How to pass size of array in function to function? I don't have “Variable-sized object may not be initialized”

Question

I want to pass the size of array, declared inside a function, to the same function. But then I got the warning "expressiong must a constant value". Are there solutions to this problem?

// Draws a sprite in the console using hex-coded sprite with a specific width
void hex_to_sprite(char* hex_number, int width, int size)
{
    // hex_number = array of hex-coded sprite 
    // width = width of sprite you want to draw
    // size = length of the hex_number multiplied by 4 (0 = 0000, 1 = 0001, etc.)
    char binary_coded_sprite[size] = "";

}

Should I learn dynamic allocation to fight this problem?

Answer 1

You’re declaring binary_coded_sprite as a variable-length array, where the array size isn’t known until runtime. One of the restrictions¹ on VLAs is that they may not be declared with an initializer, so

char binary_coded_sprite[size] = "";

needs to be

char binary_coded_sprite[size];

and you’ll either need to use strcpy:

strcpy( binary_coded_sprite, “” );

or just set the first element to 0

binary_coded_sprite[0] = 0;

to initialize it to an empty string.

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1. The other restrictions are that VLAs may not be declared static or at file scope, nor may they be members of struct or union types.