opcache: Disallow changing opcache.memory_consumption when SHM is set up

Normally changing the INI value is not possible after SHM is set up, since it
is `PHP_INI_SYSTEM`. FPM is a notable exception: SHM is set up in the master
process, but when spawning the individual pools, the `php_admin_value` config
option can be used to change `PHP_INI_SYSTEM` INIs on a per-pool basis. This
does not work for this option, since it will only be read on early start,
leading to misleading PHPInfo output, since the INI value appears to be
successfully set and since some of the calculated values are derived from the
INI value rather than the actual value.

Author: TimWolla

NEWS

@@ -2,6 +2,10 @@ PHP                                                                        NEWS
 |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 ?? ??? ????, PHP 8.5.0alpha3
 
+- OPcache:
+  . Disallow changing opcache.memory_consumption when SHM is already set up.
+    (timwolla)
+
 - Sockets:
   . socket_set_option for multicast context throws a ValueError
     when the socket family is not of AF_INET/AF_INET6 family. (David Carlier)

UPGRADING

@@ -571,6 +571,9 @@ PHP 8.5 UPGRADE NOTES
   . The default value of opcache.jit_hot_loop is now 61 (a prime) to prevent it
     from being a multiple of loop iteration counts.
     It is recommended that this parameter is set to a prime number.
+  . Changing opcache.memory_consumption when OPcache SHM is already set up
+    will now correctly report a failure instead of silently doing nothing and
+    showing misleading values in PHPInfo.
 
 - OpenSSL:
   Added openssl.libctx to select the OpenSSL library context type. Either

ext/opcache/zend_accelerator_module.c

@@ -76,6 +76,15 @@ static int validate_api_restriction(void)
 
 static ZEND_INI_MH(OnUpdateMemoryConsumption)
 {
+	if (accel_startup_ok) {
+		if (strcmp(sapi_module.name, "fpm-fcgi") == 0) {
+			zend_accel_error(ACCEL_LOG_WARNING, "opcache.memory_consumption cannot be changed when OPcache is already set up. Are you using php_admin_value[opcache.memory_consumption] in an individual pool's configuration?\n");
+		} else {
+			zend_accel_error(ACCEL_LOG_WARNING, "opcache.memory_consumption cannot be changed when OPcache is already set up.\n");
+		}
+		return FAILURE;
+	}
+
 	zend_long *p = (zend_long *) ZEND_INI_GET_ADDR();
 	zend_long memsize = atoi(ZSTR_VAL(new_value));
 	/* sanity check we must use at least 8 MB */