[fpc-pascal] Custom NewInstance allocator

[Hairy Pixels]

Thanks it's working now. The docs at https://www.freepascal.org/docs-html/rtl/system/tobject.newinstance.html confused me also. It says:

" If the memory was allocated, the class will be initialized by a call to InitInstance"

The text "will be" is what confused me. This implies to me it will be done by Object somewhere higher up in the chain. It should read:

"If memory was allocated it must be initialized by a call to InitInstance"

> On Jun 4, 2024, at 7:06 PM, Sven Barth via fpc-pascal <fpc-pascal at lists.freepascal.org> wrote:
> 
> Hairy Pixels via fpc-pascal <fpc-pascal at lists.freepascal.org> schrieb am Di., 4. Juni 2024, 10:54:
> In the manual it at https://www.freepascal.org/docs-html/ref/refse38.html it says "Calling the constructor will provoke a call to the virtual class method NewInstance, which, in its default implementation, calls GetMem, to allocate enough space to hold the class instance data, and then zeroes out the memory."
> 
> I'm trying this like below but it crashes. Is this correct? The fact NewInstance returns TObject instead of Pointer doesn't make sense to me and suggests this isn't correct.
> 
>   class function TDataObject.NewInstance: TObject;
>   begin
>     result := TObject(GetMem(InstanceSize));
>   end;
> 
> You also need to call TObject.InitInstance() on the allocated memory (that should probably be mentioned in the documentation...). 
> 
> Regards, 
> Sven 
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Regards,
Ryan Joseph