Apache NuttX is a mature, real-time embedded operating system (RTOS) https://nuttx.apache.org/
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Xiang Xiao c47b1e2c5b !sys/types.h: change time_t and clock_t to int64_t to align with other OSes
POSIX leaves the signedness of time_t and clock_t unspecified, but
mainstream implementations (Linux glibc/musl, the BSDs, macOS, RTEMS,
Zephyr's POSIX layer, Windows _time64) expose time_t as signed 64-bit.
NuttX has historically used uint64_t only because it was tied to the
CONFIG_SYSTEM_TIME64 knob; with that gone, switch:

  time_t   : uint64_t  -> int64_t
  clock_t  : uint64_t  -> int64_t
  CLOCK_MAX: UINT64_MAX -> INT64_MAX

This lets (time_t)-1 sentinels, negative tick deltas, and host-side
headers behave as on every other POSIX system without source churn.

Headers updated:
  - include/sys/types.h, include/limits.h, include/nuttx/clock.h
  - include/nuttx/fs/hostfs.h (nuttx_time_t alias)
  - include/nuttx/{mqueue.h,wdog.h,wqueue.h,timers/clkcnt.h}

Because clock_t is now signed 64-bit, the NuttX-internal sclock_t
alias becomes redundant: every sclock_t/SCLOCK_MAX use is folded
back to clock_t/CLOCK_MAX (notably in sched/wdog, sched/mqueue,
sched/sched, sched/clock, sched/timer, libs/libc/time, fs/vfs and
the drivers/arch consumers below).

Tick/period constants (NSEC_PER_SEC, USEC_PER_SEC, MSEC_PER_SEC,
SEC_PER_MIN, ...) in include/nuttx/clock.h are retyped from "long"
literals to INT64_C(...) so that 64-bit arithmetic no longer
depends on the host's long width.

Strip now-redundant (time_t)/(clock_t)/(unsigned long) casts and
unsigned-only branches across the tree:
  - arch RTC / oneshot / tickless lowerhalfs:
      arm: cxd56xx, efm32, imxrt, lc823450, max326xx, sam34, sama5,
           samd5e5, samv7, stm32, stm32f7, stm32h7, stm32l4, stm32wb,
           xmc4
      mips: pic32mz       sparc: bm3803       x86_64: intel64
      risc-v/xtensa: espressif (esp_i2c[_slave], esp_rtc,
           esp32c3{_i2c,_rtc,_wifi_adapter}, esp32{,s2,s3}_*),
           mpfs_perf
  - drivers: audio/tone, input/aw86225, power/pm/{activity,
           stability}_governor, rpmsg/rpmsg_ping,
           timers/{ds3231,mcp794xx,pcf85263,rx8010},
           wireless/ieee80211/bcm43xxx, wireless/spirit/spirit_spi
  - core: fs/vfs/{fs_poll,fs_timerfd}, mm/iob/iob_alloc,
          libs/libc/{netdb/lib_dnscache,time/{lib_calendar2utc,
          lib_time}}, net/icmp/icmp_pmtu, net/icmpv6/icmpv6_pmtu,
          net/ipfrag, net/tcp/{tcp.h,tcp_timer},
          net/utils/net_snoop, net/mld/mld_query (drop the now-dead
          mld_mrc2mrd helper since signed math handles it directly),
          sched/clock/{clock,clock_initialize},
          sched/sched/{sched_profil,sched_setparam,sched_setscheduler},
          sched/pthread/pthread_create,
          sched/wdog/{wd_gettime,wd_start,wdog.h},
          sched/timer/timer_gettime, sched/mqueue/*

Flip the few in-tree printf format strings that assumed an
unsigned 64-bit tv_sec:
  * drivers/rpmsg/rpmsg_ping.c                       PRIu64 -> PRId64
  * arch/xtensa/src/esp32{,s2,s3}/esp32*_oneshot_lowerhalf.c
                                          PRIu32 (already wrong) -> PRId64

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
2026-05-19 16:21:28 +08:00
.github ci: retry git clone for nuttx-ntfc-testing 2026-05-12 08:45:30 -03:00
arch !sys/types.h: change time_t and clock_t to int64_t to align with other OSes 2026-05-19 16:21:28 +08:00
audio include/debug.h: Move to include/nuttx/debug.h 2026-04-07 07:50:06 -03:00
binfmt include/debug.h: Move to include/nuttx/debug.h 2026-04-07 07:50:06 -03:00
boards !sched/clock: remove CONFIG_SYSTEM_TIME64 and always use 64-bit time 2026-05-19 16:21:28 +08:00
cmake cmake: Moved the creation of the nxtmpdir folder to the root CMake file 2026-04-22 06:22:36 +08:00
crypto include/debug.h: Move to include/nuttx/debug.h 2026-04-07 07:50:06 -03:00
Documentation !sched/clock: remove CONFIG_SYSTEM_TIME64 and always use 64-bit time 2026-05-19 16:21:28 +08:00
drivers !sys/types.h: change time_t and clock_t to int64_t to align with other OSes 2026-05-19 16:21:28 +08:00
dummy build: add initial cmake build system 2023-07-08 13:50:48 +08:00
fs !sys/types.h: change time_t and clock_t to int64_t to align with other OSes 2026-05-19 16:21:28 +08:00
graphics include/debug.h: Move to include/nuttx/debug.h 2026-04-07 07:50:06 -03:00
include !sys/types.h: change time_t and clock_t to int64_t to align with other OSes 2026-05-19 16:21:28 +08:00
libs !sys/types.h: change time_t and clock_t to int64_t to align with other OSes 2026-05-19 16:21:28 +08:00
mm !sys/types.h: change time_t and clock_t to int64_t to align with other OSes 2026-05-19 16:21:28 +08:00
net !sys/types.h: change time_t and clock_t to int64_t to align with other OSes 2026-05-19 16:21:28 +08:00
openamp openamp: fix CMake dcache option 2026-05-10 15:03:24 +02:00
pass1 Makefile: Remove make depend files by make distclean 2026-02-16 16:27:57 +01:00
sched !sys/types.h: change time_t and clock_t to int64_t to align with other OSes 2026-05-19 16:21:28 +08:00
syscall syscall: fcntl param3 type to uintptr_t 2026-04-27 12:01:55 -03:00
tools arch/arm/stm32n6: Add STM32N6 chip support. 2026-05-18 14:50:29 -03:00
video video: ensure video library is non-empty 2026-05-08 19:51:39 +08:00
wireless include/debug.h: Move to include/nuttx/debug.h 2026-04-07 07:50:06 -03:00
.asf.yaml github: master branch protection tune. 2025-05-07 18:37:13 -05:00
.codespell-ignore-lines !boards: Remove NSH_ARCHINIT and board_app_initialize 2026-05-02 18:36:46 +08:00
.codespellrc codespellrc: add ist to ignorelist 2025-10-14 17:42:01 +08:00
.editorconfig .editorconfig: fix character encoding property specification 2025-11-28 19:12:13 +08:00
.gitignore arch/*/src/Makefile: Avoid uncessary relinking of the nuttx binary. 2026-05-18 09:33:58 +02:00
.gitmessage docs/contributing: Add a commit message template 2025-06-03 17:33:24 +08:00
.pre-commit-config.yaml pre-commit: enable codespell checks 2025-05-05 12:34:39 +08:00
.yamllint feat: add a GitHub action to lint the YAML files 2020-12-15 09:52:04 -06:00
AUTHORS AUTHORS: add Donny Jiuzhu 2026-02-25 10:17:40 +01:00
CMakeLists.txt cmake: Moved the creation of the nxtmpdir folder to the root CMake file 2026-04-22 06:22:36 +08:00
CONTRIBUTING.md docs: Fix typos, formatting, and numbering in README.md and CONTRIBUTING.md. 2026-03-23 12:05:24 +01:00
INVIOLABLES.md
Kconfig tools/stackusage.py: use toolchain binaries instead of Python libraries 2026-03-17 11:26:44 -03:00
LICENSE !boards: Remove NSH_ARCHINIT and board_app_initialize 2026-05-02 18:36:46 +08:00
Makefile tools: migrate to SPDX identifier 2024-09-10 23:11:11 +08:00
NOTICE Remove the double blank line from source files 2022-02-20 20:10:14 +01:00
README.md docs: Fix typos, formatting, and numbering in README.md and CONTRIBUTING.md. 2026-03-23 12:05:24 +01:00
ReleaseNotes Documentation: move ReleaseNotes 2023-09-26 20:41:00 +08:00

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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.