unistd: handle required _SC* values in sysconf

[adamgreloch]

Fixes: phoenix-rtos/phoenix-rtos-project#1458

Description

Motivation and Context

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Chore (refactoring, style fixes, git/CI config, submodule management, no code logic changes)

How Has This Been Tested?

• Already covered by automatic testing.
• New test added: (add PR link here).
• Tested by hand on: (list targets here).

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing linter checks and tests passed.
• My changes generate no new compilation warnings for any of the targets.

Special treatment

• This PR needs additional PRs to work (list the PRs, preferably in merge-order).
• I will merge this PR by myself when appropriate.

[gemini-code-assist]

Code Review

This pull request expands the sysconf implementation by defining and adding support for numerous POSIX system configuration constants (_SC_*). It also updates _SC_OPEN_MAX to return -1 for POSIX compliance. The review feedback highlights several areas for improvement: ensuring that limits associated with unsupported options also return -1 to comply with POSIX standards, returning defined limits like NGROUPS_MAX and PTHREAD_DESTRUCTOR_ITERATIONS instead of their POSIX minimums, and adding the missing _SC_CLK_TCK case to the sysconf switch statement.

[github-actions]

Unit Test Results

13 287 tests  ±0   12 469 ✅ ±0   59m 22s ⏱️ +28s
   756 suites ±0      818 💤 ±0 
     1 files   ±0        0 ❌ ±0 

Results for commit 27ef143. ± Comparison against base commit 6a150a2.

[github-actions]

Unit Test Results (nightly)

     1 files   3 182 suites   6h 8m 27s ⏱️
29 115 tests 25 021 ✅ 4 094 💤 0 ❌
29 301 runs  25 168 ✅ 4 133 💤 0 ❌

Results for commit 24ae168.

[adamgreloch]

/gemini review

[gemini-code-assist]

Code Review

This pull request expands POSIX compliance by defining numerous _SC_* configuration constants in include/unistd.h and implementing their handling in sysconf within unistd/conf.c. Additionally, _SC_OPEN_MAX now returns -1 to remain POSIX-compliant. The review feedback suggests improving sysconf by returning the defined PTHREAD_DESTRUCTOR_ITERATIONS and NGROUPS_MAX constants instead of returning -1 or fallback values, respectively.

[gemini-code-assist]

Since PTHREAD_DESTRUCTOR_ITERATIONS is defined in <limits.h> (via <posix/limits.h>), sysconf(_SC_THREAD_DESTRUCTOR_ITERATIONS) should return its value instead of -1 to be POSIX-compliant.

Suggested change

	case _SC_THREAD_DESTRUCTOR_ITERATIONS:
	case _SC_THREAD_KEYS_MAX:
	case _SC_THREAD_STACK_MIN:
	case _SC_THREAD_THREADS_MAX:
	/* The POSIX Threads option is not fully supported. */
	return -1;
	case _SC_THREAD_DESTRUCTOR_ITERATIONS:
	return PTHREAD_DESTRUCTOR_ITERATIONS;
	case _SC_THREAD_KEYS_MAX:
	case _SC_THREAD_STACK_MIN:
	case _SC_THREAD_THREADS_MAX:
	/* The POSIX Threads option is not fully supported. */
	return -1;

[gemini-code-assist]

Since NGROUPS_MAX is defined in <limits.h>, sysconf(_SC_NGROUPS_MAX) should return NGROUPS_MAX instead of the POSIX minimum fallback _POSIX_NGROUPS_MAX. This ensures that any future changes to NGROUPS_MAX are automatically reflected in sysconf.

Suggested change

	case _SC_NGROUPS_MAX:
	return _POSIX_NGROUPS_MAX;
	case _SC_NGROUPS_MAX:
	return NGROUPS_MAX;