CODEWITHSUNDEEP
cstruct
stanleyli
stanleyli

Reputation: 1477

How to have a const member in all instances of a struct using C (not C++)?

I want to design a struct in C, which is like:

typedef struct {
    const int HEADER;
    int data;
} A_STRUCT;

I hope all the instances of this struct have the same known const HEADER value, e.g. 0x33. Basically, I need a member variable which is initialized automatically in each instance of the struct. What is the correct way to do it in C (not C++)? Esp. how to initialize it?

Upvotes: 1

Views: 2500

Answers (1)

user2371524
user2371524

Reputation:

Note: This answer is invalidated by an edit to the question, removing the objective of a "static member" like in C++. Leaving it here just for reference.

A static member in C++ is essentially a global variable that's scoped in the namespace of the struct/class. So something like this in C++:

foo.h:

struct foo
{
    static int bar;
    int baz;
};

foo.cpp:

int foo::bar = 0x33;

translates roughly to the following in C:

foo.h:

struct foo
{
    int baz;
}
extern int foo_bar;

foo.c:

int foo_bar = 0x33;

Also note the keyword static has an entirely different meaning in C, it declares the variable with static storage; it becomes inaccessible from other translation units.

Upvotes: 1

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