"no matching function for call" in initialiser list for char [] [duplicate]

Question

I have the below code. The first push_back fails, the second, with a constant string, works.

#include <vector>
#define MAX_LENGTH 10
    
struct bar
{
    int  barInt;
    char barChar [MAX_LENGTH];
};
    
int main()
{
    char fooString [MAX_LENGTH] = "Hello";
    std::vector<bar> foo {};
        
    foo.push_back( { 1 , fooString } );  // error: no matching function for call to ‘std::vector::push_back()’
    foo.push_back( { 1 , "Hello" } );    // Works
}

Live demo - OnlineGDB

Sorry guys, but I don't get it really. What is the problem? A copy issue?

PS: std::string is in the whole context not an option.

Answer 1

In order to work, this line:

foo.push_back( { 1 , fooString } );

has to copy fooString into the barChar member of the new bar element.

But C strings which are actually [zero terminated] char arrays are non-copyable (see e.g. here), hence the error.

The other case (foo.push_back( { 1 , "Hello" } );) is OK because you can initialize a C string with a string literal.

One solution is to create a temporary bar object to push_back into the std::vector.
Alternatively as @user7860670 commented, you can avoid the temporary by pushing a zero initialized bar and setting the fields afterwards in the element inside the vector.

Note:
Unlike C arrays, std::array is copyable.
If you can use it instead of the C array it might be the simplest solution.
However - in order to initialize an std::array with a string you need to use uniform initialization syntax: std::array<char, MAX_LENGTH> fooString{"Hello"};.

A side note:
Instead of using a #define for your constant (MAX_LENGTH) you can consider to use a compile time constant (constexpr) which is considered more idiomatic.
See: Defining global constant in C++.