2018-05-30 03:44:12 +08:00
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README
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======
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This directory holds NuttX libraries. Libraries in NuttX are very special
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creatures. The have these properties:
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1. They can be shared by both application logic and logic within the OS when
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using the FLAT build.
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2. But in PROTECTED and KERNEL modes, they must be built differently: The
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copies used by applications and the OS cannot be the same. Rather,
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separate versions of libraries must be built for the kernel and for
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applications.
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3. When used by the OS, some special care must be taken to assure that the
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OS logic does not disrupt the user's errno value and that the OS does
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not create inappropriate cancellation points.
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2018-08-13 21:39:38 +08:00
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2018-05-30 03:44:12 +08:00
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For example, sem_wait() is both a cancellation point and modifies the
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errno value. So within the FLAT build and without kernel version for
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the PROTECTED and KERNEL builds, the special internal OS interface
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nxsem_wait() must be used. Within libraries, the macro _SEM_WAIT()
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(as defined in include/nuttx/semaphore.h) is used instead. The
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definition of this macro accounts for the different usage environments.
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2018-05-30 08:16:43 +08:00
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NOTE: The libraries under libs/ build differently from other NuttX
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components: There are no build-related files in the libs/ directory; it
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is simply a container for other well-known, individual library directories.
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The upper level Makefile logic is aware of the libraries within the libs/
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container.
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The only real function of the libs/ directory is to prevent the top-level
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directory from becoming cluttered with individual libraries.
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