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<pre> #include <netdb.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <errno.h> #define CANARY "in_the_coal_mine" struct {   char buffer[1024];   char canary[sizeof(CANARY)]; } temp = { "buffer", CANARY }; int main(void) {   struct hostent resbuf;   struct hostent *result;   int herrno;   int retval;   /*** strlen (name) = size_needed – sizeof (*host_addr) – sizeof (*h_addr_ptrs) – 1; ***/   size_t len = sizeof(temp.buffer) – 16*sizeof(unsigned char) – 2*sizeof(char *) – 1;   char name[sizeof(temp.buffer)];   memset(name, ‘0’, len);   name[len] = ‘\0’;   retval = gethostbyname_r(name, &resbuf, temp.buffer, sizeof(temp.buffer), &result, &herrno);   if (strcmp(temp.canary, CANARY) != 0) {     puts("vulnerable");     exit(EXIT_SUCCESS);   }   if (retval == ERANGE) {     puts("not vulnerable");     exit(EXIT_SUCCESS);   }   puts("should not happen");   exit(EXIT_FAILURE); } </pre>