Question

I’m getting some very strange behaviour using the following switch statement:

string recognise_mti(int mti_code)
{
switch(mti_code)
    {
    case 1100:
    case 1101:
        return (mti_code + " (Auth. Request/Repeat)"); break;

    default:
        return (mti_code + " (NOT RECOGNISED)"); break;
    }
}

It seems to return all sorts of things depending on the input integer. It’s probably going to turn out to be a silly mistake but as of yet, I’m unable to recognise it. Appreciate any help.

Answer 1

Neither mti_code nor " (Auth. Request/Repeat)" is a std::string. So in fact, all that addition is going to do is pointer addition. So you’ll end up with a somewhat random (and probably invalid) pointer, which is then implicitly converted to a std::string.

Try this:

#include <sstream>

...

std::stringstream ss;
ss << mti_code;
switch(mti_code)
    {
    case 1100:
    case 1101:
        ss << " (Auth. Request/Repeat)"; break;

    default:
        ss << " (NOT RECOGNISED)"; break;
    }
return ss.str();