login_tty: Ensure declaration in <utmp.h>.

* tests/test-utmp-c++.cc: New file.
* modules/utmp-c++-tests: New file.

* tests/test-utmp.c: New file.
* modules/utmp-tests: New file.

* lib/login_tty.c: Include <utmp.h>.
* m4/login_tty.m4: New file.
(gl_FUNC_LOGIN_TTY): Moved here from m4/pty.m4. Set HAVE_LOGIN_TTY.
* m4/pty.m4 (gl_FUNC_LOGIN_TTY): Moved to m4/login_tty.m4.
* modules/login_tty (Files): Add m4/login_tty.m4.
(Depends-on): Add utmp. Remove pty. Update condition.
(configure.ac): Update condition. Invoke gl_UTMP_MODULE_INDICATOR
instead of gl_PTY_MODULE_INDICATOR.
(Include): List <utmp.h>.
* doc/glibc-functions/login_tty.texi: Mark the include file diversity as
fixed.
* tests/test-login_tty.c: Include <utmp.h>. Don't declare login_tty
here.

* lib/utmp.in.h: New file.
* m4/utmp_h.m4: New file.
* modules/utmp: New file.
* doc/glibc-headers/utmp.texi: New file.
* doc/gnulib.texi (Glibc Header File Substitutes): Include it.

3 files changed, 43 insertions, 7 deletions

diff --git a/doc/glibc-functions/login_tty.texi b/doc/glibc-functions/login_tty.texi
index b1adf8cd0b..3e743b1527 100644
--- a/doc/glibc-functions/login_tty.texi
+++ b/doc/glibc-functions/login_tty.texi
@@ -23,6 +23,13 @@ Portability problems fixed by Gnulib:
 This function is missing on some platforms:
 Minix 3.1.8, AIX 5.1, HP-UX 11, IRIX 6.5, Solaris 11.3, Android 5.1.
 @item
+This function is declared in @code{<utmp.h>} on glibc, Cygwin, Android,
+in @code{<util.h>} on macOS 11.1, NetBSD 5.0, OpenBSD 3.8,
+and in @code{<libutil.h>} on FreeBSD 13.0, Haiku.
+@c Also note that @code{<sys/types.h>} is
+@c a prerequisite of @code{<utmp.h>} on FreeBSD 8.0, OpenBSD 4.6 and
+@c of @code{<libutil.h>} on FreeBSD 8.0.
+@item
 This function requires linking with @code{-lutil} on some platforms:
 glibc 2.3.6, FreeBSD 13.0, NetBSD 5.0, OpenBSD 3.8.
 It is available without link options on other platforms:
@@ -34,11 +41,4 @@ Portability problems not fixed by Gnulib:
 @item
 This function is missing on some platforms:
 mingw, MSVC 14.
-@item
-This function is declared in @code{<utmp.h>} on glibc, Cygwin,
-in @code{<util.h>} on macOS 11.1, NetBSD 5.0, OpenBSD 3.8,
-and in @code{<libutil.h>} on FreeBSD 13.0, Haiku.
-Also note that @code{<sys/types.h>} is
-a prerequisite of @code{<utmp.h>} on FreeBSD 8.0, OpenBSD 4.6 and
-of @code{<libutil.h>} on FreeBSD 8.0.
 @end itemize
diff --git a/doc/glibc-headers/utmp.texi b/doc/glibc-headers/utmp.texi
new file mode 100644
index 0000000000..d7d1091e14
--- /dev/null
+++ b/doc/glibc-headers/utmp.texi
@@ -0,0 +1,34 @@
+@node utmp.h
+@section @file{utmp.h}
+
+Defines functions for login and logout (to a tty session) and for examining the
+history of logins and logouts.
+
+Documentation:
+@itemize
+@item
+@ifinfo
+@ref{Manipulating the Database,,Manipulating the User Accounting Database,libc},
+@end ifinfo
+@ifnotinfo
+@url{https://www.gnu.org/software/libc/manual/html_node/Manipulating-the-Database.html},
+@end ifnotinfo
+@item
+@uref{https://www.kernel.org/doc/man-pages/online/pages/man5/utmp.5.html,,man utmp}.
+@end itemize
+
+Gnulib module: utmp
+
+Portability problems fixed by Gnulib:
+@itemize
+@item
+This header file is missing on some platforms:
+FreeBSD 13.0, mingw, MSVC 14.
+@item
+@code{<sys/types.h>} is a prerequisite of @code{<utmp.h>} on some platforms:
+FreeBSD 8.0, OpenBSD 7.2.
+@end itemize
+
+Portability problems not fixed by Gnulib:
+@itemize
+@end itemize
diff --git a/doc/gnulib.texi b/doc/gnulib.texi
index 7388fb0b45..e9a4ace67f 100644
--- a/doc/gnulib.texi
+++ b/doc/gnulib.texi
@@ -3845,6 +3845,7 @@ not worked around by Gnulib.
 * sys/random.h::
 * sysexits.h::
 * ttyent.h::
+* utmp.h::
 @end menu
 
 @include glibc-headers/a.out.texi
@@ -3883,6 +3884,7 @@ not worked around by Gnulib.
 @include glibc-headers/sys_random.texi
 @include glibc-headers/sysexits.texi
 @include glibc-headers/ttyent.texi
+@include glibc-headers/utmp.texi
 
 @node Glibc Function Substitutes
 @chapter Glibc Function Substitutes