[fpc-devel] Wrong docs: not initialized global variables

[Maciej Izak]

2018-03-24 20:49 GMT+01:00 Ondrej Pokorny <lazarus at kluug.net>:

> Does it mean I can assume a local string variable is always (=whenever the
> routine is called) initialized to ''? I.e. that TestB always returns 'a'?
>
> function TestB: string;
> var B: string;
> begin
>   B := B + 'a';
>   Result := B;
> end;
>
> Until now I though that the above code is unsafe and I always initialized
> all local variables (also managed) before use. I assumed the initialization
> to empty string does not need to happen at every routine call.
>

Please note that string/dynamic array as Result is exception (it works like
*var* parameter). IMO this is the ugliest Pascal behavior ever:

=== example begin ===
function test1: string;
begin
  Result := Result + 'a';
end;

function test2: TArray<byte>;
begin
  SetLength(Result, Length(Result) + 1);
end;

begin
  writeln(test1); // print a
  writeln(test1); // print aa
  writeln(test1); // print aaa
  writeln(test1); // print aaaa
  writeln(Length(test2)); // print 1
  writeln(Length(test2)); // print 2
  writeln(Length(test2)); // print 3
  writeln(Length(test2)); // print 4
end.
=== example end ===

-- 
Best regards,
Maciej Izak
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