On Tue, 18 May 2010 22:01:57 +0200
Andreas Volz <[email protected]> wrote:
> Hello,
>
> I noticed a problem in the Elementary GenList example code:
>
> static Elm_Genlist_Item_Class itc1;
> char *gl_label_get(const void *data, Evas_Object *obj, const char
> *part) {
> char buf[256];
> snprintf(buf, sizeof(buf), "Item # %i", (int)data);
> return strdup(buf);
> }
>
> static void
> gl_sel(void *data, Evas_Object *obj, void *event_info)
> {
> printf("sel item data [%p] on genlist obj [%p], item pointer
> [%p]\n", data, obj, event_info);
> printf ("data val: %i\n", (int) data);
> }
>
> void
> test_genlist(void *data, Evas_Object *obj, void *event_info
> {
> int i;
> ...
>
> for (i = 0; i < 2000; i++)
> {
> gli = elm_genlist_item_append(gl, &itc1,
> (void *)i/* item data */,
> NULL/* parent */,
> ELM_GENLIST_ITEM_NONE,
> gl_sel/* func */,
> (void *)(i * 10)/* func data
> */); ...
> }
>
> While wrapping GenList to C++ I noticed that something really bad
> happens here. The value of 'i' and 'i*10' is casted into a pointer
> type and later casted back to int. I'm really sure this code isn't
> covered by the C standard and not portable in any way. This code
> needs the int type to have the same size as a pointer type. But there
> may be architectures/compilers where this isn't the case. And even if
> this works here it may bring someone to the idea to do the same with
> other integral types where this won't work for sure. Not a smart idea
> in a public example...
>
> If you think this is correct code and I'm wrong please enlighten
> me. :-)
It's technically not correct. Yes it hits something undefined in there.
Practically however it's only a problem if sizeof(int) > sizeof(ptr) or
some weird platform which doesn't support odd pointers or something
(cray I's?). Don't think efl runs on any of those platforms ;-)
Pratically it's fine. A slight improvement may be to cast it to an
intptr_t which will protect it against different size void/int's (And
will reduce warnings too).
> If not I'll change the example to hold two int arrays in the correct
> scope and work with pointer type data.
Or do that ;-)
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