[newlib-cygwin/main] sys/cdefs.h: introduce __restrict_arr, as in glibc

[Corinna Vinschen <corinna@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=e66c63be6b800ae19ff21fe2f5c12e231986acb6

commit e66c63be6b800ae19ff21fe2f5c12e231986acb6
Author:     Corinna Vinschen <corinna@vinschen.de>
AuthorDate: Mon Aug 7 15:59:42 2023 +0200
Commit:     Corinna Vinschen <corinna@vinschen.de>
CommitDate: Mon Aug 7 15:59:42 2023 +0200

    sys/cdefs.h: introduce __restrict_arr, as in glibc
    
    C99 allows to define arrays as non-overlappiung using the restrict
    keyword.  This is supported by GCC 3.1 and later, but it's not
    allowed in C++.
    
    This is in preparation of fixing a Cygwin build problem introduce by
    commit 3c75fac130b5.
    
    Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

Diff:
---
 newlib/libc/include/sys/cdefs.h | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/newlib/libc/include/sys/cdefs.h b/newlib/libc/include/sys/cdefs.h
index cc1a8a1ccbf5..d13a92a79ee1 100644
--- a/newlib/libc/include/sys/cdefs.h
+++ b/newlib/libc/include/sys/cdefs.h
@@ -423,6 +423,19 @@
 #define	__restrict
 #endif
 
+/*
+ * Additionally, we allow to use `__restrict_arr' for declaring arrays as
+ * non-overlapping per C99.  That's supported since gcc 3.1, but it's not
+ * allowed in C++.
+ */
+#if defined(__cplusplus) || !__GNUC_PREREQ__(3, 1)
+#define __restrict_arr
+#elif defined __STDC_VERSION__ && __STDC_VERSION__ >= 199901L
+#define __restrict_arr       restrict
+#else
+#define __restrict_arr
+#endif
+
 /*
  * GNU C version 2.96 adds explicit branch prediction so that
  * the CPU back-end can hint the processor and also so that