Changing the value that lParam points at

Question

I'm using Visual C++ /MFC and I'm sending a message as SendMessage(GetParent(hDlg) ,MY_MESSAGE , 0 , LPARAM(x) );

How could I change the value of x inside the hDlg parent callback function ?

For example if I send the message SendMessage(hWnd , WM_GETTEXT ,0 , LPARAM(buffer); the buffer is returned full of the text . How did the buffer changed it's value ?

You'll need `&x` if you want to change the variable's value. You don't need `&buffer`, a reference to a C array already automatically decays to a pointer to its first element. — Hans Passant, Jun 09 '15 at 13:27
Alright I know this ,but my question is how to change the value inside the callback . — Omar Natour, Jun 09 '15 at 14:00
Cast the lparam argument back to (whateverxmightbe*) and assign the value. — Hans Passant, Jun 09 '15 at 14:07

score 1 · Answer 1 · answered Jun 09 '15 at 13:16

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(buffer) is a pointer to some memory that has already been allocated. The WM_GETTEXT operation can use that pointer to put data into the allocated memory. You can do the same thing if your (x) variable is a pointer to some memory that has already been allocated.

answered Jun 09 '15 at 13:16

ScottMcP-MVP

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I need to know how to make the same – Omar Natour Jun 09 '15 at 13:49

Changing the value that lParam points at

1 Answers1