Question

I have written this little weird piece of code. How is this possible that type changes between its 2 printf ??

Thanks in advance

int main()
{
    string label = string("faults_team_A_player_12");

    size_t f = label.find('_');

    const char *type = label.substr(0,f).c_str();
    const char team = label.at(f+sizeof("team_"));

    printf("type = %s\n",type);

    int n;
    size_t l = label.length()-label.find_last_of('_');

    int x = sscanf((char *)label.substr(label.find_last_of('_'),l).c_str(),"_%d",&n);
    printf("type = %s\n",type);
    printf("team = %c\n",team);
    printf("player = %d\n",n);

    return 0;
}

ouptut:

type = faults
type = _12
team = A
player = 12

Answer 1

type is a dangling pointer as it is initialised to the internal member of a temporary std::string instance:

const char *type = label.substr(0,f).c_str();

The std::string instance from which the result of c_str() is obtained is destructed immediately.