hi,

why is it that one can not create a class with the following:

module A
extern (Windows):
uint  P_Start(char * pParam);
void  P_Stop();

module A
import A;

class XXX {
public:
  this() {}
  uint start(char *yy) {
    return  P_Start(yy);
  }
  void start(char *yy) {
    P_Stop();
  }
}


module C

 XXX tester = new XXX();


it will always generate an error during compilation:

      non-constant expression

when i try to do that in a function, then i will get an exception.

sorry, it should be


module A
extern (Windows):
uint  P_Start(char * pParam);
void  P_Stop();

module B
import A;

class XXX {
public:
  this() {}
  uint start(char *yy) {
    return  P_Start(yy);
  }
  void start(char *yy) {
    P_Stop();
  }
}


module C
import B;

XXX tester = new XXX();

newbie wrote:
> module C
> 
>  XXX tester = new XXX();
> 
> 
> it will always generate an error during compilation:
> 
>       non-constant expression
> 
> when i try to do that in a function, then i will get an exception.

You can only use constant expressions as initializers for global variables, so dynamic memory allocation is disallowed. To do what you want, use:
---
module C;

XXX tester;

static this() {
    tester = new XXX();
}
---

Frits van Bommel Wrote:

> newbie wrote:
> > module C
> > 
> >  XXX tester = new XXX();
> > 
> > 
> > it will always generate an error during compilation:
> > 
> >       non-constant expression
> > 
> > when i try to do that in a function, then i will get an exception.
> 
> You can only use constant expressions as initializers for global variables, so dynamic memory allocation is disallowed. To do what you want, use:
> ---
> module C;
> 
> XXX tester;
> 
> static this() {
>      tester = new XXX();
> }
> ---

thank you for the reply.

it will compile, but it will fail with an exception.
that will also happen if i declare the variable in a function and than try to do my new.

void testers() {
	  XXX tester = new XXX(); <---- exception
	  tester.Stop();
}

could it be, that the extern(Windows) is a problem?

Frits van Bommel Wrote:

> newbie wrote:
> > module C
> > 
> >  XXX tester = new XXX();
> > 
> > 
> > it will always generate an error during compilation:
> > 
> >       non-constant expression
> > 
> > when i try to do that in a function, then i will get an exception.
> 
> You can only use constant expressions as initializers for global variables, so dynamic memory allocation is disallowed. To do what you want, use:
> ---
> module C;
> 
> XXX tester;
> 
> static this() {
>      tester = new XXX();
> }
> ---
it is seeminglx not possible to call d functions or initialize d classes from a function that is decorated with extern(Windows)

extern (Windows) int WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
	testery();
    DialogBox(hInstance, MAKEINTRESOURCE(IDD_DIALOG_MAIN), null, &Dialog_Main);
    return 0;
}


void testery() {
	  XXX testerx = new XXX;
	  testerx.Stop();
}


how does one call a D function or do a XXX testerx = new XXX; in such a function?

newbie wrote:
> Frits van Bommel Wrote:
> 
>> newbie wrote:
>>> module C
>>>
>>>  XXX tester = new XXX();
>>>
>>>
>>> it will always generate an error during compilation:
>>>
>>>       non-constant expression
>>>
>>> when i try to do that in a function, then i will get an exception.
>> You can only use constant expressions as initializers for global variables, so dynamic memory allocation is disallowed. To do what you want, use:
>> ---
>> module C;
>>
>> XXX tester;
>>
>> static this() {
>>      tester = new XXX();
>> }
>> ---
> it is seeminglx not possible to call d functions or initialize d classes from a function that is decorated with extern(Windows)
> 
> extern (Windows) int WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
> 	testery();
>     DialogBox(hInstance, MAKEINTRESOURCE(IDD_DIALOG_MAIN), null, &Dialog_Main);
>     return 0;
> }
> 
> 
> void testery() {
> 	  XXX testerx = new XXX;
> 	  testerx.Stop();
> }
> 
> 
> how does one call a D function or do a XXX testerx = new XXX; in such a function?
> 
> 

Wait; you're calling this from WinMain?

The code you just supplied will not work because you haven't initialised the garbage collector, nor run module ctors, nor run unittests.  See http://digitalmars.com/d/windows.html for an example of what your WinMain should look like.

	-- Daniel

Daniel Keep Wrote:

> 
> 
> newbie wrote:
> > Frits van Bommel Wrote:
> > 
> >> newbie wrote:
> >>> module C
> >>>
> >>>  XXX tester = new XXX();
> >>>
> >>>
> >>> it will always generate an error during compilation:
> >>>
> >>>       non-constant expression
> >>>
> >>> when i try to do that in a function, then i will get an exception.
> >> You can only use constant expressions as initializers for global variables, so dynamic memory allocation is disallowed. To do what you want, use:
> >> ---
> >> module C;
> >>
> >> XXX tester;
> >>
> >> static this() {
> >>      tester = new XXX();
> >> }
> >> ---
> > it is seeminglx not possible to call d functions or initialize d classes from a function that is decorated with extern(Windows)
> > 
> > extern (Windows) int WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow) {
> > 	testery();
> >     DialogBox(hInstance, MAKEINTRESOURCE(IDD_DIALOG_MAIN), null, &Dialog_Main);
> >     return 0;
> > }
> > 
> > 
> > void testery() {
> > 	  XXX testerx = new XXX;
> > 	  testerx.Stop();
> > }
> > 
> > 
> > how does one call a D function or do a XXX testerx = new XXX; in such a function?
> > 
> > 
> 
> Wait; you're calling this from WinMain?
> 
> The code you just supplied will not work because you haven't initialised the garbage collector, nor run module ctors, nor run unittests.  See http://digitalmars.com/d/windows.html for an example of what your WinMain should look like.
> 
> 	-- Daniel
that was the wright thing to do - thank you all so much.

"newbie" <newbie@nospam.com> wrote in message news:f8n64d$1bev$1@digitalmars.com...
> hi,
>
> why is it that one can not create a class with the following:
>
> module A
> extern (Windows):

You're missing the semicolon after the module name.

<snip>
> it will always generate an error during compilation:
>
>      non-constant expression

On what compiler version are you getting that?  Please post compiler messages in full.

Stewart.