An “opaque type” is a type where you don’t have a full definition for the struct or class. In C, C++ and Objective-C, you can tell the compiler that a type will be defined later by using a forward declaration: // forward declaration of struct in C, C++ and Objective-C struct Foo; // forward declaration … Read more
You can use the _alloca function. I believe that it’s not exactly Standard, but as far as I know, nearly all common compilers implement it. When you use it as a default argument, it allocates off the caller’s stack. // Header typedef struct {} something; size_t get_size(); something* create_something(void* mem); // Usage something* ptr = … Read more
My vote is for the third option that mouviciel posted then deleted: I have seen a third way: // foo.h struct foo; void doStuff(struct foo *f); // foo.c struct foo { int x; int y; }; If you really can’t stand typing the struct keyword, typedef struct foo foo; (note: get rid of the useless … Read more
An opaque pointer is one in which no details are revealed of the underlying data (from a dictionary definition: opaque: adjective; not able to be seen through; not transparent). For example, you may declare in a header file (this is from some of my actual code): typedef struct pmpi_s *pmpi; which declares a type pmpi … Read more