[fpc-pascal] units order (was using oldlinux )

Alain Vitry alain.vitry at gmail.com
Tue Jun 14 10:45:26 CEST 2005

Thanks for the answer.

But is that by design ?

Let' look at this case (not the best design, but big legacy):

File common.pas:
uses  StandardFile, MacWindows;
var MaPict: array[WPictWind_1..WPictWind_3] of PicHandle;

File utils.pas:
uses commons, MacWindows, SegLoad, Quickdraw, StandardFile;
var PictRect: Rect;
DrawPicture(PictArray[i], PictRect);

Utils.pas(316,29) Error: Incompatible type for arg no. 1: Got 
"MACWINDOWS.PicHandle", expected "STANDARDFILE.PicHandle"

I know about unit propagation. PicHandle is first defined in 
MacWindows, then used in standardfile.
The best solution I've found is to suffle units around, altough I find 
this approach inelegant.
Renaming every occurence of some types is a better solution, altough 
very intrusive.

Shouldn't type A defined in unit X be fixed whether units Y, Z who also 
use it are included or not in my program ?
Also when unit Y defines a procedure with type A (from unit X) as 
parameter, shouldn't type A still refer to the type A as defined in 
unit X, and not become some types like Y.A ?

It is unclear to me, why this problem occur in the first place (In this 
case there is no re-definition of the types, as for oldlinux)

Kind regards,

Le 14 juin 05, à 10:07, Vincent Snijders a écrit :

> Alain Vitry wrote:
>> Le 14 juin 05, à 09:46, Michael Van Canneyt a écrit :
>>> You must switch the order of the units, because you get the 
>>> 'oldlinux' types which
>>> you try to use in 'baseunix' functions.
>> This unit order trick is a bit of a wizardery to me. It quickly get 
>> very messy in a large enough program to swap units order until you 
>> get the one which doesn't break.
>> In the sw I'm porting, almost every single UPI type is re-defined in 
>> many units, which makes FPC complain about types.
>> Am I missing some switches or some pascal features, with my kernel 
>> hacker mind ?
> You can also specify from which unit you want to use the 
> type/procedure/function/constant.
> Suppose both unit A and unit B declare a procedure DoIt;
> You could do something like this:
> program p;
> uses A, B;
> begin
>   A.DoIt; // calls DoIt in unit a
>   B.DoIt; // calss DoIt in unit b
> end;
> Vincent.
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> fpc-pascal maillist  -  fpc-pascal at lists.freepascal.org
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