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8962 :: cstring has different behavior in different MM mode

• haoliang (orginal) [2022-02-27T19:34:11+01:00] view original

  as we know, string in nim is value type, but i do not know the type of cstring. so i wrote a snippet:

  var y = "abc"
  let z = cstring(y)
  y.add("d")
  
  # when mm:arc
  # assert y == "abcd"
  # assert z == cstring"abc"
  
  # when mm:refc
  assert y == "abcd"
  assert z == cstring"abcd"
  Run

  when mm == refc, it's like a ref or ptr; but when mm == arc, it's like a value type; i was so confused. thanks for help!

  ps: this question was originated from this pr that says there is a memory leak with cstring.

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• xigoi (orginal) [2022-02-27T20:03:57+01:00] view original

  Maybe there should be a collection of “gotchas” like this?

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• Araq (orginal) [2022-02-28T07:34:54+01:00] view original

  The code is invalid regardless of the used mm scheme. It never was correct and cstring is always a pointer and string always a value type.

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