[fpc-devel] Comparison FPC 2.6.2 - Delphi 7

[Michael Schnell]

On 03/06/2013 01:43 PM, Sven Barth wrote:
>
>> And how does one the "current" TThread?
> Since a few weeks: TThread.CurrentThread ;)
>

This does in fact use a threadvar:

threadvar
   { the instance of the current thread; in case of an external thread 
this is
     Nil until TThread.GetCurrentThread was called once (the RTLs need 
to ensure
     that threadvars are initialized with 0!) }
   CurrentThreadVar: TThread;


and (unless the compiler optimizes this out) even accesses it twice:


   if not Assigned(CurrentThreadVar) then
     CurrentThreadVar := TExternalThread.Create;
   Result := CurrentThreadVar;


 From within the TThread object, simply using Self seems more 
appropriate unless there is a chance that the same TThread instance is 
used for multiple OS-Threads. I don't know if/how this is possible.

 From "outside" I feel that AnyThread.GetCurrentThread does not make 
much senses.

When doing "TThread.GetCurrentThread" as a class function I think I 
should get "self" of same when I am in the code that is called from 
"Execute" of some TThread instance. I  don't see what I want to see when 
I'm not.

The code seems to try to avoid the case that a no TThread instance when  
GetCurrentThread is called as a a class function. I don't know if/how 
this is sensible.

Using CurrentThread only seems sensible within the the code of a 
component that has been called by the code of a TThread instance. But 
here using an appropriate back-link property can easily be used to avoid 
accessing the threadvar. (or using  CurrentThread once to set a 
property  and then just accessing same.) But this of course needs to be 
done in user code and the RTL can't force it.

-Michael