Peter,
That's a classic memory allocation/pointer question.
The memory is allocated by XtMalloc(). The result of the XtMalloc()
call is a pointer. You can keep as many copies of a pointer as you
like, this doesn't change the allocated memory.
The local variable (copy in the example below) is a temporary
storage; the widget field (mw->matrix.cells) is a more permanent
storage.
The allocated memory is freed in xbaeFreeCells(). To prevent
memory leaks from happening, xbaeFreeCells must be called prior
to widget destruction (before mw->matrix.cells looses its
permanent nature); or before overwriting mw->matrix.cells.
Hope this helps,
Danny
> "Yang, Peter" wrote:
>
> Would you please straight me out on following question? I was
> challenged by my friends here. And I can not provide a good answer to
> them. Thanks a bunch.
>
> IN the code "Create.c >> xbaeCopyCells(XbaeMatrixWidget mw)", it was
> noticed that the two dimension arrary "copy" is allocated , then
> assign the address to other variable. But the "copy" is not freed in
> this code.
>
> Is it freed at somewhere else ??
>
> See sample code below.
>
> xbaeCopyCells(XbaeMatrixWidget mw)
> {
> String **copy = NULL;
> int i, j;
> Boolean empty_row;
>
> xbaeObjectLock((Widget)mw);
>
> if (mw->matrix.rows && mw->matrix.columns)
> {
> /*
> * Malloc an array of row pointers
> */
> copy = (String **) XtMalloc(mw->matrix.rows * sizeof(String *));
> <<<<<??? Allocate memory ????
>
> ......
> ......< skip other code >
> ......
>
> mw->matrix.cells = copy; <<<<<<< assign
> memory location to someone else ????
>
>
> But who free it ?
>
> xbaeObjectUnlock((Widget)mw);
> }
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