Question

I have a large array in C (not C++ if that makes a difference). I want to initialize all members of the same value.

I could swear I once knew a simple way to do this. I could use memset() in my case, but isn’t there a way to do this that is built right into the C syntax?

Answer 1

Unless that value is 0 (in which case you can omit some part of the initializer and the corresponding elements will be initialized to 0), there’s no easy way.

Don’t overlook the obvious solution, though:

int myArray[10] = { 5, 5, 5, 5, 5, 5, 5, 5, 5, 5 }; 

Elements with missing values will be initialized to 0:

int myArray[10] = { 1, 2 }; // initialize to 1,2,0,0,0... 

So this will initialize all elements to 0:

int myArray[10] = { 0 }; // all elements 0 

In C++, an empty initialization list will also initialize every element to 0. This is not allowed with C until C23:

int myArray[10] = {}; // all elements 0 in C++ and C23 

Remember that objects with static storage duration will initialize to 0 if no initializer is specified:

static int myArray[10]; // all elements 0 

And that "0" doesn’t necessarily mean "all-bits-zero", so using the above is better and more portable than memset(). (Floating point values will be initialized to +0, pointers to null value, etc.)