Opaque C structs: various ways to declare them

by

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 and problematic underscore) is acceptable. But whatever you do, never use typedef to define names for pointer types. It hides the extremely important piece of information that variables of this type reference an object which could be modified whenever you pass them to functions, and it makes dealing with differently-qualified (for instance, const-qualified) versions of the pointer a major pain.

More Related Contents:

  1. Is there a way to use a typedef struct variable in a function…? [closed]
  2. typedef struct vs struct definitions [duplicate]
  3. self referential struct definition?
  4. Why should we typedef a struct so often in C?
  5. How to define a typedef struct containing pointers to itself?
  6. What is ‘forward declaration’ and the difference between ‘typedef struct X’ and ‘struct X’?
  7. C typedef of pointer to structure
  8. C Typedef and Struct Question
  9. C : typedef struct name {…}; VS typedef struct{…} name;
  10. Why does “typdef struct { struct S *s; } S;” containing a pointer to same type compile?
  11. Why declare a struct that only contains an array in C?
  12. C Typedef – Incomplete Type
  13. dereferencing pointer to incomplete type
  14. Usage of uint_8, uint_16 and uint_32
  15. Difference between ‘struct’ and ‘typedef struct’ in C++?
  16. Difference between a Structure and a Union
  17. typedef pointer const weirdness
  18. C – function inside struct
  19. Are “malloc(sizeof(struct a *))” and “malloc(sizeof(struct a))” the same?
  20. How to initialize a structure with flexible array member
  21. what is the difference between struct {0} and memset 0 [duplicate]
  22. How to include a dynamic array INSIDE a struct in C?
  23. Initializing a struct to 0
  24. Do you prefer “if (var)” or “if (var != 0)”? [closed]
  25. How do you use offsetof() on a struct?
  26. How does C return a structure? [duplicate]
  27. C initialize array within structure
  28. offsetof at compile time
  29. Iterating over same type struct members in C
  30. How can I malloc a struct array inside a function? Code works otherwise

Leave a Comment