Problem using double quotes as a commandline argument in C++

Question

I'm trying to write a program that detects '-m' as an argument for a message and use double quotes between the message itself. Now I'm just trying to detect if the message starts with double quotes, but I get an unexpected behavior.

The main function:

int main(int argc, char *argv[]){
    if (argc < 3){
        std::cerr << "Error! Bad usage of parameters" << std::endl;
        return 1;
    }

    for (int i = 1; i < argc - 1; i++){
        std::string arg = argv[i];
        std::string nextarg = argv[i+1];
        if(arg == "-m"){
            if(nextarg.empty() || nextarg[0] != '"'){
                std::cout << "nextarg[0]: " << nextarg[0] << std::endl;
                std::cout << "arg: " << arg << std::endl;
                std::cerr << "Error, message must be on double quotes" << std::endl;
                return 1;
            }
            else {
                std::cout << "The code worked" << std::endl;
                std::cout << nextarg << std::endl;
                std::cout << arg << std::endl;
            }
            return 0;
        }
        else{
            std::cerr << "The value is invalid." << std::endl;
            return 1;
        }
    }
}

Now, the input I'm using is ./compiled -m "foo foo", and the expected output is:

The code worked
"foo foo"
-m

But the actual output is:

nextarg[0]: f
arg: -m
Error, message must be on double quotes

So, I see the problem is probably that my program doesn't detect the first double quotes. Also, if I use only one double quotes, the output makes an infinite loop of '>' asking me for an input, I don't want that behavior in my program.

By the way, I don't know why, but my program works if I use this input: ./compiled -m "\"foo foo\"", so I think that must be a problem with the terminal itself, but I still don't know anything about that.