check for OpenBSD 5.9+

Author: kivikakk

src/main.c

@@ -8,7 +8,11 @@
 #include "node.h"
 
 #if defined(__OpenBSD__)
-#include <unistd.h>
+#  include <sys/param.h>
+#  if OpenBSD >= 201605
+#    define USE_PLEDGE
+#    include <unistd.h>
+#  endif
 #endif
 
 #if defined(_WIN32) && !defined(__CYGWIN__)
@@ -81,7 +85,7 @@ int main(int argc, char *argv[]) {
   writer_format writer = FORMAT_HTML;
   int options = CMARK_OPT_DEFAULT;
 
-#if defined(__OpenBSD__)
+#ifdef USE_PLEDGE
   if (pledge("stdio rpath", NULL) != 0) {
     perror("pledge");
     return 1;
@@ -187,7 +191,7 @@ int main(int argc, char *argv[]) {
     }
   }
 
-#if defined(__OpenBSD__)
+#ifdef USE_PLEDGE
   if (pledge("stdio", NULL) != 0) {
     perror("pledge");
     return 1;