This is undefined behaviour except when using msvc. For GCC and clang, you should use [] (empty square brackets) to denote a variable length array at the end of

This is undefined behaviour except when using msvc. For GCC and clang, you should use [] (empty square brackets) to denote a variable length array at the end of a struct. For msvc, [1] is used all over win32 and is explicitly supported for that purpose. Edit: it's UB because you're accessing past the end of an array with size given at compile time.