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RichFelker's profile
Rich Felker
Rich Felker
Rich Felker
@RichFelker

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Rich Felker

@RichFelker

Yeah, I do @musllibc, FOSS & infosec stuff. But now is not the time for a mostly-/only-tech Twitter feed.

musl-libc.org
Joined March 2014

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    1. John Regehr‏ @johnregehr Jul 16
      Replying to @RichFelker @jfbastien @incomputable

      peek and poke (I'm serious, but not about the function names)

      4 replies 0 retweets 3 likes
    2. Rich Felker‏ @RichFelker Jul 16
      Replying to @johnregehr @jfbastien @incomputable

      But you can't implement peek and poke without asm then. The great advancement of mmio was that you *can* write code driving memory-mapped devices purely in C (or C++) without needing hideous inb/outb/inw/outw/etc. asm.

      2 replies 0 retweets 1 like
    3. John Regehr‏ @johnregehr Jul 16
      Replying to @RichFelker @jfbastien @incomputable

      peek and poke are library functions or just use asm. I've written a ton of microcontroller code and there is zero sense in pretending that code accessing memory-mapping i/o is portable

      1 reply 0 retweets 4 likes
    4. Rich Felker‏ @RichFelker Jul 16
      Replying to @johnregehr @jfbastien @incomputable

      Except all the modern mmio drivers in Linux *just work* on all archs, even ones they were never designed for. Essentially, they *are* portable. This was not the case with old io-insn stuff.

      2 replies 0 retweets 1 like
    5. Rich Felker‏ @RichFelker Jul 16
      Replying to @RichFelker @johnregehr and

      Yes you could achieve the same with peek and poke functions for each bus access size, but unless they were part of the stdlib you'd have all sorts of gratuitous portability problems from ppl implementing their own just for arm and x86.

      1 reply 0 retweets 0 likes
    6. John Regehr‏ @johnregehr Jul 16
      Replying to @RichFelker @jfbastien @incomputable

      maybe we should quibble about a specific piece of code-- do you have one in mind? my guess is that the implementation style is already pretty close to what I want. all I'm really talking about is replacing x = 1 where x is volatile with poke(x, 1).

      3 replies 0 retweets 2 likes
    7. Rich Felker‏ @RichFelker Jul 16
      Replying to @johnregehr @jfbastien @incomputable

      If we were designing the language from scratch today, no objection at all. OTOH if the request is "remove volatile [and force everyone to replace it with non-portable hacks]" I have a big problem with that.

      1 reply 0 retweets 0 likes
    8. John Regehr‏ @johnregehr Jul 16
      Replying to @RichFelker @jfbastien @incomputable

      yes to eventually forcing everyone to move away from volatile, but that would be a long time from now. no to non-portable hacks -- the volatile replacement would be precisely as portable as the current code, just with explicit loads/stores instead of implicit ones.

      2 replies 0 retweets 1 like
    9. Francisco Lopes‏ @pepper_chico Jul 16
      Replying to @johnregehr @RichFelker and

      As formerly pointed, today peek and poke can be implemented in C due to volatile, and final user can have their peek and poke API. Removing volatile equates to obligatory peek and poke APIs + no C implementation.

      1 reply 0 retweets 1 like
    10. John Regehr‏ @johnregehr Jul 16
      Replying to @pepper_chico @RichFelker and

      exactly

      1 reply 0 retweets 0 likes
      Rich Felker‏ @RichFelker Jul 16
      Replying to @johnregehr @pepper_chico and

      The whole model of MMIO makes no sense without volatile types. Hypothetical peek/poke functions would have no reason to take pointer arguments you couldn't validly dereference anyway. They would take some sort of integer address arguments...

      3:55 PM - 16 Jul 2018
      1 reply 0 retweets 0 likes
        1. New conversation
        2. Rich Felker‏ @RichFelker Jul 16
          Replying to @RichFelker @johnregehr and

          And then they don't even look memory-mapped anymore.

          1 reply 0 retweets 0 likes
        3. Francisco Lopes‏ @pepper_chico Jul 16
          Replying to @RichFelker @johnregehr and

          Indeed. Personally, obligating asm implementation by removing a feature of a language whose main purpose was to replace asm is not right for me.

          0 replies 0 retweets 1 like
        4. End of conversation

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