[php-src] Issue #9944: Windows C shmget(IPC_PRIVATE, ...) returns IPC_PRIVATE(0) instead of distinct id for new section

Issue: https://github.com/php/php-src/issues/9944 Author: TysonAndre ### Description The following code: https://github.com/php/php-src/blob/php-8.2.0RC6/TSRM/tsrm_win32.c#L613-L683 ```c size_t size = 8192; key_t key = IPC_PRIVATE; /* shm key */ oflag = IPC_CREAT | SHM_R | SHM_A; if ((shmid = shmget(key, size, oflag)) < 0) { zend_error_noreturn(E_CORE_ERROR, "shmget failed"); } fprintf(stderr, "shmid %d\n", shmid); ``` Resulted in this output because nothing sets key for IPC_PRIVATE: ``` shmid 0 ``` But I expected this output instead: ``` shmid $distinct_nonzero_integer ``` If code calls shmget(IPC_PRIVATE) multiple times on Windows and gets IPC_PRIVATE as a result, applications would need distinct ids to distinguish them in operations managing the shared memory segments - A symptom can be seen is that shmctl would fail to be set on the right shared memory segment because there are distinct segments with the same id of 0 https://github.com/php/php-src/blob/php-8.2.0RC6/TSRM/tsrm_win32.c#L722 - On linux with the real shmget() i'd get identifiers such as 3964933, 3964935 and pointers such as 0x7ff0dbe1f000, 0x7ff0eca55000 for multiple calls to fetch IPC_PRIVATE Related to https://github.com/php/php-src/issues/9829 - I believe TSRM/tsrm_win32.c for windows didn't attempt to support IPC_PRIVATE in PHP versions prior to that Noticed while investigating https://github.com/krakjoe/apcu/issues/445 when using more than one shared segment ``` if (flags & IPC_CREAT) { shm_handle = CreateFileMapping(INVALID_HANDLE_VALUE, NULL, PAGE_READWRITE, high, low, key == IPC_PRIVATE ? NULL : shm_segment); ``` It seems like it should immediately choose a distinct id if key == IPC_PRIVATE - it'd be clobbering the existing entry with the key 0, which would prevent detaching segments other than the most recent one created with IPC_PRIVATE https://github.com/php/php-src/blob/php-8.2.0RC6/TSRM/tsrm_win32.c#L652-L657 ----- https://man7.org/linux/man-pages/man2/shmget.2.html ``` RETURN VALUE [top](https://man7.org/linux/man-pages/man2/shmget.2.html#top_of_page) On success, a valid shared memory identifier is returned. On error, -1 is returned, and [errno](https://man7.org/linux/man-pages/man3/errno.3.html) is set to indicate the error. DESCRIPTION shmget() returns the identifier of the System V shared memory segment associated with the value of the argument key. It may be used either to obtain the identifier of a previously created shared memory segment (when shmflg is zero and key does not have the value IPC_PRIVATE), or to create a new set. A new shared memory segment, with size equal to the value of size rounded up to a multiple of PAGE_SIZE, is created if key has the value IPC_PRIVATE or key isn't IPC_PRIVATE, no shared memory segment corresponding to key exists, and IPC_CREAT is specified in shmflg. ``` ### PHP Version 8.2 ### Operating System Windows