Question

I attampted to write a Message Map following a sample in a book.

Here is my code:

typedef struct MsgMapEntry_t {  
    UINT nMessage;  
    LONG (*pFunc)(HWND, UINT, WPARAM, LPARAM);  
} MsgMapEntry_t;  

// Skip Lines  

LRESULT CALLBACK CyauShellWndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)  
{
    static MsgMapEntry_t OnMsgMap[]=  
    (  
        // TODO Register MsgFunc here  
        WM_DESTROY, ExitApplication  
    );  

Compile it, and the compiler gives out an error:

D:\Projects\cyau\cyau_pre3_20120225\cyau_main.cpp:116:15: warning: left operand of comma operator has no effect [-Wunused-value]
D:\Projects\cyau\cyau_pre3_20120225\cyau_main.cpp:117:2: error: initializer fails to determine size of ‘OnMsgMap’

So, How to correct it, please.

Answer 1

You need two pairs of curly braces (one for the array, one for the struct), instead of a single pair of parentheses.

static MsgMapEntry_t OnMsgMap[]= { // start the array
    // TODO Register MsgFunc here  
    { // start the struct
    WM_DESTROY, ExitApplication
    } // end the struct; more data can go here after ','
}; // end the array