C – Array Initialization Techniques

arraysc++

I have doubt regarding the following piece of code :

int main()
{
    int array1 = {1,2,3,4,5}; //error in c++ , warning in c
    int array2[] = {1,2,3,4,5};
    int array3[5] = {1,2,3,4,5};
}

This piece of code gives a error on line 3 in c++ but not in c?

I know array1 is actually an int and array2 and array3 are arrays, so why doesn't a c compiler show a error , but just a warning: "excess elements in scalar initialization"

Is there a use of such a definition and why is it valid in c?

Best Answer

It is not valid C. See C11 6.7.9:

No initializer shall attempt to provide a value for an object not contained within the entity being initialized.

I would guess that you are using gcc. Then if you want your program to behave as strict standard C, compile it as such:

gcc -std=c11 -pedantic-errors

gives

error: excess elements in scalar initializer

Related Solutions

C Array Initialization – How to Initialize Arrays in C

From How to initialize all members of an array to the same value?:

Initialize all members to the same value:

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:

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

Objects with static storage duration will initialize to 0 if no initializer is specified:

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

If your compiler is GCC you can use following syntax:

int array[1024] = {[0 ... 1023] = 5};
int A[10] = {[0 ... 4] = 5, [5 ... 9] = 3};

Best Answer

Related Solutions

C Array Initialization – How to Initialize Arrays in C

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