How to recover from segmentation fault on C++?

Question

I have some production-critical code that has to keep running.

think of the code as

while (true){
   init();
   do_important_things();  //segfault here
   clean();
}

I can't trust the code to be bug-free, and I need to be able to log problems to investigate later.

This time, I know for a fact somewhere in the code there is a segmentation fault getting thrown, and I need to be able to at least log that, and then start everything over.

Reading here there are a few solutions, but following each one is a flame-war claiming the solution will actually do more harm than good, with no real explanation. I also found this answer which I consider using, but I'm not sure it is good for my use case.

So, what is the best way to recover from segmentation fault on C++?

Answer 1

I suggest that you create a very small program that you make really safe that monitors the buggy program. If the buggy program exits in a way you don't like, restart the program.

Posix example:

#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

#include <cstdio>
#include <iostream>

int main(int argc, char* argv[]) {
    if(argc < 2) {
        std::cerr << "USAGE: " << argv[0] << " program_to_monitor <arguments...>\n";
        return 1;
    }

    while(true) {
        pid_t child = fork();          // create a child process

        if(child == -1) {
            std::perror("fork");
            return 1;
        }

        if(child == 0) {
            execvp(argv[1], argv + 1); // start the buggy program
            perror(argv[1]);           // starting failed
            std::exit(0);              // exit with 0 to not trigger a retry
        }

        // Wait for the buggy program to terminate and check the status
        // to see if it should be restarted.

        if(int wstatus; waitpid(child, &wstatus, 0) != -1) {
            if(WIFEXITED(wstatus)) {
                if(WEXITSTATUS(wstatus) == 0) return 0; // normal exit, terminate

                std::cerr << argv[0] << ": " << argv[1] << " exited with "
                          << WEXITSTATUS(wstatus) << '\n';
            }
            if(WIFSIGNALED(wstatus)) {
                std::cerr << argv[0] << ": " << argv[1]
                          << " terminated by signal " << WTERMSIG(wstatus);
                if(WCOREDUMP(wstatus)) std::cout << " (core dumped)";
                std::cout << '\n';
            }
            std::cout << argv[0] << ": Restarting " << argv[1] << '\n';
        } else {
            std::perror("wait");
            break;
        }
    }
}