Use err.h instead of self-implemented error output

main.c

@@ -2,6 +2,7 @@
 #define _GNU_SOURCE
 #include <sched.h>
 #include <errno.h>
+#include <err.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -12,12 +13,6 @@
 
 pid_t pid_child;
 
-void fatal(const char* str, int errcode)
-{
-  printf("%s (%d)\n", str, errcode);
-  exit(errcode);
-}
-
 void drop_root(void)
 {
   /// Drop root privileges
@@ -25,15 +20,15 @@ void drop_root(void)
   // be able to drop group once we dropped user
   gid_t gid = getgid();
   if (setresgid(-1,gid,gid) == -1)
-    fatal("Failed to drop root privileges with setresgid", errno);
+    err(errno, "Failed to drop root privileges with setresgid");
 
   uid_t uid = getuid();
   if (setresuid(-1,uid,uid) == -1)
-    fatal("Failed to drop root privileges with setresuid", errno);
+    err(errno, "Failed to drop root privileges with setresuid");
 
   // sanity check
   if (seteuid(0) != -1)
-    fatal("Sanity check failed. Able to regain root", 42);
+    errx(1, "Sanity check failed. Able to regain root");
 }
 
 struct sigaction forward_signal_descriptor;
@@ -48,8 +43,6 @@ void forward_signal(int sig)
 
 int main(int argc, char* const* argv)
 {
-  int err;
-
   forward_signal_descriptor.sa_flags = SA_RESTART;
   forward_signal_descriptor.sa_handler = &forward_signal;
 
@@ -64,7 +57,7 @@ int main(int argc, char* const* argv)
   // next fork shall be in a new pid namespace
   if (unshare(CLONE_NEWPID) != 0)
     {
-      fatal("Failed to unshare pid namespace", errno);
+      err(errno, "Failed to unshare pid namespace");
     }
 
   // Drop root privileges, we only needed those for the unshare call.
@@ -74,7 +67,7 @@ int main(int argc, char* const* argv)
 
   if (pid == -1)
     {
-      fatal("Failed to fork", errno);
+      err(errno, "Failed to fork");
     }
 
   if (pid != 0)
@@ -94,7 +87,7 @@ int main(int argc, char* const* argv)
       int status;
       if (waitpid(pid, &status, 0) == -1)
         {
-          fatal("Failed to wait for init process", errno);
+          err(errno, "Failed to wait for init process");
         }
 
       return WEXITSTATUS(status);
@@ -109,7 +102,7 @@ int main(int argc, char* const* argv)
       pid = fork();
       if (pid == -1)
         {
-          fatal("Failed to fork in init process", errno);
+          err(errno, "Failed to fork in init process");
         }
 
       if (pid != 0)
@@ -133,18 +126,19 @@ int main(int argc, char* const* argv)
           pid_child = first_child;
           if (sigaction(SIGTERM, &forward_signal_descriptor, NULL) == -1)
             {
-              fatal("Unable to setup signal forward in init", 1);
+              err(1, "Unable to setup signal forward in init");
             }
 
+          int wait_errno;
           // wait could be interrupt due to a signal. In that case just call wait again.
           do {
             exited_child = wait(&child_status);
-            err = errno;
-          } while (!(exited_child == first_child || (exited_child == -1 && err == ECHILD)));
+            wait_errno = errno;
+          } while (!(exited_child == first_child || (exited_child == -1 && wait_errno == ECHILD)));
 
           if (exited_child == -1)
             {
-              return err;
+              err(wait_errno, "Error while waiting for subprocess");
             }
           else
             {
@@ -159,7 +153,7 @@ int main(int argc, char* const* argv)
 
           if (execvp(argv[0], argv) == -1)
             {
-              fatal("Failed to exec", errno);
+              err(errno, "Failed to exec");
             }
         }
     }