LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
FILE *log;
switch(msg)
{
case WM_CREATE:
{
log = fopen("log.txt", "a");
fprintf (log, "Program started");
}
break;
case WM_CLOSE:
DestroyWindow(hwnd);
break;
case WM_DESTROY:
{
fprintf (log, "Program closed");
fclose (log);
PostQuitMessage(0);
}
break;
default:
return DefWindowProc(hwnd, msg, wParam, lParam);
}
return 0;
}
File rw and win32
Author
Coders,
I stumbled across something I don’t really understand. Let me just quickly present a bit of code:
Just a standard WinProc followed by a standard WinMain. For some reason when I close the window – apparently when it comes to the file manipulation lines the program crashes.
Any suggestions on what I am doing wrong?
Tons of thanks in advance.
Your FILE* log is inside the scope of the WndProc. For every message your WndProc receives a new FILE* log is created on the stack and discarded on leaving the function.
So on WM_DESTROY you're trying to write to an uninitialized FILE* handle.
Either have A) a global FILE* log somewhere, B) make it static FILE* log or C) have a logging class that takes care of the file handle and stays alive outside the WndProc function.
So on WM_DESTROY you're trying to write to an uninitialized FILE* handle.
Either have A) a global FILE* log somewhere, B) make it static FILE* log or C) have a logging class that takes care of the file handle and stays alive outside the WndProc function.
This topic is closed to new replies.
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