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digitalmars.D - Linking D DLL to C

reply Kirk McDonald <kirklin.mcdonald gmail.com> writes:
I am about 50% certain I am missing something obvious. I'm playing with 
DLLs in D, and following the example here:

http://digitalmars.com/d/dll.html

The end result of this tutorial are some D source files:

dll.d
mydll.d
mydll2.d
test.d

and also a .def file (mydll.def), a .lib file (mydll.lib), and of course 
the .dll (mydll.dll). The command

C:>dmd test.d mydll.lib

goes fine, and the resultant executable works fine.

Fine.

Now I want to call this DLL from a C program. First, I re-wrote mydll.d 
and mydll2.d and recompiled the DLL and the test executable:

[mydll.d]
export extern(C) void dllprint();

[mydll2.d]
module mydll;
export extern(C)
void dllprint() { printf("hello dll world\n"); }

The original .exe still works. Fine. Then I wrote a C header file and a 
test2.c:

[mydll.h]
__declspec(dllimport) void dllprint(void);

[test2.c]
#include "mydll.h"

int main(int argc, char* argv[]) {
     dllprint();
     return 0;
}

This does not work. I am using MinGW 3.4.2. The following command works:

C:>gcc -c test2.c

test2.o is generated without issue. However:

C:>gcc -L. -lmydll test2.o
./mydll.dll: file not recognized: File format not recognized
collect2: ld returned 1 exit status

The linker fails. Again, I'm pretty sure I'm missing something obvious. 
Any help?

-Kirk McDonald
May 23 2006
parent reply BCS <BCS pathlink.com> writes:
Kirk McDonald wrote:
[...]

 
 This does not work. I am using MinGW 3.4.2. The following command works:
 
 C:>gcc -c test2.c
 
 test2.o is generated without issue. However:
 
 C:>gcc -L. -lmydll test2.o
 ./mydll.dll: file not recognized: File format not recognized
 collect2: ld returned 1 exit status
 
 The linker fails. Again, I'm pretty sure I'm missing something obvious. 
 Any help?
 
 -Kirk McDonald



First of all I'd try the using dmc/optlink instead of gcc. I haven't 
tried this but dmd on win does have some issues with object/lib file 
compatibility (at least with VS).
May 23 2006
parent reply Kirk McDonald <kirklin.mcdonald gmail.com> writes:
BCS wrote:

 First of all I'd try the using dmc/optlink instead of gcc. I haven't 
 tried this but dmd on win does have some issues with object/lib file 
 compatibility (at least with VS).



Interesting. That did it:

C:>dmc -c test2.c

C:>dmc test2.obj mydll.lib
link test2,,,mydll+user32+kernel32/noi;

C:>test2
hello dll world

Are there any plans to fix this? Is this perceived as a serious problem?

-Kirk McDonald
May 23 2006
next sibling parent "d" <d nomail.com> writes:
"Kirk McDonald" <kirklin.mcdonald gmail.com> wrote in message
news:e506jv$9gv$1 digitaldaemon.com...

 Are there any plans to fix this? Is this perceived as a serious problem?



I would actually put this down to gcc not recognising the .lib format you
generated. Have a look at the mingw/cygwin gcc specs. I'm sure you have to
generate gcc specific .a files, or at least gcc specific .lib files from the
.def file. IIRC there is a tutorial on the Net about creating dll's with
Mingw, might be worth looking at that to see what is going on.

M
Jun 01 2006
prev sibling parent "Unknown W. Brackets" <unknown simplemachines.org> writes:
If you want a dll, and you're staticly linking it, you have to create an 
import library from the dll...

To link dynamically, you'll typically use LoadLibrary(), etc. at least 
on Windows.

-[Unknown]



 BCS wrote:

 First of all I'd try the using dmc/optlink instead of gcc. I haven't 
 tried this but dmd on win does have some issues with object/lib file 
 compatibility (at least with VS).



 Interesting. That did it:
 
 C:>dmc -c test2.c
 
 C:>dmc test2.obj mydll.lib
 link test2,,,mydll+user32+kernel32/noi;
 
 C:>test2
 hello dll world
 
 Are there any plans to fix this? Is this perceived as a serious problem?
 
 -Kirk McDonald
Jun 01 2006