4 ms·

Global state is a feature, not a bug. It's absolutely necessary for a number of application domains and disallowing it by design makes the V language totally un

Global state is a feature, not a bug. It's absolutely necessary for a number of application domains and disallowing it by design makes the V language totally unsuited for them

ithkuil 7y ago
I'm curious, can you make an example?
- holy_city 7y ago
  POSIX signal handlers don't take an argument other than the signal code, so if you want to handle them gracefully in a stateful app you need a global to communicate the trapped signal to your main loop.
  - ithkuil 7y ago
    Closures could be used to implement this use case, provided that they can be exported/represented as native C function pointets, e.g. via a trampoline that captures the necessary captured context)
    - holy_city 7y ago
      How would you implement the trampoline without a global? And would the captured context not count as a global? In C the only memory available to a function is its arguments and data with static duration. That static storage is synonymous with global state, if it isn't known at compile time.
      - ithkuil 7y ago
        We have to distinguish what the given language exposes to its users and how the code such language generated works on the underlying hardware (along with constraints due to compatibility with other languages, most importantly C which is the de-facto system interface nowadays). A C-compatible closure basically requires an executable chunk of memory that captures the state along with the istructions to push it to the parameters area (based on the architecture's calling convention) and then jumping to the actual function. This is not global just because it's scoping the state with the function. On the other hand it becomes global the moment it gets installed to a global handler table (because there can only be one such handler). However a language that limits globals (and forces people through this kind of hoops in order to deal with cases where singletons are really needed) encourages a coding style that makes it easier to test your code in isolation.
pier25 7y ago
I'm guessing you still are able to use a singleton, no?
- holy_city 7y ago
  Singletons still require globals. I haven't really dug into V that much, is there a mechanism to make a singleton? If so, how can they claim "no global variables?"
sagichmal 7y ago
There is not a single situation where global variables are necessary.
- crankylinuxuser 7y ago
  I take it you've never programmed embedded? Yeah, state sucks. But sometimes, you need a starting point, and diff from that. And, that's state. One of the safe ways of handling global vars, is by having only a single non-interruptible function that can mutate global. And you have best make sure your global-mutating function is fast. You don't want to miss IRQs that might fire off but are blocked.
  - sagichmal 7y ago
    Yes, embedded is enough of a special case that I don’t consider it as part of a general purpose discussion on programming languages.
    - mises 7y ago
      Ericsson predicts 18 billion IoT devices by 2022. Those all need code written for them. Do you still consider embedded programming a "niche"? Maybe it's one specific case, but it's relevant and ought to be "part of the discussion". https://www.ericsson.com/en/mobility-report/internet-of-things-forecast https://www.ericsson.com/en/mobility-report/internet-of-thin...
- holy_city 7y ago
  Global logging in libraries is not uncommon, especially if you need to trap signals (which can only interact with global state). COM APIs expose a global class factory as the main interface to a shared libraries. Embedded systems and drivers require globals in one form or another. "Globals are evil" comes from the fact that globals have side effects, and side effects make things hard, especially in modern software that utilizes asynchronous/concurrent logic. That just makes them unwieldy, not unnecessary. Especially when interacting with legacy systems that require globals.
crankylinuxuser 7y ago
Eh, not a big deal. Just move "global" (aka: main() ) up 1 function. And then, run everything in that function. Hell, it could be a try-catch loop equivalent.
- holy_city 7y ago
  That kind of assumes you have a main() function.

Global state is a feature, not a bug. It's absolutely necessary for a number of application domains and disallowing it by design makes the V language totally unsuited for them

ithkuil 7y ago

I'm curious, can you make an example?

holy_city 7y ago
POSIX signal handlers don't take an argument other than the signal code, so if you want to handle them gracefully in a stateful app you need a global to communicate the trapped signal to your main loop.
- ithkuil 7y ago
  Closures could be used to implement this use case, provided that they can be exported/represented as native C function pointets, e.g. via a trampoline that captures the necessary captured context)
  - holy_city 7y ago
    How would you implement the trampoline without a global? And would the captured context not count as a global? In C the only memory available to a function is its arguments and data with static duration. That static storage is synonymous with global state, if it isn't known at compile time.
    - ithkuil 7y ago
      We have to distinguish what the given language exposes to its users and how the code such language generated works on the underlying hardware (along with constraints due to compatibility with other languages, most importantly C which is the de-facto system interface nowadays). A C-compatible closure basically requires an executable chunk of memory that captures the state along with the istructions to push it to the parameters area (based on the architecture's calling convention) and then jumping to the actual function. This is not global just because it's scoping the state with the function. On the other hand it becomes global the moment it gets installed to a global handler table (because there can only be one such handler). However a language that limits globals (and forces people through this kind of hoops in order to deal with cases where singletons are really needed) encourages a coding style that makes it easier to test your code in isolation.

pier25 7y ago

I'm guessing you still are able to use a singleton, no?

holy_city 7y ago
Singletons still require globals. I haven't really dug into V that much, is there a mechanism to make a singleton? If so, how can they claim "no global variables?"

sagichmal 7y ago

There is not a single situation where global variables are necessary.

crankylinuxuser 7y ago
I take it you've never programmed embedded? Yeah, state sucks. But sometimes, you need a starting point, and diff from that. And, that's state. One of the safe ways of handling global vars, is by having only a single non-interruptible function that can mutate global. And you have best make sure your global-mutating function is fast. You don't want to miss IRQs that might fire off but are blocked.
- sagichmal 7y ago
  Yes, embedded is enough of a special case that I don’t consider it as part of a general purpose discussion on programming languages.
  - mises 7y ago
    Ericsson predicts 18 billion IoT devices by 2022. Those all need code written for them. Do you still consider embedded programming a "niche"? Maybe it's one specific case, but it's relevant and ought to be "part of the discussion". https://www.ericsson.com/en/mobility-report/internet-of-things-forecast https://www.ericsson.com/en/mobility-report/internet-of-thin...
holy_city 7y ago
Global logging in libraries is not uncommon, especially if you need to trap signals (which can only interact with global state). COM APIs expose a global class factory as the main interface to a shared libraries. Embedded systems and drivers require globals in one form or another. "Globals are evil" comes from the fact that globals have side effects, and side effects make things hard, especially in modern software that utilizes asynchronous/concurrent logic. That just makes them unwieldy, not unnecessary. Especially when interacting with legacy systems that require globals.

crankylinuxuser 7y ago

Eh, not a big deal. Just move "global" (aka: main() ) up 1 function. And then, run everything in that function. Hell, it could be a try-catch loop equivalent.

holy_city 7y ago
That kind of assumes you have a main() function.