C++ Segmentation Fault: 11 while scanning arguments

Question

I am sure this question should be an easy answer, but I have been stumped for a while now. In my code, I have the main function: auto-generated, with the arguments as parameters. Then, I process the arguments and check if flags should be enabled or not. However, when I send a flag file -d or file -s, it throws a Segmentation fault: 11 (note that the text in cout gets printed). The code seems simple, thanks for any advice.

int main(int argc, const char * argv[]) {
    srand(time(0));
    bool d_on = false;
    bool s_on = false;
    
    if (argc > 1) {
        for (int i = 1; i <= argc; i++) {
            string arg = argv[i];
            
            if ((arg == "-h") || (arg == "--help")) {
                printHelpExit();
            } else if ((arg == "-d") || (arg == "--debug")) {
                cout << "DEBUG ON" << endl;
                d_on = true;
            } else if ((arg == "-s") || (arg == "-solver")) {
                cout << "SOLVER ON" << endl;
                s_on = true;
            } else {
                cout << "Invalid argument: " << arg << endl;
                printHelpExit();
            }
        }
    }

    return 0;

`i <= argc` ==> `i < argc`, `argc` is already an invalid index for `argv`. — mch, Oct 06 '22 at 15:17
@NathanOliver `arg` seems to be a `string`, the C++ `std::string`, not the CS50 `string`. — mch, Oct 06 '22 at 15:18
`argv[argc]` isn't an invalid index; it is guaranteed to be `nullptr`, and generally there is not any need to access that index. — Eljay, Oct 06 '22 at 15:18
@Eljay Then how would you suggest I check command-line arguments? — cold10, Oct 06 '22 at 15:24
First line of main's body: `vector args(argv+1, argv+argc);` Now `args` is nicely C++ object-ified of the executable's command line parameters. — Eljay, Oct 06 '22 at 15:25
Change this `i <= argc` to this `i < argc` in the for-loop. While `argv[argc]` is guaranteed to be valid, it's equal to nullptr and trying to initialize `std::string` from nullptr is what's causing the segfault. — Super-intelligent Shade, Oct 06 '22 at 15:36

C++ Segmentation Fault: 11 while scanning arguments

0 Answers0