How to initialize a struct in accordance with C programming language standards

Question

I want to initialize a struct element, split in declaration and initialization. This is what I have:

typedef struct MY_TYPE {   bool flag;   short int value;   double stuff; } MY_TYPE;  void function(void) {   MY_TYPE a;   ...   a = { true, 15, 0.123 } } 

Is this the way to declare and initialize a local variable of MY_TYPE in accordance with C programming language standards (C89, C90, C99, C11, etc.)? Or is there anything better or at least working?

Update I ended up having a static initialization element where I set every subelement according to my needs.

Answer 1

In (ANSI) C99, you can use a designated initializer to initialize a structure:

MY_TYPE a = { .flag = true, .value = 123, .stuff = 0.456 }; 

Other members are initialized as zero: "Omitted field members are implicitly initialized the same as objects that have static storage duration." (https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html)

Answer 2

You can do it with a compound literal. According to that page, it works in C99 (which also counts as ANSI C).

MY_TYPE a;  a = (MY_TYPE) { .flag = true, .value = 123, .stuff = 0.456 }; ... a = (MY_TYPE) { .value = 234, .stuff = 1.234, .flag = false }; 

The designations in the initializers are optional; you could also write:

a = (MY_TYPE) { true,  123, 0.456 }; ... a = (MY_TYPE) { false, 234, 1.234 };