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From: Larry on 12 Feb 2010 11:56
Hi,

I would like to create custom macro (and methods) in order to deal with
message sent from the menu, so far I have coded the following:

#define STRICT
#include <windows.h>
#include <windowsx.h>

#define IDM_BLOCK 800

// Declare Custom HANDLE MSG //
#define HANDLE_IDM_BLOCK(hwnd, wParam, lParam, fn) \
((fn)(hwnd), 0L)

#define FORWARD_IDM_BLOCK(hwnd, fn) \
(void)(fn)((hwnd), IDM_BLOCK, 0L, 0L)
///////////////////////////////

// Default
void Cls_OnDestroy(HWND hwnd);
void Cls_OnCommand(HWND hwnd, int id, HWND hwndCtl, UINT codeNotify);
BOOL Cls_OnCreate(HWND hwnd, LPCREATESTRUCT lpCreateStruct);

// Custom
void Cls_OnMenuBlock(HWND hwnd);

LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM
lParam)
{
__try
{
switch (message)
{
HANDLE_MSG (hWnd, WM_CREATE, Cls_OnCreate);
HANDLE_MSG (hWnd, WM_COMMAND, Cls_OnCommand);
HANDLE_MSG (hWnd, WM_DESTROY, Cls_OnDestroy);
}
}
__except(EXCEPTION_EXECUTE_HANDLER) {}

return DefWindowProc(hWnd, message, wParam, lParam);
}

void Cls_OnCommand(HWND hWnd, int id, HWND hwndCtl, UINT codeNotify)
{
__try
{
switch (id)
{
HANDLE_MSG (hWnd, IDM_BLOCK, Cls_OnMenuBlock);
}
}
__except(EXCEPTION_EXECUTE_HANDLER) {}
}

void Cls_OnMenuBlock(HWND hwnd)
{

}

Now, when I run the code I get this error: error C2562: 'Cls_OnCommand' :
'void' function returning a value

I don't see that function returns any value as opposite to the error fired
by the compiler...

what am I doing wrong? I just need functions like this: Cls_OnMenuBlock(HWND
hwnd); to take along only the HWND

thanks

From: Igor Tandetnik on 12 Feb 2010 12:23
Larry <dontmewithme(a)got.it> wrote:
> // Declare Custom HANDLE MSG //
> #define HANDLE_IDM_BLOCK(hwnd, wParam, lParam, fn) \
> ((fn)(hwnd), 0L)
>
> void Cls_OnCommand(HWND hWnd, int id, HWND hwndCtl, UINT codeNotify)
> {
> __try
> {
> switch (id)
> {
> HANDLE_MSG (hWnd, IDM_BLOCK, Cls_OnMenuBlock);
> }
> }
> __except(EXCEPTION_EXECUTE_HANDLER) {}
> }
>
> Now, when I run the code I get this error: error C2562:
> 'Cls_OnCommand' : 'void' function returning a value

HANDLE_MSG is defined this way in windowsx.h:

#define HANDLE_MSG(hwnd, message, fn) \
case (message): return HANDLE_##message((hwnd), (wParam), (lParam), (fn))

Thus, your function, despite being declared void, contains "return some_expression;" statement.

> I don't see that function returns any value as opposite to the error
> fired by the compiler...

HANDLE_IDM_BLOCK expands to (something, 0L). This is an expression with a value of 0L. So basically you are doing

case IDM_BLOCK:
something;
return 0L;

This return statement is illegal in a function with a return type of void.
--
With best wishes,
Igor Tandetnik

With sufficient thrust, pigs fly just fine. However, this is not necessarily a good idea. It is hard to be sure where they are going to land, and it could be dangerous sitting under them as they fly overhead. -- RFC 1925

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