shmget() throws SIGSYS on iOS
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I'm trying to construct a block of shared memory on iOS. It compiles and links, but `shmget()` throws a SIGSYS signal on the most innocent parameters:

    NSString *p = [[NSBundle mainBundle] pathForResource:@"crash" ofType: nil];
    key_t tok = ftok([p UTF8String], 918273);
    int mid = shmget(tok, 4096, IPC_CREAT|S_IRUSR|S_IWUSR);

`tok` is a large positive integer, not -1. Size - tried 1024, same effect.

Is SysV shared memory even supported on iOS? The headers and the libraries are present, or compiler/linker would complain. Same code works on the simulator. What am I doing wrong?