[Lazarus] Large program size - 1.8 MB for empty GUI project (uses clause in initialization vs implementation?)

[Florian Klaempfl]

Alexey S. Smirnov schrieb:
> Martin Friebe пишет:
>> Is this documented somewhere? I can't follow the logic anyway, the scope 
>> how much my code uses of another unit can not be predicted, simply by 
>> where I include the other code?
>>
>> Actually, I do believe I have seen examples where code form units used 
>> in the interface was successfully smart-linked.
>>
>> However there is a differentiation what can be smart linked and what 
>> not. If a class has RTTI information, then methods from it can not be 
>> removed by smart-linking. Classes with RTTI (afaik) are either included 
>> as a whole or not at all. (And that make sense, because RTTI allows to 
>> access any method by finding it from a resource or literal string; which 
>> are both not parsed by the compiler, and therefore not determinable)
>>
>> Best Regards
>> Martin
>>
>>   
> 
> May the problem will become understandable, if we will do a little
> experiment. So. Let's test the Interface/Implementation Uses sections of
> /lazarus/lcl/graphics.pp. This section for Lazarus 0.9.26 was that:
> |interface
> uses
>   SysUtils, Math, Types, Classes, Contnrs, FPCAdds,
>   FileUtil,
>   FPImgCmn, FPImage, FPCanvas,
>   FPReadPNG, FPWritePNG, PNGComn,  // png support
>   FPReadBMP, FPWriteBMP,   // bmp support
>   FPReadPNM, FPWritePNM,   // png support
>   FPReadJpeg, FPWriteJpeg, // jpg support
>   IntfGraphics,
>   AvgLvlTree,
>   LCLStrConsts, LCLType, LCLProc, LMessages, LCLIntf, LResources,
> LCLResCache,
>   GraphType, IcnsTypes, GraphMath, InterfaceBase, WSReferences;|
> |
> implementation
> uses
>   SyncObjs;|
> 
> It was cleanup by me and now looks like that:
> |Interface
> uses
>   SysUtils, Types,   Classes,
>   FPImgCmn, FPImage, FPCanvas,
>   FPReadJpeg,        FPWriteJpeg, // jpg support
>   IntfGraphics,      AvgLvlTree,
>   LCLType,   LMessages, LResources,LCLResCache,
>   GraphType, IcnsTypes, GraphMath, InterfaceBase, WSReferences;|
> 
> 
> |implementation
> uses
>  {FPReadPNG,} FPWritePNG,    PNGComn,  // png support
>  {FPReadBMP,} FPWriteBMP,   // bmp support
>  FPReadPNM,   FPWritePNM,   // png support
>  LCLStrConsts,LCLProc,LCLIntf,
>  FileUtil, FPCAdds, Math,
>  SyncObjs;
> 
> |So, previously we have 33 Units mentioned in Interface section and 1 in
> Implementation section. After cleanup we have 19 Units in Interface
> section and 12 in Implementation. 3 Units from Interface section was
> completely removed. ;)
> 
> Both Lazarus and all connected apps and projects are working fine with
> this cleanup.  And if you do the same thing - you will see that that
> size of Lazarus will be 15-20 KB less. May be - because of such
> optimization, may be - because of removing unused units from *Interface*
> section....

This could be simply the influence of a different memory layout of the exe.