19-02-2009, 11:11 PM
Please help me understand the reason for rule 18.1. In the context of an "opaque pointer", one can properly make and use such a pointer to an incompletely typed structure. Having the full structure declaration is not needed. The committee has endorsed this in a previous post.
What coding practice is left that might cause a problem? If the type is incomplete, a compile error will result from any attempt to create an object of that type or refer to its members.
OK, but even so, why not require it? In header files, I like to code:
struct something; /* with a forward declaration, I can create pointers. */
void foo (struct something *pointerToSomething);
The prototype is valid even though "something" is of incomplete type. If the #including .c file does not need anything other than the pointer, why require #including yet another header merely to get the (unused) full declaration and satisfy the rule?
What coding practice is left that might cause a problem? If the type is incomplete, a compile error will result from any attempt to create an object of that type or refer to its members.
OK, but even so, why not require it? In header files, I like to code:
struct something; /* with a forward declaration, I can create pointers. */
void foo (struct something *pointerToSomething);
The prototype is valid even though "something" is of incomplete type. If the #including .c file does not need anything other than the pointer, why require #including yet another header merely to get the (unused) full declaration and satisfy the rule?