Mirror of forum.nim-lang.org

820 :: Global variables

• immortal (orginal) [2015-02-02T02:23:33+01:00] view original

  What is the correct way to declare a global variable so that I can access it within two or more procs and modify it's value. I read about global variables in the docs but I can't figure out how to actually use them.

---

• fadg44a3w4fe (orginal) [2015-02-02T02:38:06+01:00] view original

  var i = 0 proc p1() = i += 1 proc p2() = i += 2

  Run

---

• immortal (orginal) [2015-02-02T02:55:17+01:00] view original

  Would this allow me to access the global variable from within a proc spawned by a thread?

  
  
  import threadpool
  
  var test = "hi"
  proc p1(variable) =
    test = "bye"
  var variable = "test"
  spawn(p1(variable))
  
  Ends up with:
  t.nim(7, 8) Error: 'spawn' takes a GC safe call expression
  Run

---

• fadg44a3w4fe (orginal) [2015-02-02T03:04:54+01:00] view original

  No, because the GC uses thread-local heaps and would therefore have no idea when to free the variable contents. You could try using http://nim-lang.org/channels.html though. It's also possible to access it if you use http://nim-lang.org/system.html#allocShared0,int and manually free your memory.

---

• immortal (orginal) [2015-02-02T03:16:56+01:00] view original

  Using the {.threadvar.} pragma solved my issue of global variables accessed within threads. Thanks!

---