How do structs that have been typedef-ed work in C?

December 15, 2022

Structures with tags allow you to make a instances (or whatever an instance is called in c). What about typedef structs though? If the typedef is for the struct keyword to be replaced by a type name, then every time you use the the typename aren’t you just saying that you are replacing the struct keyword with the type name? Example:

typedef struct {
    int x;
    int y;
}TypeName;


int main()
{

    TypeName instance; // isn't this the same as writing struct instance; ?

    return 0;
}

So how does typedef work when you use it on a struct?

>Solution :

It defines a struct with no name and then make TypeName a name for that same struct.

If you like, you can imagine it as if the compiler creates a random name for you (some compilers actually do):

typedef struct __TOTALLY_RANDOM_NAME_wieryweuoi3u4t23423cogh234283 {
    int x;
    int y;
}TypeName;

int main()
{
    struct __TOTALLY_RANDOM_NAME_wieryweuoi3u4t23423cogh234283 instance;

    return 0;
}