Bug #65987 [Ver->Ana]: memory leak and handle leak in shmop

Edit report at https://bugs.php.net/bug.php?id=65987&edit=1 ID: 65987 Updated by: cmb@php.net Reported by: sakamoto dot ta at saxa dot co dot jp Summary: memory leak and handle leak in shmop -Status: Verified +Status: Analyzed Type: Bug Package: *Extensibility Functions Operating System: Windows PHP Version: Irrelevant Block user comment: N Private report: N New Comment: Well, the actual reason for this behavior is that our Windows implementation of the shm*() functions is rather different from the POSIX semantics, where shared memory is persistent, i.e. it is retained even if all handles have been closed. That is not the case on Windows; if the last handle is closed, the shared memory is freed. So shmop_delete() is actually supposed to be a NOP there. However, shmop_close() does not close all handles to the shared memory on Windows, because re-opening from the same process would no longer be possible. This cannot be changed in a revision release due to BC concerns. It may be reasonable to more closely match POSIX semantics in PHP 8. This would require to create file mappings to actual files on disk, instead of page-file backed memory. As the shared memory would then be persistent, shmop_close() could actually close all handles, and shmop_delete() could be implemented in a way that would delete the backing file on disk after all handles had been closed. Previous Comments: ------------------------------------------------------------------------ [2018-09-18 17:05:52] cmb@php.net I can confirm that shmop_delete() still does not work on Windows with current master. The culprit appears to be the refcount (.shm_nattac) check[1]; it seems to me this can't possibly work, since shmop_open() calls shmat() which increases the refcount, so it is always greater than 1. [1] <https://github.com/php/php-src/blob/php-7.3.0RC1/TSRM/tsrm_win32.c#L757> ------------------------------------------------------------------------ [2018-09-18 17:02:54] cmb@php.net Related To: Bug #75812 ------------------------------------------------------------------------ [2018-09-18 17:01:56] cmb@php.net Related To: Bug #71921 ------------------------------------------------------------------------ [2018-09-18 17:01:08] cmb@php.net Related To: Bug #67524 ------------------------------------------------------------------------ [2013-10-29 00:42:37] sakamoto dot ta at saxa dot co dot jp Description: ------------ OS：Windows 2008 Server R2 PHP:Version 5.3.9 I received an answer and add shmop_delete the case () in Bug # 65949, but it does not improve. Application error occurs when continue to operate the following script. When I call the () shm_close the () shm_open, handle name \BaseNamedObjects\TSRM_SHM_DESCRIPTOR:x and \BaseNamedObjects\TSRM_SHM_SEGMENT:x remains without being released. The amount of memory used will continue to increase. This problem does not occur on Linux. Test script: --------------- <?php $shm_id = 0; $hex_shm_id = 0xff3; $write_d1 = "test #1 of the shmop() extension"; $write_d2 = "test #2 append data to shared memory segment"; for( ; ; ) { echo "shm open for create : "; $shm_id = shmop_open($hex_shm_id, "c", 0644, 1024); if (!$shm_id) { die("failed\n"); } else { echo "ok[".$shm_id."]\n"; } echo "shm size is: " . ($shm_size = shmop_size($shm_id)) . "\n"; echo "shm write test #1: "; $written = shmop_write($shm_id, $write_d1, 0); if ($written != strlen($write_d1)) { echo "failed\n"; } else { echo "ok\n"; } echo "data in memory is: " . shmop_read($shm_id, 0, $written) . "\n"; // Add Next 2 Lines $delete_result = shmop_delete($shm_id); echo "shmop_delete return value [".$delete_result."]\n"; shmop_close($shm_id); $shm_id = 0; sleep(1); } ?> Expected result: ---------------- Memory leak and handle leak does not occur. ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=65987&edit=1