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

Ondrej Pokorny lazarus at kluug.net
Thu Apr 5 09:12:41 CEST 2018

On 05.04.2018 8:35, Michael Van Canneyt wrote:
>>> Now, it is also correct that the compiler developers are aware that 
>>> many people rely on this implementation detail.
>> Since when is documented behavior considered as "implementation 
>> detail"? This is not an implementation detail. It is in official 
>> documentation.
> You and I know very well that this is an implementation detail, needed
> for internal bookkeeping of the compiler. That the delphi manual states
> otherwise, I have always considered a grave error on their part:
> It contradicts one of the core tenets of pascal - see below.

Huh, no, I don't know this is an implementation detail. For me the 
initialization rules always were:

1.) Global variables are initialized. (Why is simple global variables 
initialization needed for internal bookkeeping of the compiler?)
2.) Class fields are initialized. (Why is simple class fields 
initialization needed for internal bookkeeping of the compiler?)
3.) Everything else is not initialized.

Yes, I have always relied on both 1.+2. For me both points 1.+2. are 
well documented and wanted behavior. Isn't it so?

About point 3: your very own docs state otherwise for managed types (see 
my initial email in this thread) and I was surprised to read it. I am 
not aware the Delphi manual states anything about initializing managed 
types. AFAIK Delphi manual states that the compiler itself cares about 
memory management automatically but it doesn't state anything about when 
initialization or finalization must happen. It doesn't state local 
managed variables are initialized to empty string/nil in particular.

Until now I have never relied on implicitely initialized local 
variables. Your very own docs document the guaranteed local managed 
variable initialization, not Delphi's. If you say it is an 
implementation detail, you must delete it from the docs. For me the 
"grave error" is on FPC's side and not Delphi's.


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