Linux: consolidate dup2 implementation

Use dup2 syscall if defined, otherwise use dup3.

Checked on x86_64-linux-gnu.
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
Tested-by: Carlos O'Donell <carlos@redhat.com>

1 files changed, 40 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/dup2.c b/sysdeps/unix/sysv/linux/dup2.c
new file mode 100644
index 0000000000..1182780e15
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/dup2.c
@@ -0,0 +1,40 @@
+/* Duplicate a file descriptor.  Linux version.
+   Copyright (C) 2011-2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library.  If not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <fcntl.h>
+#include <unistd.h>
+#include <sysdep.h>
+
+/* Duplicate FD to FD2, closing the old FD2 and making FD2 be
+   open the same file as FD is.  Return FD2 or -1.  */
+int
+__dup2 (int fd, int fd2)
+{
+#ifdef __NR_dup2
+  return INLINE_SYSCALL_CALL (dup2, fd, fd2);
+#else
+  /* For the degenerate case, check if the fd is valid (by trying to
+     get the file status flags) and return it, or else return EBADF.  */
+  if (fd == fd2)
+    return __libc_fcntl (fd, F_GETFL, 0) < 0 ? -1 : fd;
+
+  return INLINE_SYSCALL_CALL (dup3, fd, fd2, 0);
+#endif
+}
+libc_hidden_def (__dup2)
+weak_alias (__dup2, dup2)