### Porting Hints

NOTE: The following procedures have been replaced by GNU automake and autoconfigure. This page is to be updated in the next release.

Porting to a new machine or operating system ordinarily requires updating the `./machines` directory and the `./compilers` directories in order to define the build environment and autoconfigure means. You will probably have to modify the `ntp_machines.h` file and `"l_stdlib.h"` files as well. The two most famous trouble spots are the I/O code in `./ntpd/ntp_io.c` and the clock adjustment code in `./ntpd/ntp_unixclock.c`.

These are the rules so that older bsd systems and the POSIX standard system can coexist together.

1. If you use `select` then include `"ntp_select.h"`. `select` is not standard, since it is very system dependent as to where it is defined. The logic to include the right system dependent include file is in `"ntp_select.h"`.

2. Always use POSIX definition of strings. Include `"ntp_string.h"` instead of `<string.h>`.

3. Always include `"ntp_malloc.h"` if you use `malloc`.

4. Always include `"ntp_io.h"` instead of `<sys/file.h>` or `<fnctl.h>` to get `O_*` flags.

5. Always include `"ntp_if.h"` instead of `<net/if.h>`.

6. Always include `"ntp_stdlib.h"` instead of `<stdlib.h>`.

7. Define any special defines needed for a system in `./include/ntp_machine.h` based on system identifier. This file is included by the `"ntp_types.h"` file and should always be placed first after the `<>` defines.

8. Define any special library prototypes left over from the system library and include files in the `"l_stdlib.h"` file. This file is included by the `"ntp_stdlib.h"` file and should ordinarily be placed last in the includes list.

9. Don't define a include file by the same name as a system include file.

`"l_stdlib.h"` can contain any extra definitions that are needed so that `gcc` will shut up. They should be controlled by a system identifier and there should be a separate section for each system. Really this will make it easier to maintain.

See `include/ntp_machines.h` for the various compile time options.

When you are satisfied the port works and that other ports are not adversely affected, please send patches for the system files you have changed, as well as any documentation that should be updated, including the advice herein.

Good luck.