hush: make var nesting code independent of "local" support
Also, add code to abort at ~65000 function recursion depth.
SEGVing is not as nice as exiting with a message (and restoring termios!):
$ f() { echo -n .; f; }; f
....<many dots later>....hush: fatal recursion (depth 65281)
function old new delta
run_pipe 1826 1890 +64
pseudo_exec_argv 544 554 +10
parse_and_run_file 71 80 +9
i_getch 104 107 +3
done_command 99 102 +3
set_local_var 508 510 +2
helper_export_local 214 215 +1
builtin_local 49 46 -3
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 7/1 up/down: 92/-3) Total: 89 bytes
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko
parent
61407807ab
commit
332e4115c9
103
shell/hush.c
103
shell/hush.c
@ -730,10 +730,8 @@ struct parse_context {
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struct variable {
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struct variable *next;
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char *varstr; /* points to "name=" portion */
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#if ENABLE_HUSH_LOCAL
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unsigned func_nest_level;
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#endif
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int max_len; /* if > 0, name is part of initial env; else name is malloced */
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uint16_t var_nest_level;
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smallint flg_export; /* putenv should be done on this var */
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smallint flg_read_only;
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};
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@ -922,12 +920,13 @@ struct globals {
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const char *cwd;
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struct variable *top_var;
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char **expanded_assignments;
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#if ENABLE_HUSH_FUNCTIONS
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struct function *top_func;
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# if ENABLE_HUSH_LOCAL
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struct variable **shadowed_vars_pp;
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unsigned func_nest_level;
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unsigned var_nest_level;
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#if ENABLE_HUSH_FUNCTIONS
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# if ENABLE_HUSH_LOCAL
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unsigned func_nest_level; /* solely to prevent "local v" in non-functions */
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# endif
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struct function *top_func;
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#endif
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/* Signal and trap handling */
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#if ENABLE_HUSH_FAST
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@ -2131,7 +2130,7 @@ static const char* FAST_FUNC get_local_var_value(const char *name)
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#define SETFLAG_EXPORT (1 << 0)
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#define SETFLAG_UNEXPORT (1 << 1)
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#define SETFLAG_MAKE_RO (1 << 2)
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#define SETFLAG_LOCAL_SHIFT 3
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#define SETFLAG_VARLVL_SHIFT 3
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static int set_local_var(char *str, unsigned flags)
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{
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struct variable **cur_pp;
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@ -2139,7 +2138,7 @@ static int set_local_var(char *str, unsigned flags)
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char *free_me = NULL;
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char *eq_sign;
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int name_len;
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IF_HUSH_LOCAL(unsigned local_lvl = (flags >> SETFLAG_LOCAL_SHIFT);)
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unsigned local_lvl = (flags >> SETFLAG_VARLVL_SHIFT);
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eq_sign = strchr(str, '=');
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if (!eq_sign) { /* not expected to ever happen? */
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@ -2176,8 +2175,7 @@ static int set_local_var(char *str, unsigned flags)
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unsetenv(str);
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*eq_sign = '=';
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}
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#if ENABLE_HUSH_LOCAL
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if (cur->func_nest_level < local_lvl) {
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if (cur->var_nest_level < local_lvl) {
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/* New variable is declared as local,
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* and existing one is global, or local
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* from enclosing function.
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@ -2197,7 +2195,7 @@ static int set_local_var(char *str, unsigned flags)
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flags |= SETFLAG_EXPORT;
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break;
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}
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#endif
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if (strcmp(cur->varstr + name_len, eq_sign + 1) == 0) {
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free_and_exp:
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free(str);
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@ -2225,7 +2223,7 @@ static int set_local_var(char *str, unsigned flags)
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/* Not found - create new variable struct */
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cur = xzalloc(sizeof(*cur));
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IF_HUSH_LOCAL(cur->func_nest_level = local_lvl;)
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cur->var_nest_level = local_lvl;
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cur->next = *cur_pp;
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*cur_pp = cur;
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@ -5509,7 +5507,7 @@ static struct pipe *parse_stream(char **pstring,
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goto parse_error2;
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default:
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if (HUSH_DEBUG)
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bb_error_msg_and_die("BUG: unexpected %c\n", ch);
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bb_error_msg_and_die("BUG: unexpected %c", ch);
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}
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} /* while (1) */
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@ -7362,8 +7360,9 @@ static void exec_function(char ***to_free,
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// for "more correctness" we might want to close those extra fds here:
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//? close_saved_fds_and_FILE_fds();
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/* "we are in function, ok to use return" */
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/* "we are in a function, ok to use return" */
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G_flag_return_in_progress = -1;
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G.var_nest_level++;
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IF_HUSH_LOCAL(G.func_nest_level++;)
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/* On MMU, funcp->body is always non-NULL */
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@ -7383,6 +7382,47 @@ static void exec_function(char ***to_free,
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# endif
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}
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static void enter_var_nest_level(void)
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{
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G.var_nest_level++;
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/* Try: f() { echo -n .; f; }; f
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* struct variable::var_nest_level is uint16_t,
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* thus limiting recursion to < 2^16.
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* In any case, with 8 Mbyte stack SEGV happens
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* not too long after 2^16 recursions anyway.
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*/
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if (G.var_nest_level > 0xff00)
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bb_error_msg_and_die("fatal recursion (depth %u)", G.var_nest_level);
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}
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static void leave_var_nest_level(void)
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{
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struct variable *cur;
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struct variable **cur_pp;
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cur_pp = &G.top_var;
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while ((cur = *cur_pp) != NULL) {
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if (cur->var_nest_level < G.var_nest_level) {
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cur_pp = &cur->next;
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continue;
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}
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/* Unexport */
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if (cur->flg_export)
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bb_unsetenv(cur->varstr);
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/* Remove from global list */
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*cur_pp = cur->next;
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/* Free */
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if (!cur->max_len)
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free(cur->varstr);
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free(cur);
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}
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G.var_nest_level--;
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if (HUSH_DEBUG && (int)G.var_nest_level < 0)
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bb_error_msg_and_die("BUG: nesting underflow");
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}
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static int run_function(const struct function *funcp, char **argv)
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{
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int rc;
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@ -7394,6 +7434,8 @@ static int run_function(const struct function *funcp, char **argv)
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/* "we are in function, ok to use return" */
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sv_flg = G_flag_return_in_progress;
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G_flag_return_in_progress = -1;
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enter_var_nest_level();
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IF_HUSH_LOCAL(G.func_nest_level++;)
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/* On MMU, funcp->body is always non-NULL */
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@ -7408,30 +7450,9 @@ static int run_function(const struct function *funcp, char **argv)
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rc = run_list(funcp->body);
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}
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# if ENABLE_HUSH_LOCAL
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{
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struct variable *var;
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struct variable **var_pp;
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IF_HUSH_LOCAL(G.func_nest_level--;)
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leave_var_nest_level();
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var_pp = &G.top_var;
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while ((var = *var_pp) != NULL) {
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if (var->func_nest_level < G.func_nest_level) {
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var_pp = &var->next;
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continue;
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}
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/* Unexport */
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if (var->flg_export)
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bb_unsetenv(var->varstr);
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/* Remove from global list */
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*var_pp = var->next;
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/* Free */
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if (!var->max_len)
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free(var->varstr);
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free(var);
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}
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G.func_nest_level--;
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}
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# endif
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G_flag_return_in_progress = sv_flg;
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restore_G_args(&sv, argv);
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@ -9959,8 +9980,8 @@ static int helper_export_local(char **argv, unsigned flags)
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# if ENABLE_HUSH_LOCAL
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/* Is this "local" bltin? */
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if (!(flags & (SETFLAG_EXPORT|SETFLAG_UNEXPORT|SETFLAG_MAKE_RO))) {
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unsigned lvl = flags >> SETFLAG_LOCAL_SHIFT;
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if (var && var->func_nest_level == lvl) {
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unsigned lvl = flags >> SETFLAG_VARLVL_SHIFT;
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if (var && var->var_nest_level == lvl) {
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/* "local x=abc; ...; local x" - ignore second local decl */
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continue;
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}
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@ -10045,7 +10066,7 @@ static int FAST_FUNC builtin_local(char **argv)
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return EXIT_FAILURE; /* bash compat */
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}
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argv++;
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return helper_export_local(argv, G.func_nest_level << SETFLAG_LOCAL_SHIFT);
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return helper_export_local(argv, G.var_nest_level << SETFLAG_VARLVL_SHIFT);
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}
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#endif
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