incubator-nuttx

History

Xiang Xiao e160bffe28 Remove all fclose with stdin, stdout and stderr since it is wrong to close the builtin stream and specially note https://pubs.opengroup.org/onlinepubs/9699919799/functions/fclose.html: Since after the call to fclose() any use of stream results in undefined behavior, fclose() should not be used on stdin, stdout, or stderr except immediately before process termination (see XBD Process Termination), so as to avoid triggering undefined behavior in other standard interfaces that rely on these streams. If there are any atexit() handlers registered by the application, such a call to fclose() should not occur until the last handler is finishing. Once fclose() has been used to close stdin, stdout, or stderr, there is no standard way to reopen any of these streams. and it is also unnecessary because the stream always get flushed. Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>		2020-10-29 20:43:50 +09:00
..
libc	Remove all fclose with stdin, stdout and stderr	2020-10-29 20:43:50 +09:00
libdsp	Fix nxstyle warnings	2020-10-10 12:24:28 -06:00
libnx	use "export" to expose TOPDIR to all child make instead of passing it around every time	2020-09-15 21:11:33 -07:00
libxx	libxx: Use Kconfig "choice" to specify an implemenetation	2020-10-28 14:10:30 -03:00
README.txt	libs/README.txt: Fix a typo	2020-01-27 08:46:46 +01:00

README.txt

README
======

This directory holds NuttX libraries.  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.  Within libraries, the macro _SEM_WAIT()
   (as defined in include/nuttx/semaphore.h) is used instead.  The
   definition of this macro accounts for the different usage environments.

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.