[2/2] posix: Deprecate group_member for Linux

diff --git a/posix/Makefile b/posix/Makefile
index b46ff3259c..09308d4568 100644
--- a/posix/Makefile
+++ b/posix/Makefile
@@ -295,6 +295,7 @@  tests := \
   tst-gnuglob \
   tst-gnuglob64 \
   tst-group_member2 \
+  tst-group_member \
   tst-mmap \
   tst-mmap-offset \
   tst-nanosleep \
@@ -616,6 +617,8 @@  bug-glob1-ARGS = "$(objpfx)"
 tst-execvp3-ARGS = --test-dir=$(objpfx)
 CFLAGS-tst-spawn3.c += -DOBJPFX=\"$(objpfx)\"
 
+CFLAGS-tst-group_member.c += -Wno-error=deprecated-declarations
+
 # Test voluntarily overflows struct dirent
 CFLAGS-bug-glob2.c += $(no-fortify-source)
 
diff --git a/posix/group_member.h b/posix/group_member.h
new file mode 100644
index 0000000000..cc3c3ba603
--- /dev/null
+++ b/posix/group_member.h
@@ -0,0 +1,29 @@ 
+/* Copyright (C) 2023 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/>.  */
+
+#ifndef _GROUP_MEMBER_H
+#define _GROUP_MEMBER_H 1
+
+#ifdef	__USE_GNU
+/* Return nonzero iff the calling process is in group GID.  */
+extern int group_member (__gid_t __gid) __THROW;
+/* Return nonzero iff the calling process is in group GID.  Return
+   -1 on error and set errno.  */
+extern int group_member2 (__gid_t __gid) __THROW;
+#endif
+
+#endif /* GROUP_MEMBER_H */
diff --git a/posix/tst-group_member.c b/posix/tst-group_member.c
new file mode 100644
index 0000000000..7f70841832
--- /dev/null
+++ b/posix/tst-group_member.c
@@ -0,0 +1,41 @@ 
+/* Basic tests for group_member.
+   Copyright (C) 2023 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 <alloca.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <support/check.h>
+
+static int do_test (void)
+{
+  int n;
+  gid_t *groups;
+
+  n = getgroups (0, NULL);
+  groups = alloca (n * sizeof (*groups));
+  n = getgroups (n, groups);
+
+  while (n-- > 0)
+    TEST_COMPARE (1, group_member(groups[n]));
+
+  return EXIT_SUCCESS;
+}
+
+#include <support/test-driver.c>
diff --git a/posix/unistd.h b/posix/unistd.h
index 96816b186d..d73a9eeea2 100644
--- a/posix/unistd.h
+++ b/posix/unistd.h
@@ -710,13 +710,10 @@  extern __gid_t getegid (void) __THROW;
    of its supplementary groups in LIST and return the number written.  */
 extern int getgroups (int __size, __gid_t __list[]) __THROW __wur
     __fortified_attr_access (__write_only__, 2, 1);
+
 #ifdef	__USE_GNU
-/* Return nonzero iff the calling process is in group GID.  */
-extern int group_member (__gid_t __gid) __THROW;
-/* Return nonzero iff the calling process is in group GID.  Return
-   -1 on error and set errno.  */
-extern int group_member2 (__gid_t __gid) __THROW;
-#endif
+# include <group_member.h>
+#endif 
 
 /* Set the user ID of the calling process to UID.
    If the calling process is the super-user, set the real
diff --git a/sysdeps/unix/sysv/linux/group_member.h b/sysdeps/unix/sysv/linux/group_member.h
new file mode 100644
index 0000000000..97a9f30dfe
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/group_member.h
@@ -0,0 +1,27 @@ 
+/* Copyright (C) 2023 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/>.  */
+
+#ifndef _GROUP_MEMBER_H
+#define _GROUP_MEMBER_H 1
+
+#ifdef	__USE_GNU
+/* Return nonzero iff the calling process is in group GID.  Deprecated */
+extern int group_member (__gid_t __gid) __THROW
+	__attribute_deprecated_msg__ ("may overflow the stack");
+#endif
+
+#endif /* GROUP_MEMBER_H */