On 2017-04-15 17:24:54 -0400, Tom Lane wrote: > Andres Freund <and...@anarazel.de> writes: > > On 2017-04-15 17:09:38 -0400, Tom Lane wrote: > >> Why doesn't Windows' ability to map the segment into the new process > >> before it executes take care of that? > > > Because of ASLR of the main executable (i.e. something like PIE). > > Not following. Are you saying that the main executable gets mapped into > the process address space immediately, but shared libraries are not?
Without PIE/ASLR we can somewhat rely on pgwin32_ReserveSharedMemoryRegion to find the space that PGSharedMemoryCreate allocated still unoccupied. If the main binary also uses ASLR, not just libraries/stack/other mappings, that's not guaranteed to be the case. But this probably needs somebody with actual windows expertise commenting. > I wonder whether we could work around that by just destroying the created > process and trying again if we get a collision. It'd be a tad > inefficient, but hopefully collisions wouldn't happen often enough to be a > big problem. That might work, although it's obviously not pretty. We could also just default to some out-of-the-way address for MapViewOfFileEx, that might also work. - Andres -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
