libc: Restore prior C23 include guards

To avoid any sort of POLA violation, this commit restores old
guards and defines the C23 feature test macros in addition to
them.  This is to close off whole class of possible breakage,
rather than patching it case by case.

Reported by:	dim
Reviewed by:	dim, dteske, fuz
Approved by:	dim, dteske (mentor), fuz (mentor)
MFC after:	1 month
Differential Revision: https://reviews.freebsd.org/D58911

include/assert.h

@@ -68,8 +68,10 @@
 #endif /* __BSD_VISIBLE */
 #endif /* NDEBUG */
 
-#ifndef __STDC_VERSION_ASSERT_H__
-#define __STDC_VERSION_ASSERT_H__ 202311L
+#ifndef _ASSERT_H_
+#define _ASSERT_H_
+
+#define __STDC_VERSION_ASSERT_H__	202311L
 
 /*
  * Static assertions.  In principle we could define static_assert for
@@ -92,4 +94,4 @@ __BEGIN_DECLS
 void __assert(const char *, const char *, int, const char *) __dead2;
 __END_DECLS
 
-#endif /* !__STDC_VERSION_ASSERT_H__ */
+#endif /* !_ASSERT_H_ */

include/limits.h

@@ -29,7 +29,9 @@
  * SUCH DAMAGE.
  */
 
-#ifndef __STDC_VERSION_LIMITS_H__
+#ifndef _LIMITS_H_
+#define _LIMITS_H_
+
 #define __STDC_VERSION_LIMITS_H__	202311L
 
 #include <sys/cdefs.h>
@@ -148,4 +150,4 @@
 #include <sys/syslimits.h>
 #endif
 
-#endif /* !__STDC_VERSION_LIMITS_H__ */
+#endif /* !_LIMITS_H_ */

include/rpc/xdr.h

@@ -332,7 +332,7 @@ __BEGIN_DECLS
 extern void   xdrmem_create(XDR *, char *, u_int, enum xdr_op);
 
 /* XDR using stdio library */
-#ifdef __STDC_VERSION_STDIO_H__
+#ifdef _STDIO_H_
 extern void   xdrstdio_create(XDR *, FILE *, enum xdr_op);
 #endif
 

include/stdio.h

@@ -32,7 +32,9 @@
  * SUCH DAMAGE.
  */
 
-#ifndef __STDC_VERSION_STDIO_H__
+#ifndef	_STDIO_H_
+#define	_STDIO_H_
+
 #define __STDC_VERSION_STDIO_H__	202311L
 
 #include <sys/cdefs.h>
@@ -540,4 +542,4 @@ extern int __isthreaded;
 __END_DECLS
 __NULLABILITY_PRAGMA_POP
 
-#endif /* !__STDC_VERSION_STDIO_H__ */
+#endif /* !_STDIO_H_ */

include/xlocale.h

@@ -68,7 +68,7 @@ __BEGIN_DECLS
 #include <xlocale/_ctype.h>
 #endif
 
-#ifdef __STDC_VERSION_STDIO_H__
+#ifdef _STDIO_H_
 #include <xlocale/_stdio.h>
 #endif
 

lib/libc/xdr/xdr.3

@@ -572,7 +572,7 @@ This routine returns the amount of memory required to encode
 using filter
 .Fa func .
 .Pp
-.It Li "#ifdef __STDC_VERSION_STDIO_H__"
+.It Li "#ifdef _STDIO_H_"
 .It Li "/* XDR using stdio library */"
 .It Xo
 .Ft void

lib/libgeom/libgeom.h

@@ -143,7 +143,7 @@ void geom_deletetree(struct gmesh *);
 
 struct gctl_req;
 
-#ifdef __STDC_VERSION_STDIO_H__		/* limit #include pollution */
+#ifdef _STDIO_H_			/* limit #include pollution */
 void gctl_dump(struct gctl_req *, FILE *);
 #endif
 void gctl_free(struct gctl_req *);

lib/libutil/libutil.h

@@ -151,7 +151,7 @@ int	uu_lock_txfr(const char *_ttyname, pid_t _pid);
  * Conditionally prototype the following functions if the include
  * files upon which they depend have been included.
  */
-#ifdef __STDC_VERSION_STDIO_H__
+#ifdef _STDIO_H_
 char	*fparseln(FILE *_fp, size_t *_len, size_t *_lineno,
 	    const char _delim[3], int _flags);
 #endif

stand/libsa/geli/geliboot_internal.h

@@ -28,15 +28,9 @@
 #ifndef _GELIBOOT_INTERNAL_H_
 #define _GELIBOOT_INTERNAL_H_
 
-/*
- * XXX:
- * The following deliberate defines are to keep g_eli.h from including
- * unnecessary headers.  It would be preferable to conditionally include
- * them in a _STANDALONE branch there instead.
- */
 #define _STRING_H_
 #define _STRINGS_H_
-#define __STDC_VERSION_STDIO_H__	202311L
+#define _STDIO_H_
 
 #include <sys/endian.h>
 #include <sys/queue.h>

sys/sys/stdatomic.h

@@ -27,7 +27,9 @@
  * SUCH DAMAGE.
  */
 
-#ifndef __STDC_VERSION_STDATOMIC_H__
+#ifndef _STDATOMIC_H_
+#define _STDATOMIC_H_
+
 #define __STDC_VERSION_STDATOMIC_H__	202311L
 
 #include <sys/cdefs.h>
@@ -438,4 +440,4 @@ atomic_flag_clear(volatile atomic_flag *__object)
 #undef __bool_locally_defined
 #endif
 
-#endif /* !__STDC_VERSION_STDATOMIC_H__ */
+#endif /* !_STDATOMIC_H_ */

sys/sys/syslimits.h

@@ -33,7 +33,7 @@
 #define _SYS_SYSLIMITS_H_
 
 #if !defined(_STANDALONE) && !defined(_KERNEL) && \
-    !defined(__STDC_VERSION_LIMITS_H__) && !defined(_SYS_PARAM_H_)
+    !defined(_LIMITS_H_) && !defined(_SYS_PARAM_H_)
 #warning "No user-serviceable parts inside."
 #endif