nuttx/libs
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
======

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.