Porting code

The Interix subsystem is, at its base, a POSIX.1-conformant subsystem. It also supports a variety of features, including sockets, Berkeley Software Distribution (BSD) 4.4 interfaces, System V interprocess communication (IPC) mechanisms, pseudo terminals, and memory mapped files.

Applications are often written for one operating system and ported to another by using some combination of conditional compilation (#ifdef preprocessor commands) or wrapper functions. Porting software to the Interix subsystem involves:

• Making the source portable. That is, choosing the features supported by the Interix subsystem. These features include the POSIX.1 interface, as well as extensions taken from other standards, such as the Single UNIX Specification, and extensions taken from traditional systems, such as BSD or System V derivatives.
• Addressing issues specific to Interix subsystem.

Programs are usually ported by typing make(1) in the source directory. After you have done this, you can fix problems reported by the compiler. The following changes are some of the most common you might need to make:

• Select the appropriate compile flags for a POSIX.1 system.
• Replace the VARARGS macros with STDARG macros. Although both macro sets are provided, the STDARG macros are standard.

This section covers:

• Writing standard POSIX code
• Extensions to POSIX.1
• Issues specific to the Interix subsystem
• Debugging ported code
• Resources