posix: sysconf: declare sysconf macro values more reliably

The `sysconf()` implementation in Zephyr can be macro-based or
library-based. Both approaches use the same set of runtime-invariant
definitions in `sys/sysconf.h`.

These were previously fine, as long as POSIX limits were
guaranteed to be defined. However, some C libraries omit definitions
for runtime-invariants values and instead force the application to
query values via `sysconf()`.

The specification formally supports that approach [1]. Normally,
definitions are allowed to do so "on specific implementations where the
corresponding value is equal to or greater than the stated minimum, but
is unspecified." In practice, that is not always the case, but we need
to be able to compile `sysconf()` anyway.

Notable constants that are missing in Picolibc or Newlib include:

- AIO_LISTIO_MAX
- AIO_MAX
- AIO_PRIO_DELTA_MAX
- CHILD_MAX
- DELAYTIMER_MAX
- HOST_NAME_MAX
- IOV_MAX
- LOGIN_NAME_MAX
- MQ_OPEN_MAX
- MQ_PRIO_MAX
- OPEN_MAX
- PAGESIZE
- PAGE_SIZE
- PTHREAD_DESTRUCTOR_ITERATIONS
- PTHREAD_KEYS_MAX
- PTHREAD_THREADS_MAX
- RTSIG_MAX
- SEM_NSEMS_MAX
- SEM_VALUE_MAX
- SIGQUEUE_MAX
- SS_REPL_MAX
- STREAM_MAX
- SYMLOOP_MAX
- TIMER_MAX
- TTY_NAME_MAX

For greater portability, define those values using

1. a Kconfig-derived definition,
2. a symbolic minimum value (required by the spec), or
3. a numeric minimum value (if the required symbolic minimum is missing).

[1]
https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/limits.h.html

Signed-off-by: Chris Friedt <[email protected]>

Author: cfriedt

include/zephyr/posix/sys/sysconf.h

@@ -7,6 +7,8 @@
 #ifndef ZEPHYR_INCLUDE_POSIX_SYS_SYSCONF_H_
 #define ZEPHYR_INCLUDE_POSIX_SYS_SYSCONF_H_
 
+#include <limits.h>
+
 #include <zephyr/sys/util_macro.h>
 
 #ifdef __cplusplus
@@ -244,7 +246,8 @@ enum {
 	COND_CODE_1(_POSIX2_C_DEV > 0, (_POSIX2_C_DEV), (-1))
 #define __z_posix_sysconf_SC_2_CHAR_TERM                  (-1L)
 #define __z_posix_sysconf_SC_COLL_WEIGHTS_MAX             _POSIX2_COLL_WEIGHTS_MAX
-#define __z_posix_sysconf_SC_DELAYTIMER_MAX               _POSIX_DELAYTIMER_MAX
+#define __z_posix_sysconf_SC_DELAYTIMER_MAX                                                        \
+	COND_CODE_1(CONFIG_POSIX_TIMERS, (CONFIG_POSIX_DELAYTIMER_MAX), (0))
 #define __z_posix_sysconf_SC_EXPR_NEST_MAX                _POSIX2_EXPR_NEST_MAX
 #define __z_posix_sysconf_SC_2_FORT_DEV                   (-1L)
 #define __z_posix_sysconf_SC_2_FORT_RUN                   (-1L)
@@ -273,34 +276,42 @@ enum {
 #define __z_posix_sysconf_SC_CLK_TCK                      (100L)
 #define __z_posix_sysconf_SC_GETGR_R_SIZE_MAX             (0L)
 #define __z_posix_sysconf_SC_GETPW_R_SIZE_MAX             (0L)
-#define __z_posix_sysconf_SC_AIO_LISTIO_MAX               AIO_LISTIO_MAX
-#define __z_posix_sysconf_SC_AIO_MAX                      AIO_MAX
-#define __z_posix_sysconf_SC_AIO_PRIO_DELTA_MAX           AIO_PRIO_DELTA_MAX
-#define __z_posix_sysconf_SC_ARG_MAX                      ARG_MAX
-#define __z_posix_sysconf_SC_ATEXIT_MAX                   ATEXIT_MAX
-#define __z_posix_sysconf_SC_CHILD_MAX                    CHILD_MAX
-#define __z_posix_sysconf_SC_HOST_NAME_MAX                HOST_NAME_MAX
-#define __z_posix_sysconf_SC_IOV_MAX                      IOV_MAX
-#define __z_posix_sysconf_SC_LOGIN_NAME_MAX               LOGIN_NAME_MAX
+#define __z_posix_sysconf_SC_AIO_LISTIO_MAX               _POSIX_AIO_LISTIO_MAX
+#define __z_posix_sysconf_SC_AIO_MAX                      _POSIX_AIO_MAX
+#define __z_posix_sysconf_SC_AIO_PRIO_DELTA_MAX           0
+#define __z_posix_sysconf_SC_ARG_MAX                      _POSIX_ARG_MAX
+#define __z_posix_sysconf_SC_ATEXIT_MAX                   32
+#define __z_posix_sysconf_SC_CHILD_MAX                    _POSIX_CHILD_MAX
+#define __z_posix_sysconf_SC_HOST_NAME_MAX                                                         \
+	COND_CODE_1(CONFIG_POSIX_NETWORKING, (CONFIG_POSIX_HOST_NAME_MAX), (0))
+#define __z_posix_sysconf_SC_IOV_MAX                      16 /* _XOPEN_IOV_MAX */
+#define __z_posix_sysconf_SC_LOGIN_NAME_MAX               _POSIX_LOGIN_NAME_MAX
 #define __z_posix_sysconf_SC_NGROUPS_MAX                  _POSIX_NGROUPS_MAX
-#define __z_posix_sysconf_SC_MQ_OPEN_MAX                  MQ_OPEN_MAX
-#define __z_posix_sysconf_SC_MQ_PRIO_MAX                  MQ_PRIO_MAX
-#define __z_posix_sysconf_SC_OPEN_MAX                     CONFIG_ZVFS_OPEN_MAX
-#define __z_posix_sysconf_SC_PAGE_SIZE                    PAGE_SIZE
-#define __z_posix_sysconf_SC_PAGESIZE                     PAGESIZE
-#define __z_posix_sysconf_SC_THREAD_DESTRUCTOR_ITERATIONS PTHREAD_DESTRUCTOR_ITERATIONS
-#define __z_posix_sysconf_SC_THREAD_KEYS_MAX              PTHREAD_KEYS_MAX
-#define __z_posix_sysconf_SC_THREAD_STACK_MIN             PTHREAD_STACK_MIN
-#define __z_posix_sysconf_SC_THREAD_THREADS_MAX           PTHREAD_THREADS_MAX
-#define __z_posix_sysconf_SC_RTSIG_MAX                    RTSIG_MAX
-#define __z_posix_sysconf_SC_SEM_NSEMS_MAX                SEM_NSEMS_MAX
-#define __z_posix_sysconf_SC_SEM_VALUE_MAX                SEM_VALUE_MAX
-#define __z_posix_sysconf_SC_SIGQUEUE_MAX                 SIGQUEUE_MAX
-#define __z_posix_sysconf_SC_STREAM_MAX                   STREAM_MAX
-#define __z_posix_sysconf_SC_SYMLOOP_MAX                  SYMLOOP_MAX
-#define __z_posix_sysconf_SC_TIMER_MAX                    TIMER_MAX
-#define __z_posix_sysconf_SC_TTY_NAME_MAX                 TTY_NAME_MAX
-#define __z_posix_sysconf_SC_TZNAME_MAX                   TZNAME_MAX
+#define __z_posix_sysconf_SC_MQ_OPEN_MAX                                                           \
+	COND_CODE_1(CONFIG_POSIX_MESSAGE_PASSING, (CONFIG_POSIX_MQ_OPEN_MAX), (0))
+#define __z_posix_sysconf_SC_MQ_PRIO_MAX                  _POSIX_MQ_PRIO_MAX
+#define __z_posix_sysconf_SC_OPEN_MAX                     CONFIG_POSIX_OPEN_MAX
+#define __z_posix_sysconf_SC_PAGE_SIZE                    CONFIG_POSIX_PAGE_SIZE
+#define __z_posix_sysconf_SC_PAGESIZE                     CONFIG_POSIX_PAGE_SIZE
+#define __z_posix_sysconf_SC_THREAD_DESTRUCTOR_ITERATIONS _POSIX_THREAD_DESTRUCTOR_ITERATIONS
+#define __z_posix_sysconf_SC_THREAD_KEYS_MAX                                                       \
+	COND_CODE_1(CONFIG_POSIX_THREADS, (CONFIG_POSIX_THREAD_KEYS_MAX), (0))
+#define __z_posix_sysconf_SC_THREAD_STACK_MIN             0
+#define __z_posix_sysconf_SC_THREAD_THREADS_MAX                                                    \
+	COND_CODE_1(CONFIG_POSIX_THREADS, (CONFIG_POSIX_THREAD_THREADS_MAX), (0))
+#define __z_posix_sysconf_SC_RTSIG_MAX                                                             \
+	COND_CODE_1(CONFIG_POSIX_REALTIME_SIGNALS, (CONFIG_POSIX_RTSIG_MAX), (0))
+#define __z_posix_sysconf_SC_SEM_NSEMS_MAX                                                         \
+	COND_CODE_1(CONFIG_POSIX_SEMAPHORES, (CONFIG_POSIX_SEM_NSEMS_MAX), (0))
+#define __z_posix_sysconf_SC_SEM_VALUE_MAX                                                         \
+	COND_CODE_1(CONFIG_POSIX_SEMAPHORES, (CONFIG_POSIX_SEM_VALUE_MAX), (0))
+#define __z_posix_sysconf_SC_SIGQUEUE_MAX                 _POSIX_SIGQUEUE_MAX
+#define __z_posix_sysconf_SC_STREAM_MAX                   _POSIX_STREAM_MAX
+#define __z_posix_sysconf_SC_SYMLOOP_MAX                  _POSIX_SYMLOOP_MAX
+#define __z_posix_sysconf_SC_TIMER_MAX                                                             \
+	COND_CODE_1(CONFIG_POSIX_TIMERS, (CONFIG_POSIX_TIMER_MAX), (0))
+#define __z_posix_sysconf_SC_TTY_NAME_MAX                 _POSIX_TTY_NAME_MAX
+#define __z_posix_sysconf_SC_TZNAME_MAX                   _POSIX_TZNAME_MAX
 
 #ifdef CONFIG_POSIX_SYSCONF_IMPL_MACRO
 #define sysconf(x) (long)CONCAT(__z_posix_sysconf, x)