sim: posix: add platform-specific timer handling for macOS and Linux by aditya0yadav · Pull Request #18331 · apache/nuttx

aditya0yadav · 2026-02-03T07:15:08Z

PLEASE DONT MERGE THIS PR

Summary

This change updates the POSIX simulator host timer implementation to
handle platform differences between macOS (Darwin) and Linux.

macOS does not provide full support for POSIX timers such as
timer_create() and timer_settime(). To address this, the simulator
now uses setitimer() on macOS while retaining POSIX timers with
absolute-time scheduling on Linux and other POSIX systems.

The platform selection is handled via the NUTTX_DARWIN macro, keeping
the simulator core logic unchanged while improving portability and
correctness on macOS.

Impact

Improves portability of the POSIX simulator on macOS hosts.
No functional or behavioral change for Linux or other POSIX platforms.
No impact on target hardware, board support, or NuttX core logic.
No documentation or security impact.
Build behavior remains unchanged on supported Linux systems.

Testing

Tested on macOS (Darwin):
- Host: macOS (Apple Silicon)
- Simulator: POSIX SIM
- Verified successful build and runtime execution.
- Confirmed timer interrupts are delivered via SIGALRM and simulator
  scheduling behaves as expected.
Linux testing:
- Not yet tested on a Linux host.

Since this change affects host timer handling, additional testing on
Linux systems would be valuable before merging.
If anyone is able to test this change on a Linux PC and confirm that the
POSIX simulator builds and runs correctly, that feedback and any logs
would be greatly appreciated.

One more thing ,
For supporting macos, multiple things need to be done like docs and linker too .

aditya0yadav · 2026-02-03T07:17:00Z

For macos,
Please disable this
COVERAGE_TOOLCHAIN(=n) "Link toolchain gcov library to the OS"
SYSTEM_GCOV(=n) "gcov tool"

simbit18 · 2026-02-03T10:39:58Z

Hi @aditya0yadav , I converted PR into draft.

@FelipeMdeO @lupyuen @aviralgarg05 What do you think?
#17818

xiaoxiang781216 · 2026-02-03T11:17:43Z

arch/sim/src/sim/posix/sim_hosttime.c

+  it.it_interval.tv_sec  = 0;
+  it.it_interval.tv_usec = 0;
+
+  return setitimer(ITIMER_REAL, &it, NULL);


why not use setitimer on Linux too? https://linux.die.net/man/2/setitimer

Because linux has a better api : timer_create() + timer_settime()
in macos , we have to use that time_create exist but unreliable and uncompleted and time_settime() is not properly supported

it's better to go the same code path if we can, so don't need double the test effort.

@xiaoxiang781216 Ok i will do that
Any suggestion about linker
for to use sim in macos , we need to disable the gcov

@xiaoxiang781216 now set timer is being shared bet linux and macOS

jerpelea · 2026-02-03T12:54:56Z

please remove the merge commit !

aviralgarg05 · 2026-02-03T12:57:25Z

Hi @aditya0yadav , I converted PR into draft.

@FelipeMdeO @lupyuen @aviralgarg05 What do you think? #17818

Hi @simbit18, thanks for tagging me, the core approach of using setitimer() for macOS makes sense as a workaround for the missing POSIX timers but the addition of #define _POSIX_C_SOURCE 200809L in sim_hosttime.c has broken the Linux build. It causes an implicit declaration error for usleep() because usleep was removed in POSIX 2008. We might need to keep _POSIX_C_SOURCE at an older version or switch usleep to nanosleep.

and remove the use of #define _POSIX_C_SOURCE 200809L

simbit18 · 2026-02-04T12:03:37Z

arch/sim/src/sim/posix/sim_hosttime.c

@@ -1,5 +1,7 @@
 /****************************************************************************
- * arch/sim/src/sim/posix/sim_hosttime.c
+ * arch/sim/src/sim/win/sim_hosttime.c


@aditya0yadav incorrect path

@simbit18
by mistake i copied license header from win folder

aditya0yadav · 2026-02-04T12:04:31Z

@aviralgarg05 I’ve removed the #define _POSIX_C_SOURCE 200809L in macOS and Ubuntu-based code spaces and it’s working properly. Mind taking a look?

aditya0yadav · 2026-02-04T12:10:43Z

@simbit18 One more thing, what should we do with the linker in macOS?
I know it will work perfectly with Linux but not with macOS.

Every time I have to disable the configuration toolchain related to Gcov.

Any suggestions?

aviralgarg05 · 2026-02-04T13:52:11Z

@aviralgarg05 I’ve removed the #define _POSIX_C_SOURCE 200809L in macOS and Ubuntu-based code spaces and it’s working properly. Mind taking a look?

Thanks for the update @aditya0yadav, I checked the latest changes, the approach looks correct. There might be an issue with the setitimer tick scheduling - the simulator isn't booting correctly. Could you check if SIGALRM is being delivered properly?

aditya0yadav · 2026-02-04T13:53:26Z

Thanks for the review, @aviralgarg05. I will look into it .

simbit18 · 2026-02-04T14:36:33Z

@simbit18 One more thing, what should we do with the linker in macOS? I know it will work perfectly with Linux but not with macOS.

Every time I have to disable the configuration toolchain related to Gcov.

Any suggestions?

A long time ago, it was possible to build sim:nsh for Linux, macOS, and Windows .
Currently, it does not work on macOS and Windows with MSYS2/Cygwin (the latest version I was able to build and test was 10.2), so I personally think it is right to restore the build by modifying the defconfig file.

Of course, this is just my opinion! :)

acassis · 2026-02-04T14:50:13Z

@simbit18 One more thing, what should we do with the linker in macOS? I know it will work perfectly with Linux but not with macOS.
Every time I have to disable the configuration toolchain related to Gcov.
Any suggestions?

A long time ago, it was possible to build sim:nsh for Linux, macOS, and Windows . Currently, it does not work on macOS and Windows with MSYS2/Cygwin (the latest version I was able to build and test was 10.2), so I personally think it is right to restore the build by modifying the defconfig file.

Of course, this is just my opinion! :)

I think is makes sense, maybe using git bisect it could be possible to identify which symbols cases the breaking and open an issue to track it.

simbit18 · 2026-02-05T10:45:32Z

Hi @raiden00pl, The changes in this PR cause errors in sim:citest. Can you check it?

Traceback (most recent call last):
YAML config:
  File "/usr/lib/python3.10/runpy.py", line 196, in _run_module_as_main
{'config': {'cwd': './', 'timeout_session': 6000},
 'product': {'cores': {'core0': {'conf_path': './.config',
                                 'device': 'sim',
                                 'elf_path': './nuttx',
                                 'name': 'main'}},
             'name': 'ntfc-sim'}}
JSON config:
{'args': {'kv': []},
 'module': {'exclude_module': ['Nuttx_System_Driver_Pm', 'Nuttx_System_Fs_Fs'],
            'include_module': [],
            'order': []}}
    return _run_code(code, main_globals, None,
  File "/usr/lib/python3.10/runpy.py", line 86, in _run_code
    exec(code, run_globals)
  File "/github/workspace/nuttx-ntfc/venv/lib/python3.10/site-packages/ntfc/__main__.py", line 25, in <module>
    main()  # pylint: disable=no-value-for-parameter
  File "/github/workspace/nuttx-ntfc/venv/lib/python3.10/site-packages/click/core.py", line 1485, in __call__
    return self.main(*args, **kwargs)
  File "/github/workspace/nuttx-ntfc/venv/lib/python3.10/site-packages/click/core.py", line 1416, in main
    ctx.exit()
  File "/github/workspace/nuttx-ntfc/venv/lib/python3.10/site-packages/click/core.py", line 737, in exit
    self.close()
  File "/github/workspace/nuttx-ntfc/venv/lib/python3.10/site-packages/click/core.py", line 621, in close
    self._close_with_exception_info(None, None, None)
  File "/github/workspace/nuttx-ntfc/venv/lib/python3.10/site-packages/click/core.py", line 635, in _close_with_exception_info
    exit_result = self._exit_stack.__exit__(exc_type, exc_value, tb)
  File "/usr/lib/python3.10/contextlib.py", line 576, in __exit__
    raise exc_details[1]
  File "/usr/lib/python3.10/contextlib.py", line 561, in __exit__
    if cb(*exc_details):
  File "/usr/lib/python3.10/contextlib.py", line 449, in _exit_wrapper
    callback(*args, **kwds)
  File "/github/workspace/nuttx-ntfc/venv/lib/python3.10/site-packages/click/decorators.py", line 93, in new_func
    return ctx.invoke(f, obj, *args, **kwargs)
  File "/github/workspace/nuttx-ntfc/venv/lib/python3.10/site-packages/click/core.py", line 824, in invoke
    return callback(*args, **kwargs)
  File "/github/workspace/nuttx-ntfc/venv/lib/python3.10/site-packages/ntfc/cli/main.py", line 181, in cli_on_close
    ret = test_run(pt, ctx)
  File "/github/workspace/nuttx-ntfc/venv/lib/python3.10/site-packages/ntfc/cli/main.py", line 123, in test_run
    return pt.runner(ctx.testpath, ctx.result, ctx.nologs)
  File "/github/workspace/nuttx-ntfc/venv/lib/python3.10/site-packages/ntfc/pytest/mypytest.py", line 270, in runner
    self._device_start()
  File "/github/workspace/nuttx-ntfc/venv/lib/python3.10/site-packages/ntfc/pytest/mypytest.py", line 222, in _device_start
    product.start()
  File "/github/workspace/nuttx-ntfc/venv/lib/python3.10/site-packages/ntfc/product.py", line 70, in start
    self._cores.start()
  File "/github/workspace/nuttx-ntfc/venv/lib/python3.10/site-packages/ntfc/cores.py", line 73, in start
    core.start()
  File "/github/workspace/nuttx-ntfc/venv/lib/python3.10/site-packages/ntfc/core.py", line 510, in start
    self._device.start()
  File "/github/workspace/nuttx-ntfc/venv/lib/python3.10/site-packages/ntfc/device/sim.py", line 52, in start
    self.host_open(cmd, uptime)
  File "/github/workspace/nuttx-ntfc/venv/lib/python3.10/site-packages/ntfc/device/host.py", line 139, in host_open
    raise TimeoutError("device boot timeout")
TimeoutError: device boot timeout
+ ret=1
+ echo 1
+ deactivate

raiden00pl · 2026-02-05T11:12:15Z

@simbit18 @aditya0yadav sim/citest is broken, NTFC detects that device is broken at init or doesn't boot at all.

When I run binary from this PR, NSH is not functional and it stucks on NSH prompt (not sure what is this init error and if it's realted):

probably not everyone knows about it, but you can download built binaries directly from CI:

raiden00pl · 2026-02-05T11:37:35Z

with this PR sim/citest compiled on my host doesn't work either but sim/nsh works fine

simbit18 · 2026-02-05T11:48:21Z

@raiden00pl, thank you very much.

aditya0yadav · 2026-02-05T22:04:15Z

@simbit18 One more thing, what should we do with the linker in macOS? I know it will work perfectly with Linux but not with macOS.
Every time I have to disable the configuration toolchain related to Gcov.
Any suggestions?

A long time ago, it was possible to build sim:nsh for Linux, macOS, and Windows . Currently, it does not work on macOS and Windows with MSYS2/Cygwin (the latest version I was able to build and test was 10.2), so I personally think it is right to restore the build by modifying the defconfig file.
Of course, this is just my opinion! :)

I think is makes sense, maybe using git bisect it could be possible to identify which symbols cases the breaking and open an issue to track it.

I just want to check if I’m understanding correctly:
@simbit18 @acassis

The linker issue seems to happen only on macOS, not on Linux. On Linux, it works fine and uses Gcov as expected, but on macOS, I always have to disable the Gcov-related toolchain in the configuration.

If I wanted to find the specific symbol that is causing the linker to fail, doing a git bisect over 2–4 years of changes seems impractical because there’s been too much change in the repository.

One idea I had is to use Docker with Linux to build NuttX, since Linux doesn’t hit the macOS linker problem. But of course, that wouldn’t reproduce the macOS-specific issue.

Do you have any suggestions on how to approach this efficiently for macOS?

FelipeMdeO · 2026-02-05T23:31:46Z

Hello all, Sorry for late reply. I am very busy during this week but this weekend I will be available to help. Let me try execute de bisec and find the valid commit. *Felipe Moura de Oliveira* *Universidade Federal de Minas Gerais* Linkedin <https://www.linkedin.com/in/felipe-oliveira-75a651a0> <https://twitter.com/FelipeMOliveir?lang=pt-br>

…

On Thu, 5 Feb 2026 at 19:04 Aditya Yadav ***@***.***> wrote: *aditya0yadav* left a comment (apache/nuttx#18331) <#18331 (comment)> @simbit18 <https://github.com/simbit18> One more thing, what should we do with the linker in macOS? I know it will work perfectly with Linux but not with macOS. Every time I have to disable the configuration toolchain related to Gcov. Any suggestions? A long time ago, it was possible to build sim:nsh for Linux, macOS, and Windows . Currently, it does not work on macOS and Windows with MSYS2/Cygwin (the latest version I was able to build and test was 10.2 <https://github.com/simbit18/nuttx-msys2>), so I personally think it is right to restore the build by modifying the defconfig file. Of course, this is just my opinion! :) I think is makes sense, maybe using git bisect it could be possible to identify which symbols cases the breaking and open an issue to track it. I just want to check if I’m understanding correctly: @simbit18 <https://github.com/simbit18> @acassis <https://github.com/acassis> The linker issue seems to happen only on macOS, not on Linux. On Linux, it works fine and uses Gcov as expected, but on macOS, I always have to disable the Gcov-related toolchain in the configuration. If I wanted to find the specific symbol that is causing the linker to fail, doing a git bisect over 2–4 years of changes seems impractical because there’s been too much change in the repository. One idea I had is to use Docker with Linux to build NuttX, since Linux doesn’t hit the macOS linker problem. But of course, that wouldn’t reproduce the macOS-specific issue. Do you have any suggestions on how to approach this efficiently for macOS? — Reply to this email directly, view it on GitHub <#18331 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ADNC5ZRBKU6VDMZIY5VHU634KO47NAVCNFSM6AAAAACTY7CVNWVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTQNJWGUZDMOBSHE> . You are receiving this because you were mentioned.Message ID: ***@***.***>

aditya0yadav and others added 2 commits February 3, 2026 12:36

sim: posix: use setitimer on Darwin, POSIX timers on Linux

5f6e8b2

Merge branch 'apache:master' into master

151aaeb

aditya0yadav requested review from GUIDINGLI, jerpelea and xiaoxiang781216 as code owners February 3, 2026 07:15

github-actions bot added Arch: simulator Issues related to the SIMulator Size: S The size of the change in this PR is small labels Feb 3, 2026

simbit18 requested review from acassis, lupyuen, pkarashchenko and yamt February 3, 2026 10:31

simbit18 marked this pull request as draft February 3, 2026 10:33

xiaoxiang781216 reviewed Feb 3, 2026

View reviewed changes

now setimer is shared between linux and macos

d82561b

and remove the use of #define _POSIX_C_SOURCE 200809L

simbit18 reviewed Feb 4, 2026

View reviewed changes

fix the word problem

6603580

simbit18 requested a review from raiden00pl February 5, 2026 10:45

Conversation

aditya0yadav commented Feb 3, 2026

PLEASE DONT MERGE THIS PR

Summary

Impact

Testing

Uh oh!

aditya0yadav commented Feb 3, 2026

Uh oh!

simbit18 commented Feb 3, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

xiaoxiang781216 Feb 3, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

aditya0yadav Feb 3, 2026

Choose a reason for hiding this comment

Uh oh!

xiaoxiang781216 Feb 3, 2026

Choose a reason for hiding this comment

Uh oh!

aditya0yadav Feb 3, 2026

Choose a reason for hiding this comment

Uh oh!

aditya0yadav Feb 4, 2026

Choose a reason for hiding this comment

Uh oh!

jerpelea commented Feb 3, 2026

Uh oh!

aviralgarg05 commented Feb 3, 2026

Uh oh!

simbit18 Feb 4, 2026

Choose a reason for hiding this comment

Uh oh!

aditya0yadav Feb 4, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

aditya0yadav commented Feb 4, 2026

Uh oh!

aditya0yadav commented Feb 4, 2026

Uh oh!

aviralgarg05 commented Feb 4, 2026

Uh oh!

aditya0yadav commented Feb 4, 2026 via email • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

simbit18 commented Feb 4, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

acassis commented Feb 4, 2026

Uh oh!

simbit18 commented Feb 5, 2026

Uh oh!

raiden00pl commented Feb 5, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

raiden00pl commented Feb 5, 2026

Uh oh!

simbit18 commented Feb 5, 2026

Uh oh!

aditya0yadav commented Feb 5, 2026

Uh oh!

FelipeMdeO commented Feb 5, 2026 via email

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

8 participants

simbit18 commented Feb 3, 2026 •

edited

Loading

xiaoxiang781216 Feb 3, 2026 •

edited

Loading

aditya0yadav Feb 4, 2026 •

edited

Loading

aditya0yadav commented Feb 4, 2026 via email •

edited

Loading

simbit18 commented Feb 4, 2026 •

edited

Loading

raiden00pl commented Feb 5, 2026 •

edited

Loading