dnl These headers are not essential
-AC_CHECK_HEADERS(stdint.h sys/types.h inttypes.h sys/param.h sys/wait.h sys/limits.h netinet/in.h arpa/inet.h machine/limits.h syslog.h sys/time.h sys/resource.h pthread.h)
+AC_CHECK_HEADERS(stdint.h sys/types.h inttypes.h sys/param.h sys/wait.h sys/limits.h netinet/in.h arpa/inet.h machine/limits.h syslog.h sys/time.h sys/resource.h pthread.h stddef.h)
AC_CHECK_FUNCS(gettimeofday ftime socketpair uname inet_aton strptime getrlimit setrlimit strlcat strlcpy strtoull getpwnam ftello pthread_create gethostbyname_r getaddrinfo)
AC_FUNC_FSEEKO
[AC_RUN_IFELSE([AC_LANG_SOURCE(
[[#include <stdlib.h>
#include <string.h>
+#include <stdio.h>
+#ifdef HAVE_STDDEF_H
+#include <stddef.h>
+#endif
int main () { char *p1,*p2; p1=NULL; memset(&p2,0,sizeof(p2));
return memcmp(&p1,&p2,sizeof(char*))?1:0; }]])],
[tor_cv_null_is_zero=yes],