Initialize char arrays from string literal

Question

I have a struct with char array inside it, however I can't find a decent way to initialize it if string becomes longer.

struct T
{
    char id[4];
};

T t{ 'a','b', 'c','d'}; // case 1: OK

T t{"abcd"};   // case 2: ERROR, "abcd" size is 5, too long for id

I get below error:

   error: initializer-string for array of chars is too long [-fpermissive]
     T t{"abcd"};

The reason is that string literal "abcd" contains null terminator, so the size is 5.

This syntax is allowed C99 string literals , how can I work around in C++11?

Answer 1

You're out of luck. If you can't change T then there is no workaround unless you give up on direct initialization. You'll have to use T t{'a', 'b', 'c'}; etc. This is because T is an aggregate, so the only form of initialization is to pass actual initializers for each element.

Of course you can write a function, eg:

T t = T_from_literal("abcdefgh...");

where that function uses std::copy or similar to copy the characters into a T t; and returns by value, taking advantage of copy elision.

Answer 2

You may mind the '\\0' char in the end of the string when initializing, so you always have to take one more char to make it work:

struct T
{
    char id[5];
};

See this example