Re: Let's drop support for named POSIX semaphores

Greg Burd <greg(at)burd(dot)me> writes:
> Peter, as to your concern that this adds another hard SysV dependency
> and so cuts against the work to let PostgreSQL run without SysV IPC (for
> macOS sandboxing): I don't think removing *named* POSIX semaphores costs
> that effort anything, because named POSIX semaphores are not the thing
> that effort would reach for.

> The non-SysV semaphore path we'd actually want is the *unnamed* kind
> (sem_init), which posix_sema.c already prefers and which backs the sem_t
> structs out of shared memory.

... and which macOS still doesn't support :-(. But moving from SysV
to named POSIX semaphores isn't realistic performance-wise, so we need
some other path altogether if we hope to address the sandboxing
problem.

> (+1 as well to Shihao's two nits, the now-unused IPCProtection macro
> and the stale runtime.sgml line about which platforms use which.)

Yeah, I noticed a few comments that need updates as well.

regards, tom lane