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How Do I Create And Use A Dll?

I am use to writing command line based C code. I want to retain the code in proc1 (except for printf, although it could become a message box) but replace main with a simple GUI using MS VC. How do I make proc1 into a DLL? And how do I write C++ code to use that DLL?
extern void proc1(char *);
main()
{
char mystr[128]=”output.txt”;
char *str1;
str1=&mystr[0];
proc1(str1);
}
#include
#include
void proc1(char *instr)
{
FILE *outptr;
outptr=fopen(instr,”w”);
if(outptr==NULL)
{
printf(“Could NOT create file (%s)\n”,instr);
exit(0);
}
else
{
fprintf(outptr,”Add some text\n”);
fprintf(outptr,”This is the file: %s\n”,instr);
}
printf(“File written: [%s]\n”,instr);
}

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This entry was posted on Sunday, December 6th, 2009 at 11:40 am and is filed under dll errors. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

One Response to “How Do I Create And Use A Dll?”

  1. Soheil says:
    December 6, 2009 at 11:40 am

    It is a simple process. Just create a DLL VC++ project, and expose your intended function with a __declspec modifier as
    extern “C” __declspec(dllimport) void proc1(char* instr);
    for user code and
    extern “C” __declspec(dllexport) void proc1(char* instr);
    for the provider code.
    To simplify this process you could make a common header file proc1.h having
    #ifdef EXPORTING
    extern “C” __declspec(dllexport) void proc1(char* instr);
    #else
    extern “C” __declspec(dllimport) void proc1(char* instr);
    #endif
    for your main file, simply include this header
    #include “proc1.h”
    for your proc1.c use an extra #define:
    #define EXPORTING
    #include “proc1.h”
    Good luck

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