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author | Sebastian Huber <sebastian.huber@embedded-brains.de> | 2020-09-01 07:03:49 +0200 |
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committer | Sebastian Huber <sebastian.huber@embedded-brains.de> | 2020-09-02 07:18:22 +0200 |
commit | 491567efffa970e6151ca8fb27afa1a2798fbb6c (patch) | |
tree | a0c3dc96056fa922608ebb6b0557c416e93d9651 | |
parent | user: Fix format (diff) | |
download | rtems-docs-491567efffa970e6151ca8fb27afa1a2798fbb6c.tar.bz2 |
user: Mention file descriptor changes
-rw-r--r-- | user/migration/v4_11-to-v5.rst | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/user/migration/v4_11-to-v5.rst b/user/migration/v4_11-to-v5.rst index d42744d..bde84c2 100644 --- a/user/migration/v4_11-to-v5.rst +++ b/user/migration/v4_11-to-v5.rst @@ -69,6 +69,25 @@ The directive :c:func:`rtems_clock_get` was removed. See section `Transition Advice for the Removed rtems_clock_get()` in the `RTEMS Classic API Guide` for alternatives. +File Descriptors +---------------- + +In RTEMS 5.1, the list of free file descriptors has a LIFO ordering in contrast +to previous versions where it was a FIFO. This means if an application +regularly opens and closes files (or sockets) it sees the whole range of file +descriptors. The reason for this change was to increase the time before file +descriptors are reused to more likely catch a file descriptor use after close. + +This change may surface application issues. If the configured file descriptor +maximum (``CONFIGURE_MAXIMUM_FILE_DESCRIPTORS``) is greater than the +``FD_SETSIZE`` defined by Newlib to 64, then calls to ``select()`` are undefined +behaviour and may corrupt the thread stack. In particular, ``FD_SET()`` may +result in an out of bounds access. It is possible to define a custom +``FD_SETSIZE``. The application must ensure that the custom ``FD_SETSIZE`` is +defined before ``<sys/select.h>`` is included in all modules used by the +application, for example via a global compiler command line define. This +applies also to all third-party libraries used by the application. + Networking ---------- |