DLLs and C

Firecore

114 100+

Does anyone know how to call DLL functions using C?
eg. PlaySound
MessageBox

Jul 16 '07 #1

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1974

weaknessforcats

9,208

Expert Mod 8TB

1) Call LoadLibrary() to load the DLL.
2) Call GetProcAddress() to get the address of your function from the DLL. You will need the HMODULE from LoadLibrary() and a string with the function name. This address will be returned as a FARPROC.
3) Declare a function pointer of the correct arguments and return type.
4) Assign the FARPROC to this function pointer using a typecast.
5) Call your function using the pointer.
6) Call FreeLibrary() when you are done with the DLL and want to unload it. Use the HMODULE from LoadLibrary()

Jul 16 '07 #2

Firecore

114

100+

Could you please explain a bit more?

Jul 17 '07 #3

JosAH

11,448

Expert 8TB

Could you please explain a bit more?

I don't even speak Microsoft C, and even I could understand what WFC's
explanation is all about:

Expand|Select|Wrap|Line Numbers

 
// 1) Call LoadLibrary() to load the DLL.

HMODULE myLib= LoadLibrary("myDLL" /* maybe more params here */);
 
// 2) Call GetProcAddress() to get the address of your function from the DLL. 

// You will need the HMODULE from LoadLibrary() and a string with the function 

// name. This address will be returned as a FARPROC.

FARPROC myAddr= LoadLibrary(myLib, "myFunc");
 
// 3) Declare a function pointer of the correct arguments and return type.

typedef int (*foo_t)(double); // or whatever
 
// 4) Assign the FARPROC to this function pointer using a typecast.

foo_t foo= (foo_t)myAddr;
 
// 5) Call your function using the pointer.

printf("%d\n", foo(42.54);
 
// 6) Call FreeLibrary() when you are done with the DLL and want to unload it. 

// Use the HMODULE from LoadLibrary()

FreeLibrary(myLib);

kind regards,

Jos

Jul 17 '07 #4

Firecore

114

100+

I don't even speak Microsoft C, and even I could understand what WFC's
explanation is all about:

Oh Ok..............
Maybe you coulkd but I could not.
I guess I need a lot more work eh?
And is Microsoft C the same as Turbo C from Borland?

Jul 17 '07 #5

JosAH

11,448

Expert 8TB

Oh Ok..............
Maybe you coulkd but I could not.
I guess I need a lot more work eh?
And is Microsoft C the same as Turbo C from Borland?

I guess not; that LoadLibrary() function is a Microsoft-ism as far as I know; If the
Borland folks are a bit clever they'd use the POSIX standard dlopen(), dlclose()
and dlsym() method names.

kind regards,

Jos

Jul 17 '07 #6

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