Are delphi variables initialized with a value by default?

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Yes, this is the documented behaviour:

  • Object fields are always initialized to 0, 0.0, ”, False, nil or whatever applies.

  • Global variables are always initialized to 0 etc as well;

  • Local reference-counted* variables are always initialized to nil or ”;

  • Local non reference-counted* variables are uninitialized so you have to assign a value before you can use them.

I remember that Barry Kelly somewhere wrote a definition for “reference-counted”, but cannot find it any more, so this should do in the meantime:

reference-counted == that are reference-counted themselves, or
directly or indirectly contain fields (for records) or elements (for
arrays) that are reference-counted like: string, variant, interface
or dynamic array or static array containing such types.

Notes:

  • record itself is not enough to become reference-counted
  • I have not tried this with generics yet

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