pdmp file _is_ their answer for this day and age! Until version Emacs 26 (which is what Debian oldstable has), they used unexec, the thing that made sense 20 (or 30) years ago, and I think it just would have failed completely in this case because there's nothing to delete. Posted 22:32 UTC (Tue) by geofft (subscriber, #59789)Īpparently the. (Not even on Windows.) But as soon as your use case gets a bit more complicated, you'll need to take this into account.

Now obviously not everyone uses offset/fixed addresses, and if you just want to map an entire file (or at least a region that starts at offset 0), you don't have to care about the page size, and you'll never need to query it. (Or worse, tries to be clever, and uses per-arch/os #ifdefs instead of querying them at runtime.) But I've also stumbled upon a lot of other code on the internet that just hard-codes these values. I've written quite a bit of code that makes use of mmap() (especially for shared memory IPC) and I made sure to always follow the best practices here and dynamically query the OS for the correct alignments when needed. (But don't hard-code those numbers, it's possible to query this at runtime.) > addr must be suitably aligned: for most architectures a multiple of the page size is sufficient however, some architectures may impose additional restrictions.įurthermore, while this isn't relevant to this specific thread, but if you want to write portable code and also support Windows, it uses a page size of 4kiB of x86_64, but requires all virtual memory mappings to be aligned to 64kiB. > offset must be a multiple of the page size as returned by sysconf(_SC_PAGE_SIZE).Īlso, if you use MAP_FIXED (or MAP_FIXED_NOREPLACE), you have Can you give some examples? I've worked some with mmap using applications and I can't think of much where they have dependencies on page size

Emacs mac m1