Category : C++ Source Code
Archive   : C_ALL.ZIP
Filename : TI866.ASC

PRODUCT : C++ NUMBER : 866
VERSION : All
OS : WIN
DATE : August 12, 1992 PAGE : 1/1

TITLE : Using The Windows API Function MakeProcInstance




I keep getting a type mismatch error from the compiler when I
pass my function pointer to MakeProcInstance, and a type mismatch
error when I assign my function's return value to another
function pointer. Why?

Unless two functions take the same parameters, they are
considered to be of different types. Thus, if I declare a
DlgProc like so:

int FAR PASCAL _export DlgProc(HWND, WORD, WORD, DWORD);

I will get a type mismatch when I do:

MakeProcInstance(DlgProc, hInstance);

because MakeProcInstance expects a FARPROC for its first
parameter, which is declared to be a

typedef int (FAR PASCAL *FARPROC)();

To suppress this error, do this:

MakeProcInstance((FARPROC)DlgProc, hInstance);

That is typecast the function pointer you're passing to
MakeProcInstance to be the type it expects. Similarly, since
MakeProcInstance returns a FARPROC, you will get an error if you
assign its return value into other than a FARPROC. You would
need to either make the variable your assigning
MakeProcInstance's return value into a FARPROC, or typecast the
return value to the type of your variable.

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