nimforum mirror - Is it possible to detect context in relation to a threadvar?

JohnAD (orginal) [2019-09-04T21:12:46+02:00] view original

I'm developing a library that maintains a global pool of resources that can be seen in both thread and non-threaded contexts. Rather than jump into great detail, let show this with a silly example:

import strutils
import jester

var someGlobal: string = "value at the moment"

var someThread {.threadvar.}: string

proc getSomeMain(): string =
  result = "copy of $1".format(someGlobal)

proc getSomeFromThread(): string {.gcsafe.} =
  someThread = "copy of $1".format(someGlobal)
  return someThread

someGlobal = "another change"

var x = getSomeMain()
echo x

routes:
  get "/":
    var y = getSomeFromThread()
    resp y

Everything works great.

But, I ask, would it be possible to write a generic equivalent of "getSome". Something like:

proc getSome(): string =
  if MAGIC_DETECT_METHOD:
    return "copy of $1".format(someGlobal)
  else:
    someThread = "copy of $1".format(someGlobal)
    return someThread

Or, if not at runtime, some kind of compile-time thing that detects whether "getSome" is being called from a thread, such as a Macro or Template.

I apologize if the answer to this is well documented somewhere. I've not been able to find an answer yet.

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5169 :: Is it possible to detect context in relation to a threadvar?