CallWindowProc() 生成错误 5（访问被拒绝）

Question

I'm trying to resolve error, that I get with GetLastError() during execution of CallWindowProc . The code is as follows:

static LRESULT CALLBACK editSubProc(HWND h, UINT m, WPARAM w, LPARAM l)
{
//some implementation
//GetLastError() returns 0 here
CallWindowProc(edit_proc,h,m,w,l);
}

Creation of window looks like below:

HWND ch=CreateWindowEx(style,"Edit","",dwstyle,l,t,r-l,b-t,hwnd,0,hInst,0);
edit_proc=(WNDPROC)GetWindowLongPtr(ch,GWLP_WNDPROC);
SetWindowLongPtr(ch,GWLP_WNDPROC,(LONG_PTR)editSubProc);

Now, the scenario is, that main loop calls IsDialogMessage(...) , which invokes editSubProc , which,through CallWindowProc , again invokes editSubProc . On the beggining of second invokation of editSubProc , GetLastError returns 5. Everything is invoked from the same thread. What could be the reason of such behavior?

Answer 1

GetLastError() returns the last error that happened (it even says so in the name!).

So the last error that happened was "access denied".

When did it happen? No clue. Was it supposed to happen? No idea. Is it a problem? Probably not. There are lots of reasons why access might be denied to something , and perhaps some part of the Windows OS just wanted to see whether it had access to something.

You should call GetLastError when you get an error and the documentation tells you to call it to get the error code . Otherwise you just get whatever the last error that happened was, which might be a completely different part of the program, maybe where there was supposed to be an error. You're making up imaginary problems, where none exist.