Avoid modifying the return value of readline_completion_function()

[cmb69]

The internal function _readline_command_generator() modifies the
internal array pointer of readline_completion_function()'s return
value. We therefore separate the array, what also avoids failing
assertions regarding the array refcount.

[nikic]

Can we switch it to use ZEND_HASH_FOREACH instead?

[cmb69]

The array pointer is advanced only one element for every executed callback:

php-src/ext/readline/readline.c

Lines 512 to 531 in d1b1c04

	static char *_readline_command_generator(const char *text, int state)
	{
	HashTable *myht = Z_ARRVAL(_readline_array);
	zval *entry;
	if (!state) {
	zend_hash_internal_pointer_reset(myht);
	}
	while ((entry = zend_hash_get_current_data(myht)) != NULL) {
	zend_hash_move_forward(myht);
	convert_to_string_ex(entry);
	if (strncmp (Z_STRVAL_P(entry), text, strlen(text)) == 0) {
	return (strdup(Z_STRVAL_P(entry)));
	}
	}
	return NULL;
	}

We could store an external HashPosition, and use that API, but I'm not sure whether that would be a real improvement.

[nikic]

Right, that makes sense.

It's also not just the array pointer, we also convert elements to string.