Disturbing: const QString &

[magland]

I recently found a bug in one of my programs... and it's disturbing to me, so I'd like some comments.

Suppose I have a function which takes QString as an argument, and I don't change the value of the argument in the function, so I set it as const (is that what const means by the way?... that the function is not allowed to change the value of it?).

But the function happened to be recursive, and it called itself with another value of the parameter. This caused UNEXPECTED BEHAVIOR! I can't describe exactly what happens, but the values changed right in the middle of the function!

void myfunction(const QString &val) {
  ...
  QString val2=...;
  ...
  myfunction(val2);
  [Here's where val changed!]
  ...
}

void myfunction(const QString &val) {
  ...
  QString val2=...;
  ...
  myfunction(val2);
  [Here's where val changed!]
  ...
}

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Am I misunderstanding something?