nitpicking and better c standard compliant code

challenge/challenge.c

 #include <string.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <errno.h>
 
-int main() {
-    int ret;
-    size_t nbytes = 0;
-    char *input_str = NULL;
-    char *password = "23door42\n";
+const char *password = "23door42\n";
+
+int main(void) {
+    size_t input_size = 0;
+    char *input_line = NULL;
 
     printf("Please enter Password: ");
-    ret = getline(&input_str, &nbytes, stdin);
 
-    if (ret == -1) {
-        puts("Error");
-    } else if (strcmp(input_str, password) == 0) {
-        puts("Success");
-        ret = 0;
+    // read in password from standard input, exit on error.
+    if (getline(&input_line, &input_size, stdin) == -1) {
+        perror("Error");
+        exit(EXIT_FAILURE);
+    }
+
+    // compare password, print info, exit appropriately
+    if (strcmp(input_line, password) == 0) {
+        puts("Success!");
+        exit(EXIT_SUCCESS);
     } else {
         puts("How about no?!");
-        ret = -1;
+        exit(EXIT_FAILURE);
     }
-
-    free(input_str);
-    return ret;
 }