how to create and use dll in C

Question

hi friend, how to create and use dynamic library in c language? thank very much.

Vulpes · Answer

Here's a very simple example. Go into the Visual Studio command prompt, type notepad mydll.c, enter the following code and save it: #include __declspec(dllexport) void myFunction() { printf ("Hello from MyDll!
"); } Now type the following at the command prompt to compile this into a .dll (notice that a .lib is created at the same time though we won't need this): cl /LD mydll.c Next type notepad myexe.c, enter the following code and save it: #include typedef void (*MyFunc)(void); /* define function pointer to call function in dll */ int main() { MyFunc myFunc; /* declare variable of function pointer type */ HINSTANCE hInst = LoadLibrary("mydll.dll"); /* load dll and get its handle */ if (hInst) /* if handle is not null */ { myFunc = (MyFunc)GetProcAddress(hInst, "myFunction"); /* get function address */ if(myFunc) myFunc(); // if pointer is not null, call function via the pointer */ printf("And hello also from MyExe!"); FreeLibrary(hInst); /* unload dll */ } else { printf("Unable to load dll"); } return 0; } Now, type the following at the command prompt to compile this into an .exe which calls the function in the .dll at runtime: cl myexe.c Finally type : myexe to run it and you should see the following output: Hello from MyDll! And hello also from MyExe!

Vulpes · Answer

It's more than 10 years since I last used Visual Studio 6.0 and I can't remember now how to get into the command prompt. If you start VS by clicking on the Start Button and then selecting it from 'All Programs', then there may be an additional 'Visual Studio Command Prompt' option like there is in the current version. Otherwise, it might be a menu option within VS itself - I just can't remember, I'm afraid :( Incidentally, you can download the free VC++ 2010 Express edition from the following link if you want a more up to date edition. What I've done above definitely works in this: http://www.microsoft.com/visualstudio/en-gb/express

Ken H · Answer

VC++ 6 project in the version of Visual Studio where can call command line. thanks

Vulpes · Answer

I can't open a VC++ 6 project in the version of Visual Studio I have (2010) but what I can tell you is that the dll and exe should be compiled to entirely separate projects which you don't appear to be doing at present. It would really be better to do it from the command line first before trying to get it to work in VC++ 6 which is an exercise in itself :)

Ken H · Answer

hi Vulpes, I try to follow your code, but i can not achieve, and why? my project in Annex.

how to create and use dll in C

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