Here's an example struct declaration Qt Creator has problems with:

struct MyStruct
{
char a;
char b;
} _attribute_((packed));

Qt Creator fails to parse that struct. It won't autocomplete its fields, it won't go to its declaration, and so on. It just doesn't exist for it.

The _attribute_ mechanism is a standard gcc feature which quite widely used. It's the only way to declare structure packing, for example. It would be nice if Qt Creator would parse such declarations correctly.