return strerror as second value, just like pledge

Author: n0la

example/openbsd-example.lua

@@ -1,17 +1,16 @@
 o = require("openbsd")
 
 -- Test out unveil
-ret = o.unveil(".", "rwx")
-print("unveil: " .. ret)
+ret, errstr = o.unveil(".", "rwx")
+print("unveil:", ret, errstr)
 
 -- Same as pledge("rpath", NULL)
 ret, s = o.pledge("rpath stdio")
-print(ret, s)
+print("pledge:", ret, s)
 
 -- Same as pledge("rpath stdio wpath", "rpath stdio")
 ret, s = o.pledge("rpath stdio wpath", "rpath stdio")
-
-print(ret, s)
+print("pledge:", ret, s)
 
 print(o.arc4random())
 

src/lua-openbsd.c

@@ -98,6 +98,11 @@ int lua_unveil(lua_State *L)
     ret = unveil(path, mode);
     lua_pushnumber(L, ret);
 
+    if (ret == -1) {
+        lua_pushstring(L, strerror(errno));
+        return 2;
+    }
+
     return 1;
 }