Hello

I am just looking into this D language mostly just for fun, but seem to be unable to make a working DLL in D. I try to follow the instructions on the web side, but with no progress.

I have copied the dll.d (where the dllmain is) and then i have a transform_d.d
file looking like:

import std.math;

export void transform(double *x, double *y, double theta)
{
double c;
double s;
double x_tmp;

x_tmp = *x;
c = cos(theta);
s = sin(theta);
*x = x_tmp*c + *y*s;
*y = *y*c - x_tmp*s;
}


and a .def file looking like
LIBRARY "transform_d.dll"
DESCRIPTION 'DLL written in D'

EXETYPE NT
CODE PRELOAD DISCARDABLE
DATA PRELOAD SINGLE

EXPORTS
transform @2


To compile i use the command:
dmd -oftransform_d.dll transform_d.d dll.d transform_d.def

The compilation seem to go ok, but with the linker (which start automatically) i get the error message:

OPTLINK (R) for Win32  Release 7.50B1
Copyright (C) Digital Mars 1989 - 2001  All Rights Reserved

OPTLINK : Error 180: No Match Found for Export/ENTRY -  : transform OPTLINK : Error 81: Cannot EXPORT : transform
--- errorlevel 2


What am i doing wrong?

thanks

bsving wrote:
> I have copied the dll.d (where the dllmain is) and then i have a transform_d.d
> file looking like:
> 
> import std.math;
> 
> export void transform(double *x, double *y, double theta)
> {
> double c;
> double s;
> double x_tmp;
> 
> x_tmp = *x;
> c = cos(theta);
> s = sin(theta);
> *x = x_tmp*c + *y*s;
> *y = *y*c - x_tmp*s;
> }
[...]
> What am i doing wrong?
> 
> thanks

Try declaring transform as extern (C), i.e.:

export extern (C)
void transform(double *x, double *y, double theta) {
    // ...
}

-Kirk McDonald

In article <e55f2s$rr7$1@digitaldaemon.com>, Kirk McDonald says...
>
>>
>Try declaring transform as extern (C), i.e.:
>
>export extern (C)
>void transform(double *x, double *y, double theta) {
>     // ...
>}
>
>-Kirk McDonald

WOW, thanks. it works like a charm. Just for the fun of it I was investigating if it was possible to write D DLLs to be used in LabVIEW, and yes it works. But why do i need this extern (C)? the web site at Digitalmars says nothing about that.

bsving schreef:
> In article <e55f2s$rr7$1@digitaldaemon.com>, Kirk McDonald says...
>> Try declaring transform as extern (C), i.e.:
>>
>> export extern (C)
>> void transform(double *x, double *y, double theta) {
>>     // ...
>> }
>>
>> -Kirk McDonald
> 
> WOW, thanks. it works like a charm. Just for the fun of it I was investigating
> if it was possible to write D DLLs to be used in LabVIEW, and yes it works. But
> why do i need this extern (C)? the web site at Digitalmars says nothing about
> that.
> 
> 

Hello Kirk,

D normally mangles the names, into quite difficult to read object-file labels. So that you are able to do overloading, and having the same name in different modules. So this becomes possible:

module test1;

void transform(double *x);

module test2;

void transform(int[] y);
void transform(int[] y, int[] z);


Using the extern(C) directive eliminates the name mangling, making the object-file label looking like:

_transform

just as it would be in C

Regards,
Sjoerd