[casaroli]

Summary

This PR makes the POSIX option macros of <unistd.h> and some limits of <limits.h> tell the truth about the configuration, and makes key destructors repeat as POSIX requires.

• include/unistd.h: Make the POSIX option macros follow the configuration. <unistd.h> defined _POSIX_SEMAPHORES, _POSIX_SHARED_MEMORY_OBJECTS, _POSIX_MAPPED_FILES, _POSIX_MESSAGE_PASSING, _POSIX_THREADS, _POSIX_THREAD_PROCESS_SHARED, _POSIX_CPUTIME and _POSIX_THREAD_CPUTIME in every configuration. A program that tests them then used functions that the build does not have: sem_open() needs CONFIG_FS_NAMED_SEMAPHORES, shm_open() needs CONFIG_FS_SHMFS, mmap() of a regular file needs CONFIG_FS_RAMMAP, and the CPU-time clocks need the run-time accounting of CONFIG_SCHED_CRITMONITOR. It did not define _POSIX_BARRIERS, _POSIX_READER_WRITER_LOCKS, _POSIX_SPIN_LOCKS and _POSIX_THREAD_ATTR_STACKADDR, although the functions exist. Now each option is _POSIX_VERSION when the configuration has it, and -1 when it does not. A kernel build has process-shared mutexes only with memory that two processes can share (CONFIG_FS_SHMFS or CONFIG_MM_SHM). The empty _POSIX_THREADS and _POSIX_THREAD_ATTR_STACKSIZE fallbacks in <pthread.h> go (<pthread.h> includes <unistd.h> first, so they never took effect).
• Documentation/standards: Name the options that POSIX option macros need. posix.rst gives the Kconfig option of each of these macros.
• include/limits.h: Define _POSIX_THREAD_KEYS_MAX as the POSIX constant. _POSIX_THREAD_KEYS_MAX is the smallest PTHREAD_KEYS_MAX that POSIX allows, always 128. <limits.h> defined it from CONFIG_TLS_NELEM (0 by default). Now it is 128; PTHREAD_KEYS_MAX still follows CONFIG_TLS_NELEM, and the Kconfig help says that POSIX requires at least 128 keys and what each key costs.
• libs/libc/tls: Repeat the key destructors as POSIX requires. tls_destruct() called each key destructor once and cleared the value after the call, so a value that a destructor set again was lost. Now the value is cleared before the call, and the pass repeats while a destructor ran, up to PTHREAD_DESTRUCTOR_ITERATIONS (4, the POSIX minimum, new in <limits.h>) times.
• include/limits.h: Define LOGIN_NAME_MAX. POSIX requires it. It is NAME_MAX + 1 (getlogin() returns at most NAME_MAX bytes), and the getlogin() buffer uses it.
• Documentation: Describe the destructors of pthread keys. 08_pthread.rst said that the destructor argument of pthread_key_create() is ignored.

Impact

Possible breaking change (source level, every build mode, flat too): the values of these option macros change. An option that the configuration does not have is now -1:

Macro	-1 when
_POSIX_SEMAPHORES	no CONFIG_FS_NAMED_SEMAPHORES
_POSIX_SHARED_MEMORY_OBJECTS	no CONFIG_FS_SHMFS
_POSIX_MAPPED_FILES	no CONFIG_FS_RAMMAP
_POSIX_CPUTIME, _POSIX_THREAD_CPUTIME	no CONFIG_SCHED_CRITMONITOR
_POSIX_MESSAGE_PASSING	CONFIG_DISABLE_MQUEUE
_POSIX_SPIN_LOCKS (new)	no CONFIG_PTHREAD_SPINLOCKS
_POSIX_THREAD_PROCESS_SHARED	kernel build without CONFIG_FS_SHMFS and CONFIG_MM_SHM
_POSIX_THREADS, _POSIX_THREAD_PRIORITY_SCHEDULING, _POSIX_THREAD_ATTR_STACKADDR (new), _POSIX_THREAD_ATTR_STACKSIZE, _POSIX_BARRIERS (new), _POSIX_READER_WRITER_LOCKS (new)	CONFIG_DISABLE_PTHREAD

A program that only tests #ifdef sees no difference. A program that tests the value (#if _POSIX_SEMAPHORES > 0) now takes its fallback when the function is missing; before, it did not link or failed at run time. sysconf(_SC_CPUTIME) and sysconf(_SC_THREAD_CPUTIME) return -1 without CONFIG_SCHED_CRITMONITOR (before: 201712L, while clock_gettime() of these clocks failed with EINVAL).

In-tree users: no C code in nuttx or nuttx-apps tests these macros. lib_sysconf.c returns _POSIX_CPUTIME/_POSIX_THREAD_CPUTIME (see above). The lely-canopen patch in nuttx-apps already excludes NuttX from its _POSIX_MAPPED_FILES paths. getlogin() keeps its buffer size.

<limits.h>: _POSIX_THREAD_KEYS_MAX is 128 in every configuration (was CONFIG_TLS_NELEM); LOGIN_NAME_MAX and PTHREAD_DESTRUCTOR_ITERATIONS are new.

Key destructors: a destructor that sets a value again is called again (at most 4 passes), and a destructor sees its key with the value NULL. In-tree users of pthread_key_create() (ostest, the sim SMP code) give no destructor. Task-local storage (task_tls_alloc()) is not changed.

No size change of a structure. No new Kconfig option.

Testing

Test programs posixopts.c (each option macro must match what the build can do) and limitsposix.c, on qemu-armv8a:knsh (kernel build) and qemu-armv8a:nsh (flat build, the tests as builtin apps), QEMU with HVF, CONFIG_TLS_NELEM=8:

Case	master	this PR
_POSIX_BARRIERS, _POSIX_READER_WRITER_LOCKS, _POSIX_SPIN_LOCKS defined; barriers and rwlocks work	not defined: FAIL	201712L, 201712L, -1: PASS
_POSIX_THREAD_ATTR_STACKSIZE/STACKADDR have a value	empty / not defined: FAIL	201712L: PASS
_POSIX_MAPPED_FILES matches mmap() of a file	201712L, mmap() fails: FAIL	-1: PASS
_POSIX_SEMAPHORES matches sem_open() (default)	201712L, no sem_open(): FAIL	-1: PASS
the same with CONFIG_FS_NAMED_SEMAPHORES (knsh)	PASS	201712L: PASS
_POSIX_THREAD_PROCESS_SHARED: a process-shared mutex and condition variable work across two tasks in shm_open() memory (knsh; flat with CONFIG_FS_SHMFS)	PASS	PASS
_POSIX_THREAD_KEYS_MAX == 128	8: FAIL	128: PASS
LOGIN_NAME_MAX defined, >= 9	not defined: FAIL	33: PASS
PTHREAD_DESTRUCTOR_ITERATIONS defined, >= 4	not defined: FAIL	4: PASS
a destructor that sets the value again is called again, and sees NULL	1 call: FAIL	3 calls, NULL each time: PASS

The results are the same on knsh and on flat nsh. ostest exits with status 0 on qemu-armv8a:knsh and qemu-armv8a:nsh (also in the flat runs with the test apps), on master and with this PR.

Build, each OK: qemu-armv8a:nsh (flat, arm64), also with CONFIG_FS_RAMMAP and CONFIG_SCHED_CRITMONITOR; qemu-armv8a:knsh (kernel, arm64), also with CONFIG_FS_NAMED_SEMAPHORES, CONFIG_PTHREAD_SPINLOCKS and CONFIG_MM_SHM; rv-virt:knsh64 (kernel, rv64); mps2-an500:nsh (flat, Cortex-M7), also with CONFIG_DISABLE_PTHREAD (without the ostest and getprime apps, which need pthreads, as on master); mps2-an500:knsh (protected, Cortex-M7).

tools/checkpatch.sh -c -u -m -g passes.

[github-actions]

MemBrowse Memory Report · Explore what changed →

No memory changes detected for:

• arduino-mega2560
• esp32-devkitc
• hifive1-revb
• mirtoo
• qemu-armv8a
• qemu-intel64
• rx65n-rsk2mb
• s698pm-dkit
• stm32-nucleo-f103rb

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[xiaoxiang781216]

please fix ci error, @casaroli

[casaroli]

The arm-ti failure is on master: lm3s6965-ek:qemu-flat overflows by 212 bytes and qemu-protected by 280 bytes without this PR. #21219 and #21321 fix them.