Pelles C forum

C language => Beginner questions => Topic started by: Feierabend on April 08, 2008, 10:06:45 AM

Title: write my own dll using MS VC++ template
Post by: Feierabend on April 08, 2008, 10:06:45 AM

Hello,
I am new to Pelles C.

I have deep experiences with C under Unix plattforms,
but none with C under Win32.

Actually I try to create a dll file which shall contain a function mytest()
I'd like to call from several different exe files.
To do this I've got a Demo.h template which looks like this:


#ifndef DEMO_H
#define DEMO_H

typedef char bool;
struct DEMO_DATASTRUCT
{
    int year,month,day,starttime,endtime;
    bool plotme;
    bool ascii_been_here;
};

extern "C" double __declspec(dllexport) mytest(DEMO_DATASTRUCT *price_ptr,
    int currentptr, int *int_args, int num_int_args, double *double_args,
    int num_double_args, char **string_args, int num_string_args);

#endif

The according c-source Demo.c file has this content:

#include <windows.h>
#include "Demo.h"

//---------------------------------------------------------------------------

extern "C" double __declspec(dllexport) mytest(DEMO_DATASTRUCT *price_ptr,
    int currentptr, int *int_args, int num_int_args, double *double_args,
    int num_double_args, char **string_args, int num_string_args)
{
    /* well, this function actually does nothing usefull,
    however, it should compile without failure */
   
    return 0.4711;
}

#pragma argsused
BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fwdreason, LPVOID lpvReserved)
{
    return 1;
}


My question regarding Pelles C is,
how must this template be modified to compile it as a dll library.

I'd appreciate, if anyone could explain me this.

Thanks in advance
Christoph

Title: Re: write my own dll using MS VC++ template
Post by: TimoVJL on April 08, 2008, 08:04:42 PM

For example:
Demo.h

Code: [Select]

#ifndef DEMO_H
#define DEMO_H

typedef char bool;
typedef struct tagDEMO_DATASTRUCT
{
    int year,month,day,starttime,endtime;
    bool plotme;
    bool ascii_been_here;
} DEMO_DATASTRUCT;

#ifdef __cplusplus
extern "C"
{
#endif
double __declspec(dllexport) mytest(DEMO_DATASTRUCT *price_ptr,
    int currentptr, int *int_args, int num_int_args, double *double_args,
    int num_double_args, char **string_args, int num_string_args);
#ifdef __cplusplus
}
#endif
#endif
Demo.c

Code: [Select]

#define WIN32_LEAN_AND_MEAN
#include <windows.h>
#include "Demo.h"

//---------------------------------------------------------------------------

double __declspec(dllexport) mytest(DEMO_DATASTRUCT *price_ptr,
    int currentptr, int *int_args, int num_int_args, double *double_args,
    int num_double_args, char **string_args, int num_string_args)
{
    /* well, this function actually does nothing usefull,
    however, it should compile without failure */
   
    return 0.4711;
}

#pragma argsused
BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fwdreason, LPVOID lpvReserved)
{
    return 1;
}


Title: Re: write my own dll using MS VC++ template
Post by: Feierabend on April 09, 2008, 06:47:08 AM

Thank you very much.

The compiler also creates
C:\Programme\PellesC\Projects\demo\demo.exp
C:\Programme\PellesC\Projects\demo\demo.lib

What are these files good for?

Title: Re: write my own dll using MS VC++ template
Post by: Feierabend on April 09, 2008, 09:56:57 AM

And another question, please, too:

if I want to access a function residing in an other already finished dll,
how do I have to declare it within my Demo.c ?

I have a swe32.dll which has a function built in
which is called swe_date_conversion() for instance.

The function is defined as

Code: [Select]

int swe_date_conversion(
    int yyyy, int month, int day,
    double hour,
    double *tjd);

I want to call it in function mytest() as coded in Demo.c

Now mytest() looks like:

Code: [Select]

double __declspec(dllexport) mytest(DEMO_DATASTRUCT *price_ptr,
    int currentptr, int *int_args, int num_int_args, double *double_args,
    int num_double_args, char **string_args, int num_string_args)
{

    double tjd = 0.0;
    int vdate = swe_date_conversion(2008, 4, 9, 12.0, &tjd);

    return tjd;

}

Actually I get "POLINK: error: Unresolved external symbol '__imp__swe_date_conversion'."
I thinks it's a matter of declaration here.

Please can you show me how to declare the swe_date_conversion() correctly?

Title: Re: write my own dll using MS VC++ template
Post by: Stefan Pendl on April 09, 2008, 01:10:16 PM

Quote from: Feierabend on April 09, 2008, 09:56:57 AM

Actually I get "POLINK: error: Unresolved external symbol '__imp__swe_date_conversion'."
I thinks it's a matter of declaration here.

Please can you show me how to declare the swe_date_conversion() correctly?

Include the swe32.lib in the Linker options of the Project options for your project.