NuttX libraries

This page discusses the NuttX libraries that can be found in libs/

Libraries in NuttX are very special creatures. They have these properties:

  1. They can be shared by both application logic and logic within the OS when using the FLAT build.

  2. But in PROTECTED and KERNEL modes, they must be built differently: The copies used by applications and the OS cannot be the same. Rather, separate versions of libraries must be built for the kernel and for applications.

  3. When used by the OS, some special care must be taken to assure that the OS logic does not disrupt the user’s errno value and that the OS does not create inappropriate cancellation points.

    For example, sem_wait() is both a cancellation point and modifies the errno value. So within the FLAT build and without kernel version for the PROTECTED and KERNEL builds, the special internal OS interface nxsem_wait() must be used.

NOTE: The libraries under libs/ build differently from other NuttX components: There are no build-related files in the libs/ directory; it is simply a container for other well-known, individual library directories. The upper level Makefile logic is aware of the libraries within the libs/ container.

The only real function of the libs/ directory is to prevent the top-level directory from becoming cluttered with individual libraries.

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