Description:
------------
disable_functions ini directive can be set before the php engine is initialized here https://github.com/php/php-src/blob/PHP-7.4.6/main/main.c#L2345

but for some reasons, setting/clearing disable_functions ini directive causes currently memory corruptions / php crash.

In the example below I post complete source code of the module where the problem is isolated and it can be produced repeatably by these steps:
1. compile the module
2.a run "php -v" with the module loaded
2.b run https://pastebin.com/NxHCBGmJ with the module loaded and notice "B" is not printed. This issue is presented if at least 195 functions are defined and ini_set() is called. If defined functions count is reduced or ini_set() is not called, full "AB" is printed, otherwise only "A" is printed.

Can you reproduce the issue and is the usage of "zend_alter_ini_entry_chars" function correct? Is there currently a workaround to clear the disable_functions ini from module init?

Test script:
---------------
problematic line:

zend_alter_ini_entry_chars(ini_name_zend, "", strlen(""), PHP_INI_SYSTEM, PHP_INI_STAGE_ACTIVATE);

complete mmm.c / module source:

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "php.h"

PHP_MINIT_FUNCTION(mmm) {
    zend_string *ini_name_zend = zend_string_init("disable_functions", strlen("disable_functions"), 0);
    zend_alter_ini_entry_chars(ini_name_zend, "", strlen(""), PHP_INI_SYSTEM, PHP_INI_STAGE_ACTIVATE);
    zend_string_release_ex(ini_name_zend, 0);

    return SUCCESS;
}

zend_module_entry mmm_module_entry = {
    STANDARD_MODULE_HEADER,
    "mmm",
    NULL,
    PHP_MINIT(mmm),
    NULL,
    NULL,
    NULL,
    NULL,
    "1.0.0",
    STANDARD_MODULE_PROPERTIES
};

ZEND_GET_MODULE(mmm)


Expected result:
----------------
PHP 7.4.5 (cli) (built: Apr 14 2020 16:17:19) ( NTS Visual C++ 2017 x64 )
Copyright (c) The PHP Group
Zend Engine v3.4.0, Copyright (c) Zend Technologies
    with Zend OPcache v7.4.5, Copyright (c), by Zend Technologies


Actual result:
--------------
PHP 7.4.5 (cli) (built: Apr 14 2020 16:17:19) ( NTS Visual C++ 2017 x64 )
Copyright (c) The PHP Group
Zend Engine v3.4.0, Copyright (c) Zend Technologies
    with Zend OPcache v7.4.5, Copyright (c), by Zend Technologies
zend_mm_heap corrupted