[PATCH] newlib: fix macro definitions related to POSIX.1-2024

_GNU_SOURCE already causes _POSIX_C_SOURCE to be set to 202405L via the
_DEFAULT_SOURCE logic. Updated the explicit definition of _POSIX_C_SOURCE to
202405L to avoid confusion and make the behavior more explicit.

This commit adds _XOPEN_SOURCE=800 and related visibility macros to align with 
the expected feature set when _GNU_SOURCE is defined. This also enables Single
UNIX Specification v5 (SUSv5) features.

Also improves clarity and future compatibility for applications relying on
recent POSIX/XSI standards.

---
 newlib/libc/include/sys/features.h | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/newlib/libc/include/sys/features.h b/newlib/libc/include/sys/features.h
index 570bdf27a..436b62ae8 100644
--- a/newlib/libc/include/sys/features.h
+++ b/newlib/libc/include/sys/features.h
@@ -132,9 +132,9 @@ extern "C" {
 #undef _POSIX_SOURCE
 #define	_POSIX_SOURCE		1
 #undef _POSIX_C_SOURCE
-#define	_POSIX_C_SOURCE		200809L
+#define	_POSIX_C_SOURCE		202405L
 #undef _XOPEN_SOURCE
-#define	_XOPEN_SOURCE		700
+#define	_XOPEN_SOURCE		800
 #undef _XOPEN_SOURCE_EXTENDED
 #define	_XOPEN_SOURCE_EXTENDED	1
 #endif /* _GNU_SOURCE */
@@ -158,7 +158,9 @@ extern "C" {
   ((!defined(__STRICT_ANSI__) && !defined(_ANSI_SOURCE)) || \
    (_XOPEN_SOURCE - 0) >= 500)
 #define	_POSIX_SOURCE		1
-#if !defined(_XOPEN_SOURCE) || (_XOPEN_SOURCE - 0) >= 700
+#if !defined(_XOPEN_SOURCE) || (_XOPEN_SOURCE - 0) >= 800
+#define	_POSIX_C_SOURCE		202405L
+#elif (_XOPEN_SOURCE - 0) >= 700
 #define	_POSIX_C_SOURCE		200809L
 #elif (_XOPEN_SOURCE - 0) >= 600
 #define	_POSIX_C_SOURCE		200112L
@@ -206,7 +208,7 @@ extern "C" {
  *
  * __POSIX_VISIBLE >= 202405
  *	POSIX.1-2024; enabled by default, with _POSIX_C_SOURCE >= 202405L,
- *	or _XOPEN_SOURCE >= 700.
+ *	or _XOPEN_SOURCE >= 800.
  *
  * __XSI_VISIBLE
  *	XPG4 XSI extensions; enabled with any version of _XOPEN_SOURCE.
@@ -224,6 +226,9 @@ extern "C" {
  * __XSI_VISIBLE >= 700
  *	SUSv4 XSI extensions; enabled with _XOPEN_SOURCE >= 700.
  *
+ * __XSI_VISIBLE >= 800
+ *	SUSv5 XSI extensions; enabled with _XOPEN_SOURCE >= 800.
+ *
  * __ISO_C_VISIBLE >= 1999
  *	ISO C99; enabled with gcc -std=c99 or newer (on by default since GCC 5),
  *	any version of C++, or with _ISOC99_SOURCE, _POSIX_C_SOURCE >= 200112L,
@@ -334,7 +339,9 @@ extern "C" {
 #define	__SVID_VISIBLE		0
 #endif
 
-#if (_XOPEN_SOURCE - 0) >= 700
+#if (_XOPEN_SOURCE - 0) >= 800
+#define	__XSI_VISIBLE		800
+#elif (_XOPEN_SOURCE - 0) >= 700
 #define	__XSI_VISIBLE		700
 #elif (_XOPEN_SOURCE - 0) >= 600
 #define	__XSI_VISIBLE		600
-- 
2.43.0