Re: cast fails for classes from windows dll

[Benjamin Thaut via Digitalmars-d-learn]

On Tuesday, 12 January 2016 at 19:00:26 UTC, Andre wrote:

Hi,

I am not sure, whether this is a current limitation of the 
windows dll functionality of D

or I am doing s.th. which will not work.

I have developed in D a windows DLL which creates class 
instances by passing the name (using object.factory method).


In another D application I am using this DLL. My issue is, that 
the cast fails, although

typeid(bar).name shows the correct name .


module main;

// these classes are in a seperate module
// used for the dll & for this application
export class Foo {}
export class Bar : Foo {}
class Baz : Bar {}

void main()
{
// this method calls the dll and returns Foo
Foo c = dllCreateClass("main.Baz");

// no failure
assert( typeid(c).name == "main.Baz");

// > fails
if (auto myBar = cast(Bar) c){}
}

Kind regards
André


Thats a limitation of the current dll functionality. The type 
info of the class gets duplciated into both your executable and 
the dll and thus the cast fails. Until D properly supports Dlls 
on windows this is going to stay this way. Currently only a C 
like interface across dll boundaries is possible.

cast fails for classes from windows dll

[Andre via Digitalmars-d-learn]

Hi,

I am not sure, whether this is a current limitation of the 
windows dll functionality of D

or I am doing s.th. which will not work.

I have developed in D a windows DLL which creates class instances 
by passing the name (using object.factory method).


In another D application I am using this DLL. My issue is, that 
the cast fails, although

typeid(bar).name shows the correct name .


module main;

// these classes are in a seperate module
// used for the dll & for this application
export class Foo {}
export class Bar : Foo {}
class Baz : Bar {}

void main()
{
// this method calls the dll and returns Foo
Foo c = dllCreateClass("main.Baz");

// no failure
assert( typeid(c).name == "main.Baz");

// > fails
if (auto myBar = cast(Bar) c){}
}

Kind regards
André