Can I override a globally defined API in a C++/MFC project?

Question

I need to ensure that message boxes are shown only if my app is running in an interactive desktop. So I was thinking, can I override ::MessageBox and AfxMessageBox with my own implementation (from a C++/MFC project, compiled with VS 2008)?

PS. I do not need global hooks. This needs to work only from my app's code. For instance, if somewhere in the code I have ::MessageBox(...); it should let me call my own method instead of linking to the system API.

Answer 1

The default MessageBox (actually MessageBoxA or MessageBoxW) is defined as an export, so unfortunately you can't just define a local version to link in first. If you have access to all the source that uses MessageBox it's simple to redefine the MessageBox macro after including windows.h though:

#include <windows.h>
#undef MessageBox
#define MessageBox MyMessageBox

If you have 3rd party binaries or something where you don't compile the code this wouldn't work of course.

Answer 2

如果使用MFC，则可以覆盖CWinApp :: DoMessageBox函数。