cmdidx == CMD_const && !vim9script && !eap->forceit)
	// In legacy Vim script ":const" works like ":final".
	eap->cmdidx = CMD_final;

    // detect Vim9 assignment without ":let" or ":const"
    if (eap->arg == eap->cmd)
	flags |= ASSIGN_NO_DECL;

    argend = skip_var_list(arg, TRUE, &var_count, &semicolon, FALSE);
    if (argend == NULL)
	return;
    if (argend > arg && argend[-1] == '.')  // for var.='str'
	--argend;
    expr = skipwhite(argend);
    concat = expr[0] == '.'
	&& ((expr[1] == '=' && current_sctx.sc_version < 2)
		|| (expr[1] == '.' && expr[2] == '='));
    has_assign =  *expr == '=' || (vim_strchr((char_u *)"+-*/%", *expr) != NULL
							    && expr[1] == '=');
    if (!has_assign && !concat)
    {
	// ":let" without "=": list variables
	if (*arg == '[')
	    emsg(_(e_invarg));
	else if (expr[0] == '.' && expr[1] == '=')
	    emsg(_("E985: .= is not supported with script version >= 2"));
	else if (!ends_excmd2(eap->cmd, arg))
	{
	    if (vim9script)
	    {
		// Vim9 declaration ":let var: type"
		arg = vim9_declare_scriptvar(eap, arg);
	    }
	    else
	    {
		// ":let var1 var2" - list values
		arg = list_arg_vars(eap, arg, &first);
	    }
	}
	else if (!eap->skip)
	{
	    // ":let"
	    list_glob_vars(&first);
	    list_buf_vars(&first);
	    list_win_vars(&first);
	    list_tab_vars(&first);
	    list_script_vars(&first);
	    list_func_vars(&first);
	    list_vim_vars(&first);
	}
	eap->nextcmd = check_nextcmd(arg);
    }
    else if (expr[0] == '=' && expr[1] == '<' && expr[2] == '<')
    {
	list_T	*l;

	// HERE document
	l = heredoc_get(eap, expr + 3, FALSE);
	if (l != NULL)
	{
	    rettv_list_set(&rettv, l);
	    if (!eap->skip)
	    {
		op[0] = '=';
		op[1] = NUL;
		(void)ex_let_vars(eap->arg, &rettv, FALSE, semicolon, var_count,
								flags, op);
	    }
	    clear_tv(&rettv);
	}
    }
    else
    {
	evalarg_T   evalarg;
	int	    len = 1;

	CLEAR_FIELD(rettv);
	i = FAIL;
	if (has_assign || concat)
	{
	    op[0] = '=';
	    op[1] = NUL;
	    if (*expr != '=')
	    {
		if (vim9script && (flags & ASSIGN_NO_DECL) == 0)
		{
		    // +=, /=, etc. require an existing variable
		    semsg(_(e_cannot_use_operator_on_new_variable), eap->arg);
		    i = FAIL;
		}
		else if (vim_strchr((char_u *)"+-*/%.", *expr) != NULL)
		{
		    op[0] = *expr;   // +=, -=, *=, /=, %= or .=
		    ++len;
		    if (expr[0] == '.' && expr[1] == '.') // ..=
		    {
			++expr;
			++len;
		    }
		}
		expr += 2;
	    }
	    else
		++expr;

	    if (vim9script && (!VIM_ISWHITE(*argend)
						   || !IS_WHITE_OR_NUL(*expr)))
	    {
		vim_strncpy(op, expr - len, len);
		semsg(_(e_white_space_required_before_and_after_str), op);
		i = FAIL;
	    }

	    if (eap->skip)
		++emsg_skip;
	    CLEAR_FIELD(evalarg);
	    evalarg.eval_flags = eap->skip ? 0 : EVAL_EVALUATE;
	    if (getline_equal(eap->getline, eap->cookie, getsourceline))
	    {
		evalarg.eval_getline = eap->getline;
		evalarg.eval_cookie = eap->cookie;
	    }
	    expr = skipwhite_and_linebreak(expr, &evalarg);
	    i = eval0(expr, &rettv, eap, &evalarg);
	    if (eap->skip)
		--emsg_skip;
	    clear_evalarg(&evalarg, eap);
	}
	if (eap->skip)
	{
	    if (i != FAIL)
		clear_tv(&rettv);
	}
	else if (i != FAIL)
	{
	    (void)ex_let_vars(eap->arg, &rettv, FALSE, semicolon, var_count,
								    flags, op);
	    clear_tv(&rettv);
	}
    }
}

/*
 * Assign the typevalue "tv" to the variable or variables at "arg_start".
 * Handles both "var" with any type and "[var, var; var]" with a list type.
 * When "op" is not NULL it points to a string with characters that
 * must appear after the variable(s).  Use "+", "-" or "." for add, subtract
 * or concatenate.
 * Returns OK or FAIL;
 */
    int
ex_let_vars(
    char_u	*arg_start,
    typval_T	*tv,
    int		copy,		// copy values from "tv", don't move
    int		semicolon,	// from skip_var_list()
    int		var_count,	// from skip_var_list()
    int		flags,		// ASSIGN_CONST, ASSIGN_NO_DECL
    char_u	*op)
{
    char_u	*arg = arg_start;
    list_T	*l;
    int		i;
    listitem_T	*item;
    typval_T	ltv;

    if (*arg != '[')
    {
	// ":let var = expr" or ":for var in list"
	if (ex_let_one(arg, tv, copy, flags, op, op) == NULL)
	    return FAIL;
	return OK;
    }

    // ":let [v1, v2] = list" or ":for [v1, v2] in listlist"
    if (tv->v_type != VAR_LIST || (l = tv->vval.v_list) == NULL)
    {
	emsg(_(e_listreq));
	return FAIL;
    }

    i = list_len(l);
    if (semicolon == 0 && var_count < i)
    {
	emsg(_("E687: Less targets than List items"));
	return FAIL;
    }
    if (var_count - semicolon > i)
    {
	emsg(_("E688: More targets than List items"));
	return FAIL;
    }

    CHECK_LIST_MATERIALIZE(l);
    item = l->lv_first;
    while (*arg != ']')
    {
	arg = skipwhite(arg + 1);
	arg = ex_let_one(arg, &item->li_tv, TRUE, flags, (char_u *)",;]", op);
	item = item->li_next;
	if (arg == NULL)
	    return FAIL;

	arg = skipwhite(arg);
	if (*arg == ';')
	{
	    // Put the rest of the list (may be empty) in the var after ';'.
	    // Create a new list for this.
	    l = list_alloc();
	    if (l == NULL)
		return FAIL;
	    while (item != NULL)
	    {
		list_append_tv(l, &item->li_tv);
		item = item->li_next;
	    }

	    ltv.v_type = VAR_LIST;
	    ltv.v_lock = 0;
	    ltv.vval.v_list = l;
	    l->lv_refcount = 1;

	    arg = ex_let_one(skipwhite(arg + 1), &ltv, FALSE, flags,
							    (char_u *)"]", op);
	    clear_tv(&ltv);
	    if (arg == NULL)
		return FAIL;
	    break;
	}
	else if (*arg != ',' && *arg != ']')
	{
	    internal_error("ex_let_vars()");
	    return FAIL;
	}
    }

    return OK;
}

/*
 * Skip over assignable variable "var" or list of variables "[var, var]".
 * Used for ":let varvar = expr" and ":for varvar in expr".
 * For "[var, var]" increment "*var_count" for each variable.
 * for "[var, var; var]" set "semicolon" to 1.
 * If "silent" is TRUE do not give an "invalid argument" error message.
 * Return NULL for an error.
 */
    char_u *
skip_var_list(
    char_u	*arg,
    int		include_type,
    int		*var_count,
    int		*semicolon,
    int		silent)
{
    char_u	*p, *s;

    if (*arg == '[')
    {
	// "[var, var]": find the matching ']'.
	p = arg;
	for (;;)
	{
	    p = skipwhite(p + 1);	// skip whites after '[', ';' or ','
	    s = skip_var_one(p, FALSE);
	    if (s == p)
	    {
		if (!silent)
		    semsg(_(e_invarg2), p);
		return NULL;
	    }
	    ++*var_count;

	    p = skipwhite(s);
	    if (*p == ']')
		break;
	    else if (*p == ';')
	    {
		if (*semicolon == 1)
		{
		    emsg(_("E452: Double ; in list of variables"));
		    return NULL;
		}
		*semicolon = 1;
	    }
	    else if (*p != ',')
	    {
		if (!silent)
		    semsg(_(e_invarg2), p);
		return NULL;
	    }
	}
	return p + 1;
    }
    else
	return skip_var_one(arg, include_type);
}

/*
 * Skip one (assignable) variable name, including @r, $VAR, &option, d.key,
 * l[idx].
 * In Vim9 script also skip over ": type" if "include_type" is TRUE.
 */
    char_u *
skip_var_one(char_u *arg, int include_type)
{
    char_u *end;

    if (*arg == '@' && arg[1] != NUL)
	return arg + 2;
    end = find_name_end(*arg == '$' || *arg == '&' ? arg + 1 : arg,
				   NULL, NULL, FNE_INCL_BR | FNE_CHECK_START);
    if (include_type && in_vim9script())
    {
	// "a: type" is declaring variable "a" with a type, not "a:".
	if (end == arg + 2 && end[-1] == ':')
	    --end;
	if (*end == ':')
	    end = skip_type(skipwhite(end + 1), FALSE);
    }
    return end;
}

/*
 * List variables for hashtab "ht" with prefix "prefix".
 * If "empty" is TRUE also list NULL strings as empty strings.
 */
    void
list_hashtable_vars(
    hashtab_T	*ht,
    char	*prefix,
    int		empty,
    int		*first)
{
    hashitem_T	*hi;
    dictitem_T	*di;
    int		todo;
    char_u	buf[IOSIZE];

    todo = (int)ht->ht_used;
    for (hi = ht->ht_array; todo > 0 && !got_int; ++hi)
    {
	if (!HASHITEM_EMPTY(hi))
	{
	    --todo;
	    di = HI2DI(hi);

	    // apply :filter /pat/ to variable name
	    vim_strncpy((char_u *)buf, (char_u *)prefix, IOSIZE - 1);
	    vim_strcat((char_u *)buf, di->di_key, IOSIZE);
	    if (message_filtered(buf))
		continue;

	    if (empty || di->di_tv.v_type != VAR_STRING
					   || di->di_tv.vval.v_string != NULL)
		list_one_var(di, prefix, first);
	}
    }
}

/*
 * List global variables.
 */
    static void
list_glob_vars(int *first)
{
    list_hashtable_vars(&globvarht, "", TRUE, first);
}

/*
 * List buffer variables.
 */
    static void
list_buf_vars(int *first)
{
    list_hashtable_vars(&curbuf->b_vars->dv_hashtab, "b:", TRUE, first);
}

/*
 * List window variables.
 */
    static void
list_win_vars(int *first)
{
    list_hashtable_vars(&curwin->w_vars->dv_hashtab, "w:", TRUE, first);
}

/*
 * List tab page variables.
 */
    static void
list_tab_vars(int *first)
{
    list_hashtable_vars(&curtab->tp_vars->dv_hashtab, "t:", TRUE, first);
}

/*
 * List variables in "arg".
 */
    static char_u *
list_arg_vars(exarg_T *eap, char_u *arg, int *first)
{
    int		error = FALSE;
    int		len;
    char_u	*name;
    char_u	*name_start;
    char_u	*arg_subsc;
    char_u	*tofree;
    typval_T    tv;

    while (!ends_excmd2(eap->cmd, arg) && !got_int)
    {
	if (error || eap->skip)
	{
	    arg = find_name_end(arg, NULL, NULL, FNE_INCL_BR | FNE_CHECK_START);
	    if (!VIM_ISWHITE(*arg) && !ends_excmd(*arg))
	    {
		emsg_severe = TRUE;
		semsg(_(e_trailing_arg), arg);
		break;
	    }
	}
	else
	{
	    // get_name_len() takes care of expanding curly braces
	    name_start = name = arg;
	    len = get_name_len(&arg, &tofree, TRUE, TRUE);
	    if (len <= 0)
	    {
		// This is mainly to keep test 49 working: when expanding
		// curly braces fails overrule the exception error message.
		if (len < 0 && !aborting())
		{
		    emsg_severe = TRUE;
		    semsg(_(e_invarg2), arg);
		    break;
		}
		error = TRUE;
	    }
	    else
	    {
		arg = skipwhite(arg);
		if (tofree != NULL)
		    name = tofree;
		if (eval_variable(name, len, &tv, NULL, TRUE, FALSE) == FAIL)
		    error = TRUE;
		else
		{
		    // handle d.key, l[idx], f(expr)
		    arg_subsc = arg;
		    if (handle_subscript(&arg, &tv, &EVALARG_EVALUATE, TRUE)
								       == FAIL)
			error = TRUE;
		    else
		    {
			if (arg == arg_subsc && len == 2 && name[1] == ':')
			{
			    switch (*name)
			    {
				case 'g': list_glob_vars(first); break;
				case 'b': list_buf_vars(first); break;
				case 'w': list_win_vars(first); break;
				case 't': list_tab_vars(first); break;
				case 'v': list_vim_vars(first); break;
				case 's': list_script_vars(first); break;
				case 'l': list_func_vars(first); break;
				default:
					  semsg(_("E738: Can't list variables for %s"), name);
			    }
			}
			else
			{
			    char_u	numbuf[NUMBUFLEN];
			    char_u	*tf;
			    int		c;
			    char_u	*s;

			    s = echo_string(&tv, &tf, numbuf, 0);
			    c = *arg;
			    *arg = NUL;
			    list_one_var_a("",
				    arg == arg_subsc ? name : name_start,
				    tv.v_type,
				    s == NULL ? (char_u *)"" : s,
				    first);
			    *arg = c;
			    vim_free(tf);
			}
			clear_tv(&tv);
		    }
		}
	    }

	    vim_free(tofree);
	}

	arg = skipwhite(arg);
    }

    return arg;
}

/*
 * Set one item of ":let var = expr" or ":let [v1, v2] = list" to its value.
 * Returns a pointer to the char just after the var name.
 * Returns NULL if there is an error.
 */
    static char_u *
ex_let_one(
    char_u	*arg,		// points to variable name
    typval_T	*tv,		// value to assign to variable
    int		copy,		// copy value from "tv"
    int		flags,		// ASSIGN_CONST, ASSIGN_NO_DECL
    char_u	*endchars,	// valid chars after variable name  or NULL
    char_u	*op)		// "+", "-", "."  or NULL
{
    int		c1;
    char_u	*name;
    char_u	*p;
    char_u	*arg_end = NULL;
    int		len;
    int		opt_flags;
    char_u	*tofree = NULL;

    if (in_vim9script() && (flags & ASSIGN_NO_DECL) == 0
				  && vim_strchr((char_u *)"$@&", *arg) != NULL)
    {
	vim9_declare_error(arg);
	return NULL;
    }

    // ":let $VAR = expr": Set environment variable.
    if (*arg == '$')
    {
	if (flags & ASSIGN_CONST)
	{
	    emsg(_("E996: Cannot lock an environment variable"));
	    return NULL;
	}

	// Find the end of the name.
	++arg;
	name = arg;
	len = get_env_len(&arg);
	if (len == 0)
	    semsg(_(e_invarg2), name - 1);
	else
	{
	    if (op != NULL && vim_strchr((char_u *)"+-*/%", *op) != NULL)
		semsg(_(e_letwrong), op);
	    else if (endchars != NULL
			     && vim_strchr(endchars, *skipwhite(arg)) == NULL)
		emsg(_(e_letunexp));
	    else if (!check_secure())
	    {
		c1 = name[len];
		name[len] = NUL;
		p = tv_get_string_chk(tv);
		if (p != NULL && op != NULL && *op == '.')
		{
		    int	    mustfree = FALSE;
		    char_u  *s = vim_getenv(name, &mustfree);

		    if (s != NULL)
		    {
			p = tofree = concat_str(s, p);
			if (mustfree)
			    vim_free(s);
		    }
		}
		if (p != NULL)
		{
		    vim_setenv_ext(name, p);
		    arg_end = arg;
		}
		name[len] = c1;
		vim_free(tofree);
	    }
	}
    }

    // ":let &option = expr": Set option value.
    // ":let &l:option = expr": Set local option value.
    // ":let &g:option = expr": Set global option value.
    else if (*arg == '&')
    {
	if (flags & ASSIGN_CONST)
	{
	    emsg(_(e_const_option));
	    return NULL;
	}
	// Find the end of the name.
	p = find_option_end(&arg, &opt_flags);
	if (p == NULL || (endchars != NULL
			      && vim_strchr(endchars, *skipwhite(p)) == NULL))
	    emsg(_(e_letunexp));
	else
	{
	    long	n = 0;
	    int		opt_type;
	    long	numval;
	    char_u	*stringval = NULL;
	    char_u	*s = NULL;
	    int		failed = FALSE;

	    c1 = *p;
	    *p = NUL;

	    opt_type = get_option_value(arg, &numval, &stringval, opt_flags);
	    if ((opt_type == 1 || opt_type == -1)
			     && (tv->v_type != VAR_STRING || !in_vim9script()))
		// number, possibly hidden
		n = (long)tv_get_number(tv);

	    // Avoid setting a string option to the text "v:false" or similar.
	    // In Vim9 script also don't convert a number to string.
	    if (tv->v_type != VAR_BOOL && tv->v_type != VAR_SPECIAL
			     && (!in_vim9script() || tv->v_type != VAR_NUMBER))
		s = tv_get_string_chk(tv);

	    if (op != NULL && *op != '=')
	    {
		if ((opt_type == 1 && *op == '.')
			|| (opt_type == 0 && *op != '.'))
		{
		    semsg(_(e_letwrong), op);
		    failed = TRUE;  // don't set the value

		}
		else
		{
		    if (opt_type == 1)  // number
		    {
			switch (*op)
			{
			    case '+': n = numval + n; break;
			    case '-': n = numval - n; break;
			    case '*': n = numval * n; break;
			    case '/': n = (long)num_divide(numval, n); break;
			    case '%': n = (long)num_modulus(numval, n); break;
			}
		    }
		    else if (opt_type == 0 && stringval != NULL && s != NULL)
		    {
			// string
			s = concat_str(stringval, s);
			vim_free(stringval);
			stringval = s;
		    }
		}
	    }

	    if (!failed)
	    {
		if (opt_type != 0 || s != NULL)
		{
		    set_option_value(arg, n, s, opt_flags);
		    arg_end = p;
		}
		else
		    emsg(_(e_stringreq));
	    }
	    *p = c1;
	    vim_free(stringval);
	}
    }

    // ":let @r = expr": Set register contents.
    else if (*arg == '@')
    {
	if (flags & ASSIGN_CONST)
	{
	    emsg(_("E996: Cannot lock a register"));
	    return NULL;
	}
	++arg;
	if (op != NULL && vim_strchr((char_u *)"+-*/%", *op) != NULL)
	    semsg(_(e_letwrong), op);
	else if (endchars != NULL
			 && vim_strchr(endchars, *skipwhite(arg + 1)) == NULL)
	    emsg(_(e_letunexp));
	else
	{
	    char_u	*ptofree = NULL;
	    char_u	*s;

	    p = tv_get_string_chk(tv);
	    if (p != NULL && op != NULL && *op == '.')
	    {
		s = get_reg_contents(*arg == '@' ? '"' : *arg, GREG_EXPR_SRC);
		if (s != NULL)
		{
		    p = ptofree = concat_str(s, p);
		    vim_free(s);
		}
	    }
	    if (p != NULL)
	    {
		write_reg_contents(*arg == '@' ? '"' : *arg, p, -1, FALSE);
		arg_end = arg + 1;
	    }
	    vim_free(ptofree);
	}
    }

    // ":let var = expr": Set internal variable.
    // ":let var: type = expr": Set internal variable with type.
    // ":let {expr} = expr": Idem, name made with curly braces
    else if (eval_isnamec1(*arg) || *arg == '{')
    {
	lval_T	lv;

	p = get_lval(arg, tv, &lv, FALSE, FALSE, 0, FNE_CHECK_START);
	if (p != NULL && lv.ll_name != NULL)
	{
	    if (endchars != NULL && vim_strchr(endchars,
					   *skipwhite(lv.ll_name_end)) == NULL)
		emsg(_(e_letunexp));
	    else
	    {
		set_var_lval(&lv, p, tv, copy, flags, op);
		arg_end = p;
	    }
	}
	clear_lval(&lv);
    }

    else
	semsg(_(e_invarg2), arg);

    return arg_end;
}

/*
 * ":unlet[!] var1 ... " command.
 */
    void
ex_unlet(exarg_T *eap)
{
    ex_unletlock(eap, eap->arg, 0, 0, do_unlet_var, NULL);
}

/*
 * ":lockvar" and ":unlockvar" commands
 */
    void
ex_lockvar(exarg_T *eap)
{
    char_u	*arg = eap->arg;
    int		deep = 2;

    if (eap->forceit)
	deep = -1;
    else if (vim_isdigit(*arg))
    {
	deep = getdigits(&arg);
	arg = skipwhite(arg);
    }

    ex_unletlock(eap, arg, deep, 0, do_lock_var, NULL);
}

/*
 * ":unlet", ":lockvar" and ":unlockvar" are quite similar.
 * Also used for Vim9 script.  "callback" is invoked as:
 *	callback(&lv, name_end, eap, deep, cookie)
 */
    void
ex_unletlock(
    exarg_T	*eap,
    char_u	*argstart,
    int		deep,
    int		glv_flags,
    int		(*callback)(lval_T *, char_u *, exarg_T *, int, void *),
    void	*cookie)
{
    char_u	*arg = argstart;
    char_u	*name_end;
    int		error = FALSE;
    lval_T	lv;

    do
    {
	if (*arg == '$')
	{
	    lv.ll_name = arg;
	    lv.ll_tv = NULL;
	    ++arg;
	    if (get_env_len(&arg) == 0)
	    {
		semsg(_(e_invarg2), arg - 1);
		return;
	    }
	    if (!error && !eap->skip
			      && callback(&lv, arg, eap, deep, cookie) == FAIL)
		error = TRUE;
	    name_end = arg;
	}
	else
	{
	    // Parse the name and find the end.
	    name_end = get_lval(arg, NULL, &lv, TRUE, eap->skip || error,
						   glv_flags, FNE_CHECK_START);
	    if (lv.ll_name == NULL)
		error = TRUE;	    // error but continue parsing
	    if (name_end == NULL || (!VIM_ISWHITE(*name_end)
						    && !ends_excmd(*name_end)))
	    {
		if (name_end != NULL)
		{
		    emsg_severe = TRUE;
		    semsg(_(e_trailing_arg), name_end);
		}
		if (!(eap->skip || error))
		    clear_lval(&lv);
		break;
	    }

	    if (!error && !eap->skip
			 && callback(&lv, name_end, eap, deep, cookie) == FAIL)
		error = TRUE;

	    if (!eap->skip)
		clear_lval(&lv);
	}

	arg = skipwhite(name_end);
    } while (!ends_excmd2(name_end, arg));

    eap->nextcmd = check_nextcmd(arg);
}

    static int
do_unlet_var(
    lval_T	*lp,
    char_u	*name_end,
    exarg_T	*eap,
    int		deep UNUSED,
    void	*cookie UNUSED)
{
    int		forceit = eap->forceit;
    int		ret = OK;
    int		cc;

    if (lp->ll_tv == NULL)
    {
	cc = *name_end;
	*name_end = NUL;

	// Environment variable, normal name or expanded name.
	if (*lp->ll_name == '$')
	    vim_unsetenv(lp->ll_name + 1);
	else if (do_unlet(lp->ll_name, forceit) == FAIL)
	    ret = FAIL;
	*name_end = cc;
    }
    else if ((lp->ll_list != NULL
		 && value_check_lock(lp->ll_list->lv_lock, lp->ll_name, FALSE))
	    || (lp->ll_dict != NULL
		&& value_check_lock(lp->ll_dict->dv_lock, lp->ll_name, FALSE)))
	return FAIL;
    else if (lp->ll_range)
    {
	listitem_T    *li;
	listitem_T    *ll_li = lp->ll_li;
	int	      ll_n1 = lp->ll_n1;

	while (ll_li != NULL && (lp->ll_empty2 || lp->ll_n2 >= ll_n1))
	{
	    li = ll_li->li_next;
	    if (value_check_lock(ll_li->li_tv.v_lock, lp->ll_name, FALSE))
		return FAIL;
	    ll_li = li;
	    ++ll_n1;
	}

	// Delete a range of List items.
	while (lp->ll_li != NULL && (lp->ll_empty2 || lp->ll_n2 >= lp->ll_n1))
	{
	    li = lp->ll_li->li_next;
	    listitem_remove(lp->ll_list, lp->ll_li);
	    lp->ll_li = li;
	    ++lp->ll_n1;
	}
    }
    else
    {
	if (lp->ll_list != NULL)
	    // unlet a List item.
	    listitem_remove(lp->ll_list, lp->ll_li);
	else
	    // unlet a Dictionary item.
	    dictitem_remove(lp->ll_dict, lp->ll_di);
    }

    return ret;
}

/*
 * "unlet" a variable.  Return OK if it existed, FAIL if not.
 * When "forceit" is TRUE don't complain if the variable doesn't exist.
 */
    int
do_unlet(char_u *name, int forceit)
{
    hashtab_T	*ht;
    hashitem_T	*hi;
    char_u	*varname;
    dict_T	*d;
    dictitem_T	*di;

    if (in_vim9script() && check_vim9_unlet(name) == FAIL)
	return FAIL;

    ht = find_var_ht(name, &varname);
    if (ht != NULL && *varname != NUL)
    {
	d = get_current_funccal_dict(ht);
	if (d == NULL)
	{
	    if (ht == &globvarht)
		d = &globvardict;
	    else if (ht == &compat_hashtab)
		d = &vimvardict;
	    else
	    {
		di = find_var_in_ht(ht, *name, (char_u *)"", FALSE);
		d = di == NULL ? NULL : di->di_tv.vval.v_dict;
	    }
	    if (d == NULL)
	    {
		internal_error("do_unlet()");
		return FAIL;
	    }
	}
	hi = hash_find(ht, varname);
	if (HASHITEM_EMPTY(hi))
	    hi = find_hi_in_scoped_ht(name, &ht);
	if (hi != NULL && !HASHITEM_EMPTY(hi))
	{
	    di = HI2DI(hi);
	    if (var_check_fixed(di->di_flags, name, FALSE)
		    || var_check_ro(di->di_flags, name, FALSE)
		    || value_check_lock(d->dv_lock, name, FALSE))
		return FAIL;

	    delete_var(ht, hi);
	    return OK;
	}
    }
    if (forceit)
	return OK;
    semsg(_("E108: No such variable: \"%s\""), name);
    return FAIL;
}

/*
 * Lock or unlock variable indicated by "lp".
 * "deep" is the levels to go (-1 for unlimited);
 * "lock" is TRUE for ":lockvar", FALSE for ":unlockvar".
 */
    static int
do_lock_var(
    lval_T	*lp,
    char_u	*name_end,
    exarg_T	*eap,
    int		deep,
    void	*cookie UNUSED)
{
    int		lock = eap->cmdidx == CMD_lockvar;
    int		ret = OK;
    int		cc;
    dictitem_T	*di;

    if (lp->ll_tv == NULL)
    {
	cc = *name_end;
	*name_end = NUL;
	if (*lp->ll_name == '$')
	{
	    semsg(_(e_lock_unlock), lp->ll_name);
	    ret = FAIL;
	}
	else
	{
	    // Normal name or expanded name.
	    di = find_var(lp->ll_name, NULL, TRUE);
	    if (di == NULL)
		ret = FAIL;
	    else if ((di->di_flags & DI_FLAGS_FIX)
			    && di->di_tv.v_type != VAR_DICT
			    && di->di_tv.v_type != VAR_LIST)
	    {
		// For historic reasons this error is not given for a list or
		// dict.  E.g., the b: dict could be locked/unlocked.
		semsg(_(e_lock_unlock), lp->ll_name);
		ret = FAIL;
	    }
	    else
	    {
		if (lock)
		    di->di_flags |= DI_FLAGS_LOCK;
		else
		    di->di_flags &= ~DI_FLAGS_LOCK;
		if (deep != 0)
		    item_lock(&di->di_tv, deep, lock, FALSE);
	    }
	}
	*name_end = cc;
    }
    else if (deep == 0)
    {
	// nothing to do
    }
    else if (lp->ll_range)
    {
	listitem_T    *li = lp->ll_li;

	// (un)lock a range of List items.
	while (li != NULL && (lp->ll_empty2 || lp->ll_n2 >= lp->ll_n1))
	{
	    item_lock(&li->li_tv, deep, lock, FALSE);
	    li = li->li_next;
	    ++lp->ll_n1;
	}
    }
    else if (lp->ll_list != NULL)
	// (un)lock a List item.
	item_lock(&lp->ll_li->li_tv, deep, lock, FALSE);
    else
	// (un)lock a Dictionary item.
	item_lock(&lp->ll_di->di_tv, deep, lock, FALSE);

    return ret;
}

/*
 * Lock or unlock an item.  "deep" is nr of levels to go.
 * When "check_refcount" is TRUE do not lock a list or dict with a reference
 * count larger than 1.
 */
    void
item_lock(typval_T *tv, int deep, int lock, int check_refcount)
{
    static int	recurse = 0;
    list_T	*l;
    listitem_T	*li;
    dict_T	*d;
    blob_T	*b;
    hashitem_T	*hi;
    int		todo;

    if (recurse >= DICT_MAXNEST)
    {
	emsg(_("E743: variable nested too deep for (un)lock"));
	return;
    }
    if (deep == 0)
	return;
    ++recurse;

    // lock/unlock the item itself
    if (lock)
	tv->v_lock |= VAR_LOCKED;
    else
	tv->v_lock &= ~VAR_LOCKED;

    switch (tv->v_type)
    {
	case VAR_UNKNOWN:
	case VAR_ANY:
	case VAR_VOID:
	case VAR_NUMBER:
	case VAR_BOOL:
	case VAR_STRING:
	case VAR_FUNC:
	case VAR_PARTIAL:
	case VAR_FLOAT:
	case VAR_SPECIAL:
	case VAR_JOB:
	case VAR_CHANNEL:
	    break;

	case VAR_BLOB:
	    if ((b = tv->vval.v_blob) != NULL
				    && !(check_refcount && b->bv_refcount > 1))
	    {
		if (lock)
		    b->bv_lock |= VAR_LOCKED;
		else
		    b->bv_lock &= ~VAR_LOCKED;
	    }
	    break;
	case VAR_LIST:
	    if ((l = tv->vval.v_list) != NULL
				    && !(check_refcount && l->lv_refcount > 1))
	    {
		if (lock)
		    l->lv_lock |= VAR_LOCKED;
		else
		    l->lv_lock &= ~VAR_LOCKED;
		if ((deep < 0 || deep > 1) && l->lv_first != &range_list_item)
		    // recursive: lock/unlock the items the List contains
		    FOR_ALL_LIST_ITEMS(l, li)
			item_lock(&li->li_tv, deep - 1, lock, check_refcount);
	    }
	    break;
	case VAR_DICT:
	    if ((d = tv->vval.v_dict) != NULL
				    && !(check_refcount && d->dv_refcount > 1))
	    {
		if (lock)
		    d->dv_lock |= VAR_LOCKED;
		else
		    d->dv_lock &= ~VAR_LOCKED;
		if (deep < 0 || deep > 1)
		{
		    // recursive: lock/unlock the items the List contains
		    todo = (int)d->dv_hashtab.ht_used;
		    for (hi = d->dv_hashtab.ht_array; todo > 0; ++hi)
		    {
			if (!HASHITEM_EMPTY(hi))
			{
			    --todo;
			    item_lock(&HI2DI(hi)->di_tv, deep - 1, lock,
							       check_refcount);
			}
		    }
		}
	    }
    }
    --recurse;
}

#if (defined(FEAT_MENU) && defined(FEAT_MULTI_LANG)) || defined(PROTO)
/*
 * Delete all "menutrans_" variables.
 */
    void
del_menutrans_vars(void)
{
    hashitem_T	*hi;
    int		todo;

    hash_lock(&globvarht);
    todo = (int)globvarht.ht_used;
    for (hi = globvarht.ht_array; todo > 0 && !got_int; ++hi)
    {
	if (!HASHITEM_EMPTY(hi))
	{
	    --todo;
	    if (STRNCMP(HI2DI(hi)->di_key, "menutrans_", 10) == 0)
		delete_var(&globvarht, hi);
	}
    }
    hash_unlock(&globvarht);
}
#endif

/*
 * Local string buffer for the next two functions to store a variable name
 * with its prefix. Allocated in cat_prefix_varname(), freed later in
 * get_user_var_name().
 */

static char_u	*varnamebuf = NULL;
static int	varnamebuflen = 0;

/*
 * Function to concatenate a prefix and a variable name.
 */
    static char_u *
cat_prefix_varname(int prefix, char_u *name)
{
    int		len;

    len = (int)STRLEN(name) + 3;
    if (len > varnamebuflen)
    {
	vim_free(varnamebuf);
	len += 10;			// some additional space
	varnamebuf = alloc(len);
	if (varnamebuf == NULL)
	{
	    varnamebuflen = 0;
	    return NULL;
	}
	varnamebuflen = len;
    }
    *varnamebuf = prefix;
    varnamebuf[1] = ':';
    STRCPY(varnamebuf + 2, name);
    return varnamebuf;
}

/*
 * Function given to ExpandGeneric() to obtain the list of user defined
 * (global/buffer/window/built-in) variable names.
 */
    char_u *
get_user_var_name(expand_T *xp, int idx)
{
    static long_u	gdone;
    static long_u	bdone;
    static long_u	wdone;
    static long_u	tdone;
    static int		vidx;
    static hashitem_T	*hi;
    hashtab_T		*ht;

    if (idx == 0)
    {
	gdone = bdone = wdone = vidx = 0;
	tdone = 0;
    }

    // Global variables
    if (gdone < globvarht.ht_used)
    {
	if (gdone++ == 0)
	    hi = globvarht.ht_array;
	else
	    ++hi;
	while (HASHITEM_EMPTY(hi))
	    ++hi;
	if (STRNCMP("g:", xp->xp_pattern, 2) == 0)
	    return cat_prefix_varname('g', hi->hi_key);
	return hi->hi_key;
    }

    // b: variables
    ht = &curbuf->b_vars->dv_hashtab;
    if (bdone < ht->ht_used)
    {
	if (bdone++ == 0)
	    hi = ht->ht_array;
	else
	    ++hi;
	while (HASHITEM_EMPTY(hi))
	    ++hi;
	return cat_prefix_varname('b', hi->hi_key);
    }

    // w: variables
    ht = &curwin->w_vars->dv_hashtab;
    if (wdone < ht->ht_used)
    {
	if (wdone++ == 0)
	    hi = ht->ht_array;
	else
	    ++hi;
	while (HASHITEM_EMPTY(hi))
	    ++hi;
	return cat_prefix_varname('w', hi->hi_key);
    }

    // t: variables
    ht = &curtab->tp_vars->dv_hashtab;
    if (tdone < ht->ht_used)
    {
	if (tdone++ == 0)
	    hi = ht->ht_array;
	else
	    ++hi;
	while (HASHITEM_EMPTY(hi))
	    ++hi;
	return cat_prefix_varname('t', hi->hi_key);
    }

    // v: variables
    if (vidx < VV_LEN)
	return cat_prefix_varname('v', (char_u *)vimvars[vidx++].vv_name);

    VIM_CLEAR(varnamebuf);
    varnamebuflen = 0;
    return NULL;
}

    char *
get_var_special_name(int nr)
{
    switch (nr)
    {
	case VVAL_FALSE: return "v:false";
	case VVAL_TRUE:  return "v:true";
	case VVAL_NONE:  return "v:none";
	case VVAL_NULL:  return "v:null";
    }
    internal_error("get_var_special_name()");
    return "42";
}

/*
 * Returns the global variable dictionary
 */
    dict_T *
get_globvar_dict(void)
{
    return &globvardict;
}

/*
 * Returns the global variable hash table
 */
    hashtab_T *
get_globvar_ht(void)
{
    return &globvarht;
}

/*
 * Returns the v: variable dictionary
 */
    dict_T *
get_vimvar_dict(void)
{
    return &vimvardict;
}

/*
 * Returns the index of a v:variable.  Negative if not found.
 * Returns DI_ flags in "di_flags".
 */
    int
find_vim_var(char_u *name, int *di_flags)
{
    dictitem_T	    *di = find_var_in_ht(&vimvarht, 0, name, TRUE);
    struct vimvar   *vv;

    if (di == NULL)
	return -1;
    *di_flags = di->di_flags;
    vv = (struct vimvar *)((char *)di - offsetof(vimvar_T, vv_di));
    return (int)(vv - vimvars);
}


/*
 * Set type of v: variable to "type".
 */
    void
set_vim_var_type(int idx, vartype_T type)
{
    vimvars[idx].vv_type = type;
}

/*
 * Set number v: variable to "val".
 * Note that this does not set the type, use set_vim_var_type() for that.
 */
    void
set_vim_var_nr(int idx, varnumber_T val)
{
    vimvars[idx].vv_nr = val;
}

    char *
get_vim_var_name(int idx)
{
    return vimvars[idx].vv_name;
}

/*
 * Get typval_T v: variable value.
 */
    typval_T *
get_vim_var_tv(int idx)
{
    return &vimvars[idx].vv_tv;
}

/*
 * Set v: variable to "tv".  Only accepts the same type.
 * Takes over the value of "tv".
 */
    int
set_vim_var_tv(int idx, typval_T *tv)
{
    if (vimvars[idx].vv_type != tv->v_type)
    {
	emsg(_(e_type_mismatch_for_v_variable));
	clear_tv(tv);
	return FAIL;
    }
    // VV_RO is also checked when compiling, but let's check here as well.
    if (vimvars[idx].vv_flags & VV_RO)
    {
	semsg(_(e_readonlyvar), vimvars[idx].vv_name);
	return FAIL;
    }
    if (sandbox && (vimvars[idx].vv_flags & VV_RO_SBX))
    {
	semsg(_(e_readonlysbx), vimvars[idx].vv_name);
	return FAIL;
    }
    clear_tv(&vimvars[idx].vv_di.di_tv);
    vimvars[idx].vv_di.di_tv = *tv;
    return OK;
}

/*
 * Get number v: variable value.
 */
    varnumber_T
get_vim_var_nr(int idx)
{
    return vimvars[idx].vv_nr;
}

/*
 * Get string v: variable value.  Uses a static buffer, can only be used once.
 * If the String variable has never been set, return an empty string.
 * Never returns NULL;
 */
    char_u *
get_vim_var_str(int idx)
{
    return tv_get_string(&vimvars[idx].vv_tv);
}

/*
 * Get List v: variable value.  Caller must take care of reference count when
 * needed.
 */
    list_T *
get_vim_var_list(int idx)
{
    return vimvars[idx].vv_list;
}

/*
 * Get Dict v: variable value.  Caller must take care of reference count when
 * needed.
 */
    dict_T *
get_vim_var_dict(int idx)
{
    return vimvars[idx].vv_dict;
}

/*
 * Set v:char to character "c".
 */
    void
set_vim_var_char(int c)
{
    char_u	buf[MB_MAXBYTES + 1];

    if (has_mbyte)
	buf[(*mb_char2bytes)(c, buf)] = NUL;
    else
    {
	buf[0] = c;
	buf[1] = NUL;
    }
    set_vim_var_string(VV_CHAR, buf, -1);
}

/*
 * Set v:count to "count" and v:count1 to "count1".
 * When "set_prevcount" is TRUE first set v:prevcount from v:count.
 */
    void
set_vcount(
    long	count,
    long	count1,
    int		set_prevcount)
{
    if (set_prevcount)
	vimvars[VV_PREVCOUNT].vv_nr = vimvars[VV_COUNT].vv_nr;
    vimvars[VV_COUNT].vv_nr = count;
    vimvars[VV_COUNT1].vv_nr = count1;
}

/*
 * Save variables that might be changed as a side effect.  Used when executing
 * a timer callback.
 */
    void
save_vimvars(vimvars_save_T *vvsave)
{
    vvsave->vv_prevcount = vimvars[VV_PREVCOUNT].vv_nr;
    vvsave->vv_count = vimvars[VV_COUNT].vv_nr;
    vvsave->vv_count1 = vimvars[VV_COUNT1].vv_nr;
}

/*
 * Restore variables saved by save_vimvars().
 */
    void
restore_vimvars(vimvars_save_T *vvsave)
{
    vimvars[VV_PREVCOUNT].vv_nr = vvsave->vv_prevcount;
    vimvars[VV_COUNT].vv_nr = vvsave->vv_count;
    vimvars[VV_COUNT1].vv_nr = vvsave->vv_count1;
}

/*
 * Set string v: variable to a copy of "val". If 'copy' is FALSE, then set the
 * value.
 */
    void
set_vim_var_string(
    int		idx,
    char_u	*val,
    int		len)	    // length of "val" to use or -1 (whole string)
{
    clear_tv(&vimvars[idx].vv_di.di_tv);
    vimvars[idx].vv_type = VAR_STRING;
    if (val == NULL)
	vimvars[idx].vv_str = NULL;
    else if (len == -1)
	vimvars[idx].vv_str = vim_strsave(val);
    else
	vimvars[idx].vv_str = vim_strnsave(val, len);
}

/*
 * Set List v: variable to "val".
 */
    void
set_vim_var_list(int idx, list_T *val)
{
    clear_tv(&vimvars[idx].vv_di.di_tv);
    vimvars[idx].vv_type = VAR_LIST;
    vimvars[idx].vv_list = val;
    if (val != NULL)
	++val->lv_refcount;
}

/*
 * Set Dictionary v: variable to "val".
 */
    void
set_vim_var_dict(int idx, dict_T *val)
{
    clear_tv(&vimvars[idx].vv_di.di_tv);
    vimvars[idx].vv_type = VAR_DICT;
    vimvars[idx].vv_dict = val;
    if (val != NULL)
    {
	++val->dv_refcount;
	dict_set_items_ro(val);
    }
}

/*
 * Set the v:argv list.
 */
    void
set_argv_var(char **argv, int argc)
{
    list_T	*l = list_alloc();
    int		i;

    if (l == NULL)
	getout(1);
    l->lv_lock = VAR_FIXED;
    for (i = 0; i < argc; ++i)
    {
	if (list_append_string(l, (char_u *)argv[i], -1) == FAIL)
	    getout(1);
	l->lv_u.mat.lv_last->li_tv.v_lock = VAR_FIXED;
    }
    set_vim_var_list(VV_ARGV, l);
}

/*
 * Reset v:register, taking the 'clipboard' setting into account.
 */
    void
reset_reg_var(void)
{
    int regname = 0;

    // Adjust the register according to 'clipboard', so that when
    // "unnamed" is present it becomes '*' or '+' instead of '"'.
#ifdef FEAT_CLIPBOARD
    adjust_clip_reg(&regname);
#endif
    set_reg_var(regname);
}

/*
 * Set v:register if needed.
 */
    void
set_reg_var(int c)
{
    char_u	regname;

    if (c == 0 || c == ' ')
	regname = '"';
    else
	regname = c;
    // Avoid free/alloc when the value is already right.
    if (vimvars[VV_REG].vv_str == NULL || vimvars[VV_REG].vv_str[0] != c)
	set_vim_var_string(VV_REG, &regname, 1);
}

/*
 * Get or set v:exception.  If "oldval" == NULL, return the current value.
 * Otherwise, restore the value to "oldval" and return NULL.
 * Must always be called in pairs to save and restore v:exception!  Does not
 * take care of memory allocations.
 */
    char_u *
v_exception(char_u *oldval)
{
    if (oldval == NULL)
	return vimvars[VV_EXCEPTION].vv_str;

    vimvars[VV_EXCEPTION].vv_str = oldval;
    return NULL;
}

/*
 * Get or set v:throwpoint.  If "oldval" == NULL, return the current value.
 * Otherwise, restore the value to "oldval" and return NULL.
 * Must always be called in pairs to save and restore v:throwpoint!  Does not
 * take care of memory allocations.
 */
    char_u *
v_throwpoint(char_u *oldval)
{
    if (oldval == NULL)
	return vimvars[VV_THROWPOINT].vv_str;

    vimvars[VV_THROWPOINT].vv_str = oldval;
    return NULL;
}

/*
 * Set v:cmdarg.
 * If "eap" != NULL, use "eap" to generate the value and return the old value.
 * If "oldarg" != NULL, restore the value to "oldarg" and return NULL.
 * Must always be called in pairs!
 */
    char_u *
set_cmdarg(exarg_T *eap, char_u *oldarg)
{
    char_u	*oldval;
    char_u	*newval;
    unsigned	len;

    oldval = vimvars[VV_CMDARG].vv_str;
    if (eap == NULL)
    {
	vim_free(oldval);
	vimvars[VV_CMDARG].vv_str = oldarg;
	return NULL;
    }

    if (eap->force_bin == FORCE_BIN)
	len = 6;
    else if (eap->force_bin == FORCE_NOBIN)
	len = 8;
    else
	len = 0;

    if (eap->read_edit)
	len += 7;

    if (eap->force_ff != 0)
	len += 10; // " ++ff=unix"
    if (eap->force_enc != 0)
	len += (unsigned)STRLEN(eap->cmd + eap->force_enc) + 7;
    if (eap->bad_char != 0)
	len += 7 + 4;  // " ++bad=" + "keep" or "drop"

    newval = alloc(len + 1);
    if (newval == NULL)
	return NULL;

    if (eap->force_bin == FORCE_BIN)
	sprintf((char *)newval, " ++bin");
    else if (eap->force_bin == FORCE_NOBIN)
	sprintf((char *)newval, " ++nobin");
    else
	*newval = NUL;

    if (eap->read_edit)
	STRCAT(newval, " ++edit");

    if (eap->force_ff != 0)
	sprintf((char *)newval + STRLEN(newval), " ++ff=%s",
						eap->force_ff == 'u' ? "unix"
						: eap->force_ff == 'd' ? "dos"
						: "mac");
    if (eap->force_enc != 0)
	sprintf((char *)newval + STRLEN(newval), " ++enc=%s",
					       eap->cmd + eap->force_enc);
    if (eap->bad_char == BAD_KEEP)
	STRCPY(newval + STRLEN(newval), " ++bad=keep");
    else if (eap->bad_char == BAD_DROP)
	STRCPY(newval + STRLEN(newval), " ++bad=drop");
    else if (eap->bad_char != 0)
	sprintf((char *)newval + STRLEN(newval), " ++bad=%c", eap->bad_char);
    vimvars[VV_CMDARG].vv_str = newval;
    return oldval;
}

/*
 * Get the value of internal variable "name".
 * Return OK or FAIL.  If OK is returned "rettv" must be cleared.
 */
    int
eval_variable(
    char_u	*name,
    int		len,		// length of "name"
    typval_T	*rettv,		// NULL when only checking existence
    dictitem_T	**dip,		// non-NULL when typval's dict item is needed
    int		verbose,	// may give error message
    int		no_autoload)	// do not use script autoloading
{
    int		ret = OK;
    typval_T	*tv = NULL;
    int		foundFunc = FALSE;
    dictitem_T	*v;
    int		cc;

    // truncate the name, so that we can use strcmp()
    cc = name[len];
    name[len] = NUL;

    // Check for user-defined variables.
    v = find_var(name, NULL, no_autoload);
    if (v != NULL)
    {
	tv = &v->di_tv;
	if (dip != NULL)
	    *dip = v;
    }

    if (tv == NULL && (in_vim9script() || STRNCMP(name, "s:", 2) == 0))
    {
	imported_T  *import;
	char_u	    *p = STRNCMP(name, "s:", 2) == 0 ? name + 2 : name;

	import = find_imported(p, 0, NULL);

	// imported variable from another script
	if (import != NULL)
	{
	    if (import->imp_funcname != NULL)
	    {
		foundFunc = TRUE;
		if (rettv != NULL)
		{
		    rettv->v_type = VAR_FUNC;
		    rettv->vval.v_string = vim_strsave(import->imp_funcname);
		}
	    }
	    else if (import->imp_all)
	    {
		emsg("Sorry, 'import * as X' not implemented yet");
		ret = FAIL;
	    }
	    else
	    {
		scriptitem_T    *si = SCRIPT_ITEM(import->imp_sid);
		svar_T		*sv = ((svar_T *)si->sn_var_vals.ga_data)
						    + import->imp_var_vals_idx;
		tv = sv->sv_tv;
	    }
	}
	else if (in_vim9script())
	{
	    ufunc_T *ufunc = find_func(name, FALSE, NULL);

	    if (ufunc != NULL)
	    {
		foundFunc = TRUE;
		if (rettv != NULL)
		{
		    rettv->v_type = VAR_FUNC;
		    rettv->vval.v_string = vim_strsave(ufunc->uf_name);
		}
	    }
	}
    }

    if (!foundFunc)
    {
	if (tv == NULL)
	{
	    if (rettv != NULL && verbose)
		semsg(_(e_undefined_variable_str), name);
	    ret = FAIL;
	}
	else if (rettv != NULL)
	    copy_tv(tv, rettv);
    }

    name[len] = cc;

    return ret;
}

/*
 * Check if variable "name[len]" is a local variable or an argument.
 * If so, "*eval_lavars_used" is set to TRUE.
 */
    void
check_vars(char_u *name, int len)
{
    int		cc;
    char_u	*varname;
    hashtab_T	*ht;

    if (eval_lavars_used == NULL)
	return;

    // truncate the name, so that we can use strcmp()
    cc = name[len];
    name[len] = NUL;

    ht = find_var_ht(name, &varname);
    if (ht == get_funccal_local_ht() || ht == get_funccal_args_ht())
    {
	if (find_var(name, NULL, TRUE) != NULL)
	    *eval_lavars_used = TRUE;
    }

    name[len] = cc;
}

/*
 * Find variable "name" in the list of variables.
 * Return a pointer to it if found, NULL if not found.
 * Careful: "a:0" variables don't have a name.
 * When "htp" is not NULL we are writing to the variable, set "htp" to the
 * hashtab_T used.
 */
    dictitem_T *
find_var(char_u *name, hashtab_T **htp, int no_autoload)
{
    char_u	*varname;
    hashtab_T	*ht;
    dictitem_T	*ret = NULL;

    ht = find_var_ht(name, &varname);
    if (htp != NULL)
	*htp = ht;
    if (ht == NULL)
	return NULL;
    ret = find_var_in_ht(ht, *name, varname, no_autoload || htp != NULL);
    if (ret != NULL)
	return ret;

    // Search in parent scope for lambda
    return find_var_in_scoped_ht(name, no_autoload || htp != NULL);
}

/*
 * Find variable "varname" in hashtab "ht" with name "htname".
 * When "varname" is empty returns curwin/curtab/etc vars dictionary.
 * Returns NULL if not found.
 */
    dictitem_T *
find_var_in_ht(
    hashtab_T	*ht,
    int		htname,
    char_u	*varname,
    int		no_autoload)
{
    hashitem_T	*hi;

    if (*varname == NUL)
    {
	// Must be something like "s:", otherwise "ht" would be NULL.
	switch (htname)
	{
	    case 's': return &SCRIPT_SV(current_sctx.sc_sid)->sv_var;
	    case 'g': return &globvars_var;
	    case 'v': return &vimvars_var;
	    case 'b': return &curbuf->b_bufvar;
	    case 'w': return &curwin->w_winvar;
	    case 't': return &curtab->tp_winvar;
	    case 'l': return get_funccal_local_var();
	    case 'a': return get_funccal_args_var();
	}
	return NULL;
    }

    hi = hash_find(ht, varname);
    if (HASHITEM_EMPTY(hi))
    {
	// For global variables we may try auto-loading the script.  If it
	// worked find the variable again.  Don't auto-load a script if it was
	// loaded already, otherwise it would be loaded every time when
	// checking if a function name is a Funcref variable.
	if (ht == &globvarht && !no_autoload)
	{
	    // Note: script_autoload() may make "hi" invalid. It must either
	    // be obtained again or not used.
	    if (!script_autoload(varname, FALSE) || aborting())
		return NULL;
	    hi = hash_find(ht, varname);
	}
	if (HASHITEM_EMPTY(hi))
	    return NULL;
    }
    return HI2DI(hi);
}

/*
 * Get the script-local hashtab.  NULL if not in a script context.
 */
    hashtab_T *
get_script_local_ht(void)
{
    scid_T sid = current_sctx.sc_sid;

    if (SCRIPT_ID_VALID(sid))
	return &SCRIPT_VARS(sid);
    return NULL;
}

/*
 * Look for "name[len]" in script-local variables.
 * Return a non-NULL pointer when found, NULL when not found.
 */
    void *
lookup_scriptvar(char_u *name, size_t len, cctx_T *dummy UNUSED)
{
    hashtab_T	*ht = get_script_local_ht();
    char_u	buffer[30];
    char_u	*p;
    void	*res;
    hashitem_T	*hi;

    if (ht == NULL)
	return NULL;
    if (len < sizeof(buffer) - 1)
    {
	// avoid an alloc/free for short names
	vim_strncpy(buffer, name, len);
	p = buffer;
    }
    else
    {
	p = vim_strnsave(name, len);
	if (p == NULL)
	    return NULL;
    }

    hi = hash_find(ht, p);
    res = HASHITEM_EMPTY(hi) ? NULL : hi;

    // if not script-local, then perhaps imported
    if (res == NULL && find_imported(p, 0, NULL) != NULL)
	res = p;

    if (p != buffer)
	vim_free(p);
    // Don't return "buffer", gcc complains.
    return res == NULL ? NULL : IObuff;
}

/*
 * Find the hashtab used for a variable name.
 * Return NULL if the name is not valid.
 * Set "varname" to the start of name without ':'.
 */
    hashtab_T *
find_var_ht(char_u *name, char_u **varname)
{
    hashitem_T	*hi;
    hashtab_T	*ht;

    if (name[0] == NUL)
	return NULL;
    if (name[1] != ':')
    {
	// The name must not start with a colon or #.
	if (name[0] == ':' || name[0] == AUTOLOAD_CHAR)
	    return NULL;
	*varname = name;

	// "version" is "v:version" in all scopes if scriptversion < 3.
	// Same for a few other variables marked with VV_COMPAT.
	if (current_sctx.sc_version < 3)
	{
	    hi = hash_find(&compat_hashtab, name);
	    if (!HASHITEM_EMPTY(hi))
		return &compat_hashtab;
	}

	ht = get_funccal_local_ht();
	if (ht != NULL)
	    return ht;				// local variable

	// in Vim9 script items at the script level are script-local
	if (in_vim9script())
	{
	    ht = get_script_local_ht();
	    if (ht != NULL)
		return ht;
	}

	return &globvarht;			// global variable
    }
    *varname = name + 2;
    if (*name == 'g')				// global variable
	return &globvarht;
    // There must be no ':' or '#' in the rest of the name, unless g: is used
    if (vim_strchr(name + 2, ':') != NULL
			       || vim_strchr(name + 2, AUTOLOAD_CHAR) != NULL)
	return NULL;
    if (*name == 'b')				// buffer variable
	return &curbuf->b_vars->dv_hashtab;
    if (*name == 'w')				// window variable
	return &curwin->w_vars->dv_hashtab;
    if (*name == 't')				// tab page variable
	return &curtab->tp_vars->dv_hashtab;
    if (*name == 'v')				// v: variable
	return &vimvarht;
    if (get_current_funccal() != NULL
	       && get_current_funccal()->func->uf_def_status == UF_NOT_COMPILED)
    {
	// a: and l: are only used in functions defined with ":function"
	if (*name == 'a')			// a: function argument
	    return get_funccal_args_ht();
	if (*name == 'l')			// l: local function variable
	    return get_funccal_local_ht();
    }
    if (*name == 's')				// script variable
    {
	ht = get_script_local_ht();
	if (ht != NULL)
	    return ht;
    }
    return NULL;
}

/*
 * Get the string value of a (global/local) variable.
 * Note: see tv_get_string() for how long the pointer remains valid.
 * Returns NULL when it doesn't exist.
 */
    char_u *
get_var_value(char_u *name)
{
    dictitem_T	*v;

    v = find_var(name, NULL, FALSE);
    if (v == NULL)
	return NULL;
    return tv_get_string(&v->di_tv);
}

/*
 * Allocate a new hashtab for a sourced script.  It will be used while
 * sourcing this script and when executing functions defined in the script.
 */
    void
new_script_vars(scid_T id)
{
    scriptvar_T *sv;

    sv = ALLOC_CLEAR_ONE(scriptvar_T);
    if (sv == NULL)
	return;
    init_var_dict(&sv->sv_dict, &sv->sv_var, VAR_SCOPE);
    SCRIPT_ITEM(id)->sn_vars = sv;
}

/*
 * Initialize dictionary "dict" as a scope and set variable "dict_var" to
 * point to it.
 */
    void
init_var_dict(dict_T *dict, dictitem_T *dict_var, int scope)
{
    hash_init(&dict->dv_hashtab);
    dict->dv_lock = 0;
    dict->dv_scope = scope;
    dict->dv_refcount = DO_NOT_FREE_CNT;
    dict->dv_copyID = 0;
    dict_var->di_tv.vval.v_dict = dict;
    dict_var->di_tv.v_type = VAR_DICT;
    dict_var->di_tv.v_lock = VAR_FIXED;
    dict_var->di_flags = DI_FLAGS_RO | DI_FLAGS_FIX;
    dict_var->di_key[0] = NUL;
}

/*
 * Unreference a dictionary initialized by init_var_dict().
 */
    void
unref_var_dict(dict_T *dict)
{
    // Now the dict needs to be freed if no one else is using it, go back to
    // normal reference counting.
    dict->dv_refcount -= DO_NOT_FREE_CNT - 1;
    dict_unref(dict);
}

/*
 * Clean up a list of internal variables.
 * Frees all allocated variables and the value they contain.
 * Clears hashtab "ht", does not free it.
 */
    void
vars_clear(hashtab_T *ht)
{
    vars_clear_ext(ht, TRUE);
}

/*
 * Like vars_clear(), but only free the value if "free_val" is TRUE.
 */
    void
vars_clear_ext(hashtab_T *ht, int free_val)
{
    int		todo;
    hashitem_T	*hi;
    dictitem_T	*v;

    hash_lock(ht);
    todo = (int)ht->ht_used;
    for (hi = ht->ht_array; todo > 0; ++hi)
    {
	if (!HASHITEM_EMPTY(hi))
	{
	    --todo;

	    // Free the variable.  Don't remove it from the hashtab,
	    // ht_array might change then.  hash_clear() takes care of it
	    // later.
	    v = HI2DI(hi);
	    if (free_val)
		clear_tv(&v->di_tv);
	    if (v->di_flags & DI_FLAGS_ALLOC)
		vim_free(v);
	}
    }
    hash_clear(ht);
    hash_init(ht);
}

/*
 * Delete a variable from hashtab "ht" at item "hi".
 * Clear the variable value and free the dictitem.
 */
    void
delete_var(hashtab_T *ht, hashitem_T *hi)
{
    dictitem_T	*di = HI2DI(hi);

    hash_remove(ht, hi);
    clear_tv(&di->di_tv);
    vim_free(di);
}

/*
 * List the value of one internal variable.
 */
    static void
list_one_var(dictitem_T *v, char *prefix, int *first)
{
    char_u	*tofree;
    char_u	*s;
    char_u	numbuf[NUMBUFLEN];

    s = echo_string(&v->di_tv, &tofree, numbuf, get_copyID());
    list_one_var_a(prefix, v->di_key, v->di_tv.v_type,
					 s == NULL ? (char_u *)"" : s, first);
    vim_free(tofree);
}

    static void
list_one_var_a(
    char	*prefix,
    char_u	*name,
    int		type,
    char_u	*string,
    int		*first)  // when TRUE clear rest of screen and set to FALSE
{
    // don't use msg() or msg_attr() to avoid overwriting "v:statusmsg"
    msg_start();
    msg_puts(prefix);
    if (name != NULL)	// "a:" vars don't have a name stored
	msg_puts((char *)name);
    msg_putchar(' ');
    msg_advance(22);
    if (type == VAR_NUMBER)
	msg_putchar('#');
    else if (type == VAR_FUNC || type == VAR_PARTIAL)
	msg_putchar('*');
    else if (type == VAR_LIST)
    {
	msg_putchar('[');
	if (*string == '[')
	    ++string;
    }
    else if (type == VAR_DICT)
    {
	msg_putchar('{');
	if (*string == '{')
	    ++string;
    }
    else
	msg_putchar(' ');

    msg_outtrans(string);

    if (type == VAR_FUNC || type == VAR_PARTIAL)
	msg_puts("()");
    if (*first)
    {
	msg_clr_eos();
	*first = FALSE;
    }
}

/*
 * Set variable "name" to value in "tv".
 * If the variable already exists, the value is updated.
 * Otherwise the variable is created.
 */
    void
set_var(
    char_u	*name,
    typval_T	*tv,
    int		copy)	    // make copy of value in "tv"
{
    set_var_const(name, NULL, tv, copy, ASSIGN_NO_DECL);
}

/*
 * Set variable "name" to value in "tv".
 * If the variable already exists and "is_const" is FALSE the value is updated.
 * Otherwise the variable is created.
 */
    void
set_var_const(
    char_u	*name,
    type_T	*type,
    typval_T	*tv_arg,
    int		copy,	    // make copy of value in "tv"
    int		flags)	    // ASSIGN_CONST, ASSIGN_NO_DECL
{
    typval_T	*tv = tv_arg;
    typval_T	bool_tv;
    dictitem_T	*di;
    char_u	*varname;
    hashtab_T	*ht;
    int		is_script_local;
    int		vim9script = in_vim9script();

    ht = find_var_ht(name, &varname);
    if (ht == NULL || *varname == NUL)
    {
	semsg(_(e_illvar), name);
	goto failed;
    }
    is_script_local = ht == get_script_local_ht();

    if (vim9script
	    && !is_script_local
	    && (flags & ASSIGN_NO_DECL) == 0
	    && name[1] == ':')
    {
	vim9_declare_error(name);
	goto failed;
    }

    di = find_var_in_ht(ht, 0, varname, TRUE);

    // Search in parent scope which is possible to reference from lambda
    if (di == NULL)
	di = find_var_in_scoped_ht(name, TRUE);

    if ((tv->v_type == VAR_FUNC || tv->v_type == VAR_PARTIAL)
				      && var_wrong_func_name(name, di == NULL))
	goto failed;

    if (need_convert_to_bool(type, tv))
    {
	// Destination is a bool and the value is not, but it can be converted.
	CLEAR_FIELD(bool_tv);
	bool_tv.v_type = VAR_BOOL;
	bool_tv.vval.v_number = tv2bool(tv) ? VVAL_TRUE : VVAL_FALSE;
	tv = &bool_tv;
    }

    if (di != NULL)
    {
	if ((di->di_flags & DI_FLAGS_RELOAD) == 0)
	{
	    if (flags & ASSIGN_CONST)
	    {
		emsg(_(e_cannot_mod));
		goto failed;
	    }

	    if (is_script_local && vim9script)
	    {
		if ((flags & ASSIGN_NO_DECL) == 0)
		{
		    semsg(_(e_redefining_script_item_str), name);
		    goto failed;
		}

		// check the type and adjust to bool if needed
		if (check_script_var_type(&di->di_tv, tv, name) == FAIL)
		    goto failed;
	    }

	    // Check in this order for backwards compatibility:
	    // - Whether the variable is read-only
	    // - Whether the variable value is locked
	    // - Whether the variable is locked
	    if (var_check_ro(di->di_flags, name, FALSE)
			    || value_check_lock(di->di_tv.v_lock, name, FALSE)
			    || var_check_lock(di->di_flags, name, FALSE))
		goto failed;
	}
	else
	    // can only redefine once
	    di->di_flags &= ~DI_FLAGS_RELOAD;

	// existing variable, need to clear the value

	// Handle setting internal di: variables separately where needed to
	// prevent changing the type.
	if (ht == &vimvarht)
	{
	    if (di->di_tv.v_type == VAR_STRING)
	    {
		VIM_CLEAR(di->di_tv.vval.v_string);
		if (copy || tv->v_type != VAR_STRING)
		{
		    char_u *val = tv_get_string(tv);

		    // Careful: when assigning to v:errmsg and tv_get_string()
		    // causes an error message the variable will already be set.
		    if (di->di_tv.vval.v_string == NULL)
			di->di_tv.vval.v_string = vim_strsave(val);
		}
		else
		{
		    // Take over the string to avoid an extra alloc/free.
		    di->di_tv.vval.v_string = tv->vval.v_string;
		    tv->vval.v_string = NULL;
		}
		goto failed;
	    }
	    else if (di->di_tv.v_type == VAR_NUMBER)
	    {
		di->di_tv.vval.v_number = tv_get_number(tv);
		if (STRCMP(varname, "searchforward") == 0)
		    set_search_direction(di->di_tv.vval.v_number ? '/' : '?');
#ifdef FEAT_SEARCH_EXTRA
		else if (STRCMP(varname, "hlsearch") == 0)
		{
		    no_hlsearch = !di->di_tv.vval.v_number;
		    redraw_all_later(SOME_VALID);
		}
#endif
		goto failed;
	    }
	    else if (di->di_tv.v_type != tv->v_type)
	    {
		semsg(_("E963: setting %s to value with wrong type"), name);
		goto failed;
	    }
	}

	clear_tv(&di->di_tv);
    }
    else		    // add a new variable
    {
	// Can't add "v:" or "a:" variable.
	if (ht == &vimvarht || ht == get_funccal_args_ht())
	{
	    semsg(_(e_illvar), name);
	    goto failed;
	}

	// Make sure the variable name is valid.
	if (!valid_varname(varname))
	    goto failed;

	di = alloc(sizeof(dictitem_T) + STRLEN(varname));
	if (di == NULL)
	    goto failed;
	STRCPY(di->di_key, varname);
	if (hash_add(ht, DI2HIKEY(di)) == FAIL)
	{
	    vim_free(di);
	    goto failed;
	}
	di->di_flags = DI_FLAGS_ALLOC;
	if (flags & ASSIGN_CONST)
	    di->di_flags |= DI_FLAGS_LOCK;

	// A Vim9 script-local variable is also added to sn_all_vars and
	// sn_var_vals.
	if (is_script_local && vim9script)
	    add_vim9_script_var(di, tv, type);
    }

    if (copy || tv->v_type == VAR_NUMBER || tv->v_type == VAR_FLOAT)
	copy_tv(tv, &di->di_tv);
    else
    {
	di->di_tv = *tv;
	di->di_tv.v_lock = 0;
	init_tv(tv);
    }

    // ":const var = val" locks the value
    if (flags & ASSIGN_CONST)
	// Like :lockvar! name: lock the value and what it contains, but only
	// if the reference count is up to one.  That locks only literal
	// values.
	item_lock(&di->di_tv, DICT_MAXNEST, TRUE, TRUE);
    return;
failed:
    if (!copy)
	clear_tv(tv_arg);
}

/*
 * Return TRUE if di_flags "flags" indicates variable "name" is read-only.
 * Also give an error message.
 */
    int
var_check_ro(int flags, char_u *name, int use_gettext)
{
    if (flags & DI_FLAGS_RO)
    {
	semsg(_(e_readonlyvar), use_gettext ? (char_u *)_(name) : name);
	return TRUE;
    }
    if ((flags & DI_FLAGS_RO_SBX) && sandbox)
    {
	semsg(_(e_readonlysbx), use_gettext ? (char_u *)_(name) : name);
	return TRUE;
    }
    return FALSE;
}

/*
 * Return TRUE if di_flags "flags" indicates variable "name" is locked.
 * Also give an error message.
 */
    int
var_check_lock(int flags, char_u *name, int use_gettext)
{
    if (flags & DI_FLAGS_LOCK)
    {
	semsg(_(e_variable_is_locked_str),
				       use_gettext ? (char_u *)_(name) : name);
	return TRUE;
    }
    return FALSE;
}

/*
 * Return TRUE if di_flags "flags" indicates variable "name" is fixed.
 * Also give an error message.
 */
    int
var_check_fixed(int flags, char_u *name, int use_gettext)
{
    if (flags & DI_FLAGS_FIX)
    {
	semsg(_("E795: Cannot delete variable %s"),
				      use_gettext ? (char_u *)_(name) : name);
	return TRUE;
    }
    return FALSE;
}

/*
 * Check if a funcref is assigned to a valid variable name.
 * Return TRUE and give an error if not.
 */
    int
var_wrong_func_name(
    char_u *name,    // points to start of variable name
    int    new_var)  // TRUE when creating the variable
{
    // Allow for w: b: s: and t:.
    if (!(vim_strchr((char_u *)"wbst", name[0]) != NULL && name[1] == ':')
	    && !ASCII_ISUPPER((name[0] != NUL && name[1] == ':')
						     ? name[2] : name[0]))
    {
	semsg(_("E704: Funcref variable name must start with a capital: %s"),
									name);
	return TRUE;
    }
    // Don't allow hiding a function.  When "v" is not NULL we might be
    // assigning another function to the same var, the type is checked
    // below.
    if (new_var && function_exists(name, FALSE))
    {
	semsg(_("E705: Variable name conflicts with existing function: %s"),
								    name);
	return TRUE;
    }
    return FALSE;
}

/*
 * Return TRUE if "flags" indicates variable "name" has a locked (immutable)
 * value.  Also give an error message, using "name" or _("name") when
 * "use_gettext" is TRUE.
 */
    int
value_check_lock(int lock, char_u *name, int use_gettext)
{
    if (lock & VAR_LOCKED)
    {
	semsg(_("E741: Value is locked: %s"),
				name == NULL ? (char_u *)_("Unknown")
					     : use_gettext ? (char_u *)_(name)
					     : name);
	return TRUE;
    }
    if (lock & VAR_FIXED)
    {
	semsg(_("E742: Cannot change value of %s"),
				name == NULL ? (char_u *)_("Unknown")
					     : use_gettext ? (char_u *)_(name)
					     : name);
	return TRUE;
    }
    return FALSE;
}

/*
 * Check if a variable name is valid.
 * Return FALSE and give an error if not.
 */
    int
valid_varname(char_u *varname)
{
    char_u *p;

    for (p = varname; *p != NUL; ++p)
	if (!eval_isnamec1(*p) && (p == varname || !VIM_ISDIGIT(*p))
						   && *p != AUTOLOAD_CHAR)
	{
	    semsg(_(e_illvar), varname);
	    return FALSE;
	}
    return TRUE;
}

/*
 * getwinvar() and gettabwinvar()
 */
    static void
getwinvar(
    typval_T	*argvars,
    typval_T	*rettv,
    int		off)	    // 1 for gettabwinvar()
{
    win_T	*win;
    char_u	*varname;
    dictitem_T	*v;
    tabpage_T	*tp = NULL;
    int		done = FALSE;
    win_T	*oldcurwin;
    tabpage_T	*oldtabpage;
    int		need_switch_win;

    if (off == 1)
	tp = find_tabpage((int)tv_get_number_chk(&argvars[0], NULL));
    else
	tp = curtab;
    win = find_win_by_nr(&argvars[off], tp);
    varname = tv_get_string_chk(&argvars[off + 1]);
    ++emsg_off;

    rettv->v_type = VAR_STRING;
    rettv->vval.v_string = NULL;

    if (win != NULL && varname != NULL)
    {
	// Set curwin to be our win, temporarily.  Also set the tabpage,
	// otherwise the window is not valid. Only do this when needed,
	// autocommands get blocked.
	need_switch_win = !(tp == curtab && win == curwin);
	if (!need_switch_win
		  || switch_win(&oldcurwin, &oldtabpage, win, tp, TRUE) == OK)
	{
	    if (*varname == '&')
	    {
		if (varname[1] == NUL)
		{
		    // get all window-local options in a dict
		    dict_T	*opts = get_winbuf_options(FALSE);

		    if (opts != NULL)
		    {
			rettv_dict_set(rettv, opts);
			done = TRUE;
		    }
		}
		else if (eval_option(&varname, rettv, 1) == OK)
		    // window-local-option
		    done = TRUE;
	    }
	    else
	    {
		// Look up the variable.
		// Let getwinvar({nr}, "") return the "w:" dictionary.
		v = find_var_in_ht(&win->w_vars->dv_hashtab, 'w',
							      varname, FALSE);
		if (v != NULL)
		{
		    copy_tv(&v->di_tv, rettv);
		    done = TRUE;
		}
	    }
	}

	if (need_switch_win)
	    // restore previous notion of curwin
	    restore_win(oldcurwin, oldtabpage, TRUE);
    }

    if (!done && argvars[off + 2].v_type != VAR_UNKNOWN)
	// use the default return value
	copy_tv(&argvars[off + 2], rettv);

    --emsg_off;
}

/*
 * Set option "varname" to the value of "varp" for the current buffer/window.
 */
    static void
set_option_from_tv(char_u *varname, typval_T *varp)
{
    long	numval = 0;
    char_u	*strval;
    char_u	nbuf[NUMBUFLEN];
    int		error = FALSE;

    if (!in_vim9script() || varp->v_type != VAR_STRING)
	numval = (long)tv_get_number_chk(varp, &error);
    strval = tv_get_string_buf_chk(varp, nbuf);
    if (!error && strval != NULL)
	set_option_value(varname, numval, strval, OPT_LOCAL);
}

/*
 * "setwinvar()" and "settabwinvar()" functions
 */
    static void
setwinvar(typval_T *argvars, int off)
{
    win_T	*win;
    win_T	*save_curwin;
    tabpage_T	*save_curtab;
    int		need_switch_win;
    char_u	*varname, *winvarname;
    typval_T	*varp;
    tabpage_T	*tp = NULL;

    if (check_secure())
	return;

    if (off == 1)
	tp = find_tabpage((int)tv_get_number_chk(&argvars[0], NULL));
    else
	tp = curtab;
    win = find_win_by_nr(&argvars[off], tp);
    varname = tv_get_string_chk(&argvars[off + 1]);
    varp = &argvars[off + 2];

    if (win != NULL && varname != NULL && varp != NULL)
    {
	need_switch_win = !(tp == curtab && win == curwin);
	if (!need_switch_win
	       || switch_win(&save_curwin, &save_curtab, win, tp, TRUE) == OK)
	{
	    if (*varname == '&')
		set_option_from_tv(varname + 1, varp);
	    else
	    {
		winvarname = alloc(STRLEN(varname) + 3);
		if (winvarname != NULL)
		{
		    STRCPY(winvarname, "w:");
		    STRCPY(winvarname + 2, varname);
		    set_var(winvarname, varp, TRUE);
		    vim_free(winvarname);
		}
	    }
	}
	if (need_switch_win)
	    restore_win(save_curwin, save_curtab, TRUE);
    }
}

/*
 * reset v:option_new, v:option_old, v:option_oldlocal, v:option_oldglobal,
 * v:option_type, and v:option_command.
 */
    void
reset_v_option_vars(void)
{
    set_vim_var_string(VV_OPTION_NEW,  NULL, -1);
    set_vim_var_string(VV_OPTION_OLD,  NULL, -1);
    set_vim_var_string(VV_OPTION_OLDLOCAL, NULL, -1);
    set_vim_var_string(VV_OPTION_OLDGLOBAL, NULL, -1);
    set_vim_var_string(VV_OPTION_TYPE, NULL, -1);
    set_vim_var_string(VV_OPTION_COMMAND, NULL, -1);
}

/*
 * Add an assert error to v:errors.
 */
    void
assert_error(garray_T *gap)
{
    struct vimvar   *vp = &vimvars[VV_ERRORS];

    if (vp->vv_type != VAR_LIST || vimvars[VV_ERRORS].vv_list == NULL)
	// Make sure v:errors is a list.
	set_vim_var_list(VV_ERRORS, list_alloc());
    list_append_string(vimvars[VV_ERRORS].vv_list, gap->ga_data, gap->ga_len);
}

    int
var_exists(char_u *var)
{
    char_u	*arg = var;
    char_u	*name;
    char_u	*tofree;
    typval_T    tv;
    int		len = 0;
    int		n = FALSE;

    // get_name_len() takes care of expanding curly braces
    name = var;
    len = get_name_len(&arg, &tofree, TRUE, FALSE);
    if (len > 0)
    {
	if (tofree != NULL)
	    name = tofree;
	n = (eval_variable(name, len, &tv, NULL, FALSE, TRUE) == OK);
	if (n)
	{
	    // handle d.key, l[idx], f(expr)
	    arg = skipwhite(arg);
	    n = (handle_subscript(&arg, &tv, &EVALARG_EVALUATE, FALSE) == OK);
	    if (n)
		clear_tv(&tv);
	}
    }
    if (*arg != NUL)
	n = FALSE;

    vim_free(tofree);
    return n;
}

static lval_T	*redir_lval = NULL;
#define EVALCMD_BUSY (redir_lval == (lval_T *)&redir_lval)
static garray_T redir_ga;	// only valid when redir_lval is not NULL
static char_u	*redir_endp = NULL;
static char_u	*redir_varname = NULL;

/*
 * Start recording command output to a variable
 * When "append" is TRUE append to an existing variable.
 * Returns OK if successfully completed the setup.  FAIL otherwise.
 */
    int
var_redir_start(char_u *name, int append)
{
    int		called_emsg_before;
    typval_T	tv;

    // Catch a bad name early.
    if (!eval_isnamec1(*name))
    {
	emsg(_(e_invarg));
	return FAIL;
    }

    // Make a copy of the name, it is used in redir_lval until redir ends.
    redir_varname = vim_strsave(name);
    if (redir_varname == NULL)
	return FAIL;

    redir_lval = ALLOC_CLEAR_ONE(lval_T);
    if (redir_lval == NULL)
    {
	var_redir_stop();
	return FAIL;
    }

    // The output is stored in growarray "redir_ga" until redirection ends.
    ga_init2(&redir_ga, (int)sizeof(char), 500);

    // Parse the variable name (can be a dict or list entry).
    redir_endp = get_lval(redir_varname, NULL, redir_lval, FALSE, FALSE, 0,
							     FNE_CHECK_START);
    if (redir_endp == NULL || redir_lval->ll_name == NULL || *redir_endp != NUL)
    {
	clear_lval(redir_lval);
	if (redir_endp != NULL && *redir_endp != NUL)
	    // Trailing characters are present after the variable name
	    semsg(_(e_trailing_arg), redir_endp);
	else
	    semsg(_(e_invarg2), name);
	redir_endp = NULL;  // don't store a value, only cleanup
	var_redir_stop();
	return FAIL;
    }

    // check if we can write to the variable: set it to or append an empty
    // string
    called_emsg_before = called_emsg;
    tv.v_type = VAR_STRING;
    tv.vval.v_string = (char_u *)"";
    if (append)
	set_var_lval(redir_lval, redir_endp, &tv, TRUE, 0, (char_u *)".");
    else
	set_var_lval(redir_lval, redir_endp, &tv, TRUE, 0, (char_u *)"=");
    clear_lval(redir_lval);
    if (called_emsg > called_emsg_before)
    {
	redir_endp = NULL;  // don't store a value, only cleanup
	var_redir_stop();
	return FAIL;
    }

    return OK;
}

/*
 * Append "value[value_len]" to the variable set by var_redir_start().
 * The actual appending is postponed until redirection ends, because the value
 * appended may in fact be the string we write to, changing it may cause freed
 * memory to be used:
 *   :redir => foo
 *   :let foo
 *   :redir END
 */
    void
var_redir_str(char_u *value, int value_len)
{
    int		len;

    if (redir_lval == NULL)
	return;

    if (value_len == -1)
	len = (int)STRLEN(value);	// Append the entire string
    else
	len = value_len;		// Append only "value_len" characters

    if (ga_grow(&redir_ga, len) == OK)
    {
	mch_memmove((char *)redir_ga.ga_data + redir_ga.ga_len, value, len);
	redir_ga.ga_len += len;
    }
    else
	var_redir_stop();
}

/*
 * Stop redirecting command output to a variable.
 * Frees the allocated memory.
 */
    void
var_redir_stop(void)
{
    typval_T	tv;

    if (EVALCMD_BUSY)
    {
	redir_lval = NULL;
	return;
    }

    if (redir_lval != NULL)
    {
	// If there was no error: assign the text to the variable.
	if (redir_endp != NULL)
	{
	    ga_append(&redir_ga, NUL);  // Append the trailing NUL.
	    tv.v_type = VAR_STRING;
	    tv.vval.v_string = redir_ga.ga_data;
	    // Call get_lval() again, if it's inside a Dict or List it may
	    // have changed.
	    redir_endp = get_lval(redir_varname, NULL, redir_lval,
					FALSE, FALSE, 0, FNE_CHECK_START);
	    if (redir_endp != NULL && redir_lval->ll_name != NULL)
		set_var_lval(redir_lval, redir_endp, &tv, FALSE, 0,
								(char_u *)".");
	    clear_lval(redir_lval);
	}

	// free the collected output
	VIM_CLEAR(redir_ga.ga_data);

	VIM_CLEAR(redir_lval);
    }
    VIM_CLEAR(redir_varname);
}

/*
 * "gettabvar()" function
 */
    void
f_gettabvar(typval_T *argvars, typval_T *rettv)
{
    win_T	*oldcurwin;
    tabpage_T	*tp, *oldtabpage;
    dictitem_T	*v;
    char_u	*varname;
    int		done = FALSE;

    rettv->v_type = VAR_STRING;
    rettv->vval.v_string = NULL;

    varname = tv_get_string_chk(&argvars[1]);
    tp = find_tabpage((int)tv_get_number_chk(&argvars[0], NULL));
    if (tp != NULL && varname != NULL)
    {
	// Set tp to be our tabpage, temporarily.  Also set the window to the
	// first window in the tabpage, otherwise the window is not valid.
	if (switch_win(&oldcurwin, &oldtabpage,
		tp == curtab || tp->tp_firstwin == NULL ? firstwin
					    : tp->tp_firstwin, tp, TRUE) == OK)
	{
	    // look up the variable
	    // Let gettabvar({nr}, "") return the "t:" dictionary.
	    v = find_var_in_ht(&tp->tp_vars->dv_hashtab, 't', varname, FALSE);
	    if (v != NULL)
	    {
		copy_tv(&v->di_tv, rettv);
		done = TRUE;
	    }
	}

	// restore previous notion of curwin
	restore_win(oldcurwin, oldtabpage, TRUE);
    }

    if (!done && argvars[2].v_type != VAR_UNKNOWN)
	copy_tv(&argvars[2], rettv);
}

/*
 * "gettabwinvar()" function
 */
    void
f_gettabwinvar(typval_T *argvars, typval_T *rettv)
{
    getwinvar(argvars, rettv, 1);
}

/*
 * "getwinvar()" function
 */
    void
f_getwinvar(typval_T *argvars, typval_T *rettv)
{
    getwinvar(argvars, rettv, 0);
}

/*
 * "getbufvar()" function
 */
    void
f_getbufvar(typval_T *argvars, typval_T *rettv)
{
    buf_T	*buf;
    char_u	*varname;
    dictitem_T	*v;
    int		done = FALSE;

    varname = tv_get_string_chk(&argvars[1]);
    buf = tv_get_buf_from_arg(&argvars[0]);

    rettv->v_type = VAR_STRING;
    rettv->vval.v_string = NULL;

    if (buf != NULL && varname != NULL)
    {
	if (*varname == '&')
	{
	    buf_T	*save_curbuf = curbuf;

	    // set curbuf to be our buf, temporarily
	    curbuf = buf;

	    if (varname[1] == NUL)
	    {
		// get all buffer-local options in a dict
		dict_T	*opts = get_winbuf_options(TRUE);

		if (opts != NULL)
		{
		    rettv_dict_set(rettv, opts);
		    done = TRUE;
		}
	    }
	    else if (eval_option(&varname, rettv, TRUE) == OK)
		// buffer-local-option
		done = TRUE;

	    // restore previous notion of curbuf
	    curbuf = save_curbuf;
	}
	else
	{
	    // Look up the variable.
	    if (*varname == NUL)
		// Let getbufvar({nr}, "") return the "b:" dictionary.
		v = &buf->b_bufvar;
	    else
		v = find_var_in_ht(&buf->b_vars->dv_hashtab, 'b',
							       varname, FALSE);
	    if (v != NULL)
	    {
		copy_tv(&v->di_tv, rettv);
		done = TRUE;
	    }
	}
    }

    if (!done && argvars[2].v_type != VAR_UNKNOWN)
	// use the default value
	copy_tv(&argvars[2], rettv);
}

/*
 * "settabvar()" function
 */
    void
f_settabvar(typval_T *argvars, typval_T *rettv UNUSED)
{
    tabpage_T	*save_curtab;
    tabpage_T	*tp;
    char_u	*varname, *tabvarname;
    typval_T	*varp;

    if (check_secure())
	return;

    tp = find_tabpage((int)tv_get_number_chk(&argvars[0], NULL));
    varname = tv_get_string_chk(&argvars[1]);
    varp = &argvars[2];

    if (varname != NULL && varp != NULL && tp != NULL)
    {
	save_curtab = curtab;
	goto_tabpage_tp(tp, FALSE, FALSE);

	tabvarname = alloc(STRLEN(varname) + 3);
	if (tabvarname != NULL)
	{
	    STRCPY(tabvarname, "t:");
	    STRCPY(tabvarname + 2, varname);
	    set_var(tabvarname, varp, TRUE);
	    vim_free(tabvarname);
	}

	// Restore current tabpage
	if (valid_tabpage(save_curtab))
	    goto_tabpage_tp(save_curtab, FALSE, FALSE);
    }
}

/*
 * "settabwinvar()" function
 */
    void
f_settabwinvar(typval_T *argvars, typval_T *rettv UNUSED)
{
    setwinvar(argvars, 1);
}

/*
 * "setwinvar()" function
 */
    void
f_setwinvar(typval_T *argvars, typval_T *rettv UNUSED)
{
    setwinvar(argvars, 0);
}

/*
 * "setbufvar()" function
 */
    void
f_setbufvar(typval_T *argvars, typval_T *rettv UNUSED)
{
    buf_T	*buf;
    char_u	*varname, *bufvarname;
    typval_T	*varp;

    if (check_secure())
	return;
    varname = tv_get_string_chk(&argvars[1]);
    buf = tv_get_buf_from_arg(&argvars[0]);
    varp = &argvars[2];

    if (buf != NULL && varname != NULL && varp != NULL)
    {
	if (*varname == '&')
	{
	    aco_save_T	aco;

	    // set curbuf to be our buf, temporarily
	    aucmd_prepbuf(&aco, buf);

	    set_option_from_tv(varname + 1, varp);

	    // reset notion of buffer
	    aucmd_restbuf(&aco);
	}
	else
	{
	    bufvarname = alloc(STRLEN(varname) + 3);
	    if (bufvarname != NULL)
	    {
		buf_T *save_curbuf = curbuf;

		curbuf = buf;
		STRCPY(bufvarname, "b:");
		STRCPY(bufvarname + 2, varname);
		set_var(bufvarname, varp, TRUE);
		vim_free(bufvarname);
		curbuf = save_curbuf;
	    }
	}
    }
}

/*
 * Get a callback from "arg".  It can be a Funcref or a function name.
 * When "arg" is zero return an empty string.
 * "cb_name" is not allocated.
 * "cb_name" is set to NULL for an invalid argument.
 */
    callback_T
get_callback(typval_T *arg)
{
    callback_T  res;
    int		r = OK;

    res.cb_free_name = FALSE;
    if (arg->v_type == VAR_PARTIAL && arg->vval.v_partial != NULL)
    {
	res.cb_partial = arg->vval.v_partial;
	++res.cb_partial->pt_refcount;
	res.cb_name = partial_name(res.cb_partial);
    }
    else
    {
	res.cb_partial = NULL;
	if (arg->v_type == VAR_STRING && arg->vval.v_string != NULL
					       && isdigit(*arg->vval.v_string))
	    r = FAIL;
	else if (arg->v_type == VAR_FUNC || arg->v_type == VAR_STRING)
	{
	    // Note that we don't make a copy of the string.
	    res.cb_name = arg->vval.v_string;
	    func_ref(res.cb_name);
	}
	else if (arg->v_type == VAR_NUMBER && arg->vval.v_number == 0)
	    res.cb_name = (char_u *)"";
	else
	    r = FAIL;

	if (r == FAIL)
	{
	    emsg(_("E921: Invalid callback argument"));
	    res.cb_name = NULL;
	}
    }
    return res;
}

/*
 * Copy a callback into a typval_T.
 */
    void
put_callback(callback_T *cb, typval_T *tv)
{
    if (cb->cb_partial != NULL)
    {
	tv->v_type = VAR_PARTIAL;
	tv->vval.v_partial = cb->cb_partial;
	++tv->vval.v_partial->pt_refcount;
    }
    else
    {
	tv->v_type = VAR_FUNC;
	tv->vval.v_string = vim_strsave(cb->cb_name);
	func_ref(cb->cb_name);
    }
}

/*
 * Make a copy of "src" into "dest", allocating the function name if needed,
 * without incrementing the refcount.
 */
    void
set_callback(callback_T *dest, callback_T *src)
{
    if (src->cb_partial == NULL)
    {
	// just a function name, make a copy
	dest->cb_name = vim_strsave(src->cb_name);
	dest->cb_free_name = TRUE;
    }
    else
    {
	// cb_name is a pointer into cb_partial
	dest->cb_name = src->cb_name;
	dest->cb_free_name = FALSE;
    }
    dest->cb_partial = src->cb_partial;
}

/*
 * Copy callback from "src" to "dest", incrementing the refcounts.
 */
    void
copy_callback(callback_T *dest, callback_T *src)
{
    dest->cb_partial = src->cb_partial;
    if (dest->cb_partial != NULL)
    {
	dest->cb_name = src->cb_name;
	dest->cb_free_name = FALSE;
	++dest->cb_partial->pt_refcount;
    }
    else
    {
	dest->cb_name = vim_strsave(src->cb_name);
	dest->cb_free_name = TRUE;
	func_ref(src->cb_name);
    }
}

/*
 * Unref/free "callback" returned by get_callback() or set_callback().
 */
    void
free_callback(callback_T *callback)
{
    if (callback->cb_partial != NULL)
    {
	partial_unref(callback->cb_partial);
	callback->cb_partial = NULL;
    }
    else if (callback->cb_name != NULL)
	func_unref(callback->cb_name);
    if (callback->cb_free_name)
    {
	vim_free(callback->cb_name);
	callback->cb_free_name = FALSE;
    }
    callback->cb_name = NULL;
}

#endif // FEAT_EVAL