C++ array initialization

Question

is this form of intializing an array to all 0s

char myarray[ARRAY_SIZE] = {0} supported by all compilers? ,

if so, is there similar syntax to other types? for example

bool myBoolArray[ARRAY_SIZE] = {false}

Answer 1

yes

i think it should work, i did not try but i believe it works

Answer 2

Yes, I believe it should work and it can also be applied to other data types.

For class arrays though, if there are fewer items in the initializer list than elements in the array, the default constructor is used for the remaining elements. If no default constructor is defined for the class, the initializer list must be complete — that is, there must be one initializer for each element in the array.

Answer 3

Yes, this form of initialization is supported by all C++ compilers. It is a part of C++ language. In fact, it is an idiom that came to C++ from C language. In C language = { 0 } is an idiomatic universal zero-initializer. This is also almost the case in C++.

Since this initalizer is universal, for bool array you don't really need a different "syntax". 0 works as an initializer for bool type as well, so

bool myBoolArray[ARRAY_SIZE] = { 0 };

is guaranteed to initialize the entire array with false. As well as

char* myPtrArray[ARRAY_SIZE] = { 0 };

in guaranteed to initialize the whole array with null-pointers of type char *.

If you believe it improves readability, you can certainly use

bool myBoolArray[ARRAY_SIZE] = { false };
char* myPtrArray[ARRAY_SIZE] = { NULL };

but the point is that = { 0 } variant gives you exactly the same result.

However, in C++ = { 0 } might not work for all types, like enum types, for example, which cannot be initialized with integral 0. Specifically for this reason, C++ supports the shorter form

T myArray[ARRAY_SIZE] = {};

i.e. just an empty pair of {}. This will default-initialize an array of any type (assuming the elements allow default initialization), which means that for basic (scalar) types the entire array will be properly zero-initialized.