[PATCH v2] close_range.2: Add _GNU_SOURCE and unistd.h to SYNOPSIS

[Mark Wielaard <mark@klomp.org>]

close_range is defined in unistd.h when _GNU_SOURCE is defined.
The linux/close_range.h include file only defines the (linux specific)
flags constants. The flags argument is an int, not an unsigned int, in
the glibc wrapper. Use the close_range library call in the example code
instead of syscall.

Fixes: 71a62d6c3c56 ("close_range.2: Glibc added a wrapper recently")
Fixes: c2356ba085ed ("close_range.2: Glibc 2.34 has added a close_range() wrapper")

Reported-by: Alexandra Hájková <ahajkova@redhat.com>
Signed-off-by: Mark Wielaard <mark@klomp.org>
---
 man2/close_range.2 | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/man2/close_range.2 b/man2/close_range.2
index 380a47365..62b728e96 100644
--- a/man2/close_range.2
+++ b/man2/close_range.2
@@ -11,10 +11,13 @@ Standard C library
 .RI ( libc ", " \-lc )
 .SH SYNOPSIS
 .nf
-.B #include <linux/close_range.h>
+.BR "#define _GNU_SOURCE" "         /* See feature_test_macros(7) */"
+.B #include <unistd.h>
+.P
+.BR "#include <linux/close_range.h>" "  /* For the flags constants */"
 .P
 .BI "int close_range(unsigned int " first ", unsigned int " last ,
-.BI "                unsigned int " flags );
+.BI "                int " flags );
 .fi
 .SH DESCRIPTION
 The
@@ -205,7 +208,6 @@ result from the calls to
 #include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
-#include <sys/syscall.h>
 #include <unistd.h>
 \&
 /* Show the contents of the symbolic links in /proc/self/fd */
@@ -259,7 +261,7 @@ main(int argc, char *argv[])
 \&
     printf("========= About to call close_range() =======\en");
 \&
-    if (syscall(SYS_close_range, 3, \[ti]0U, 0) == \-1) {
+    if (close_range(3, \[ti]0U, 0) == \-1) {
         perror("close_range");
         exit(EXIT_FAILURE);
     }
-- 
2.39.3