Apache NuttX is a mature, real-time embedded operating system (RTOS) https://nuttx.apache.org/
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Marco Casaroli ca8287e690 Documentation: describe the fork()/vfork()/task_fork() split
Documentation/guides/fork_vfork_migration.rst is new.  It says what changed
and why, gives the three primitives as a table, states plainly what breaks,
and answers "which replacement do I want?" from the reader's own reason for
having called fork() -- posix_spawn() or vfork() to run a program,
pthread_create() or task_fork() for a second flow of control that shares
memory, fork() itself for an independent copy, FORK_IS_TASK_FORK for code
that cannot be changed today.  It also documents the seven configuration
symbols, what an architecture has to implement to gain real fork(), and the
one visible consequence of moving the vfork() suspension into the kernel:
a waitpid() after a child that _exit()s can only report status where
CONFIG_SCHED_CHILD_STATUS is enabled.

reference/user/01_task_control.rst gains entries for fork() and task_fork()
and rewrites the one for vfork(), which described NuttX's limitations rather
than the interface's contract.  standards/posix.rst moves fork() from "No" to
"Cond." and vfork() from "Yes" to "Cond.", both being conditional on the
configuration now.  implementation/memory_configurations.rst no longer lists
fork() as unimplementable in the presence of address environments, which was
the whole point of that section's wish list.  Three long-standing typos in
that file are corrected while touching it, since codespell checks the whole
of any file a patch modifies.

Signed-off-by: Marco Casaroli <marco.casaroli@gmail.com>

Assisted-by: Claude Opus 5 (1M context) <noreply@anthropic.com>
2026-07-30 11:45:24 +02:00
.github build(deps): bump actions/setup-python from 6 to 7 2026-07-27 13:34:36 -04:00
arch sched/arch/libc: give fork(), vfork() and task_fork() separate semantics 2026-07-29 16:39:07 +02:00
audio tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
binfmt tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
boards boards/risc-v/esp32c6: Add SW LP Mailbox board support 2026-07-29 09:53:59 +08:00
cmake cmake: Omit default priority ELF symbol. 2026-07-27 14:30:42 +08:00
crypto tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
Documentation Documentation: describe the fork()/vfork()/task_fork() split 2026-07-30 11:45:24 +02:00
drivers drivers/syslog: fix syslog_write() returning -EIO on every write 2026-07-29 07:57:29 +02:00
dummy
fs tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
graphics tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
include sched/arch/libc: give fork(), vfork() and task_fork() separate semantics 2026-07-29 16:39:07 +02:00
libs sched/arch/libc: give fork(), vfork() and task_fork() separate semantics 2026-07-29 16:39:07 +02:00
mm tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
net tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
openamp tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
pass1 tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
sched sched/arch/libc: give fork(), vfork() and task_fork() separate semantics 2026-07-29 16:39:07 +02:00
syscall sched/arch/libc: give fork(), vfork() and task_fork() separate semantics 2026-07-29 16:39:07 +02:00
tools tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
video tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
wireless tools: fix stale archive members surviving a Kconfig-driven CSRCS change 2026-07-28 21:26:03 -03:00
.asf.yaml github: master branch protection tune. 2025-05-07 18:37:13 -05:00
.codespell-ignore-lines arch/arm: Reserve r10 via ARCHCFLAGS and hoist the PIC module flags. 2026-07-24 23:09:08 +08:00
.codespellrc arch/arm/rp23xx: Add hardware TRNG driver for /dev/random. 2026-07-25 15:06:56 +08:00
.editorconfig .editorconfig: fix character encoding property specification 2025-11-28 19:12:13 +08:00
.gitignore git: Specify multiple build directories in .gitignore. 2026-05-20 03:06:58 +08:00
.gitmessage docs/contributing: Add a commit message template 2025-06-03 17:33:24 +08:00
.pre-commit-config.yaml
.yamllint
AUTHORS AUTHORS: add Eren Terzioglu 2026-05-20 15:17:00 +08:00
CMakeLists.txt cmake: Do not link an executable to detect the compiler. 2026-07-25 22:52:39 +08:00
CONTRIBUTING.md contributing: Add requirement for 'Assisted-by' commit field 2026-07-12 09:42:28 +08:00
INVIOLABLES.md
Kconfig sched/misc/assert: Add CONFIG_SCHED_DUMP_TASKS and CONFIG_SCHED_DUMP_STACK 2026-06-09 08:04:54 -04:00
LICENSE libs/libdsp: Add Matrix operations 2026-07-11 14:55:59 -03:00
Makefile !boards: enforce secure ROMFS passwd and TEA key setup 2026-07-09 22:41:11 +08:00
NOTICE
README.md ci/testing: Add MemBrowse Integration 2026-06-18 12:07:41 -03:00
ReleaseNotes

POSIX Badge License Issues Tracking Badge Contributors GitHub Build Badge Documentation Badge MemBrowse

Apache NuttX is a real-time operating system (RTOS) with an emphasis on standards compliance and small footprint. Scalable from 8-bit to 64-bit microcontroller environments, the primary governing standards in NuttX are POSIX and ANSI standards. Additional standard APIs from Unix and other common RTOSs (such as VxWorks) are adopted for functionality not available under these standards, or for functionality that is not appropriate for deeply-embedded environments (such as fork()).

For brevity, many parts of the documentation will refer to Apache NuttX as simply NuttX.

Getting Started

First time on NuttX? Read the Getting Started guide! If you don't have a board available, NuttX has its own simulator that you can run on terminal.

Documentation

You can find the current NuttX documentation on the Documentation Page.

Alternatively, you can build the documentation yourself by following the Documentation Build Instructions.

The old NuttX documentation is still available in the Apache wiki.

Supported Boards

NuttX supports a wide variety of platforms. See the full list on the Supported Platforms page.

Contributing

If you wish to contribute to the NuttX project, read the Contributing guidelines for information on Git usage, coding standard, workflow and the NuttX principles.

License

The code in this repository is under either the Apache 2 license, or a license compatible with the Apache 2 license. See the License Page for more information.