Overcoming "C4071 No Function Prototype Given" Warning

ID: Q69898

The information in this article applies to:

Microsoft Windows Software Development Kit (SDK) versions 3.0, 3.1

SYMPTOMS

Code that is compiled using the Microsoft C compiler's warning level 3 (/W3) or higher and that calls functions through FARPROC pointers causes the Microsoft C compiler to report warning C4071, "No Function Prototype Given."

CAUSE

Pointers to functions are commonly used when an application explicitly loads dynamic-link libraries (DLLs) through the Windows LoadLibrary function. Function pointers declared with FARPROC do not inherit function prototype information.

RESOLUTION

Modify the function pointers declarations to include function prototype information.

MORE INFORMATION

The following code sample uses the generic FARPROC far-pointer-to-function data type. Compiling the code with Microsoft C at warning level 3 or higher results in a C4071 warning:

FARPROC lpfnErrorProc;
lpfnErrorProc = GetProcAddress(hModule, MAKEINTRESOURCE(1));
(*lpfnErrorProc)(hWnd, (LPSTR)"Error Message");

However, the following code sample defines custom far-pointer-to- function data types which provide information about the function arguments. This code does not produce the warning:


   // typedef declarations
   typedef VOID FAR PASCAL FNERRORPROC(HWND, LPSTR);
   typedef FNERRORPROC FAR *LPFNERRORPROC;

   // variable declaration
   LPFNERRORPROC  lpfnErrorProc;

   // variable assignment and indirect function call
   lpfnErrorProc = GetProcAddress(hModule, MAKEINTRESOURCE(1));
   (*lpfnErrorProc)(hWnd, (LPSTR)"Error Message");

Additional query words: 3.00 3.10

Keywords : kb16bitonly
Version : WINDOWS:3.0,3.1
Platform : WINDOWS
Issue type :