Re: boot-time: straighten code

[Bruno Haible]

Po Lu wrote:
> During the automated build of the Android port, the following errors
> were encountered with the Android NDK r10b and __ANDROID_API__ set to 8
> (which is the oldest configuration Emacs supports.)
> ...
> boot-time.c:111:26: note: each undeclared identifier is reported only once 
> for each function it appears in
> boot-time.c:126:3: error: implicit declaration of function 'endutent' 
> [-Werror=implicit-function-declaration]
>    END_UTMP_ENT ();
>    ^

endutent() exists in Android, already in API 8. It's just that its declaration
is missing from <utmp.h> until ca. 2015.

Should be fixed through this patch. Also, it removes a declaration that was
needed only for Ultrix 4.3. Gnulib dropped Ultrix support in 2018.

Paul Eggert wrote:
> As I understand it, the utmp/utmpx functions 
> are a losing cause on Android since they never return anything. If so, 
> it's simpler to bypass these functions on that platform.

It's more future-proof to continue to use the API that they have. Who knows,
they might add useful data into the UTMP_FILE at some point. (E.g. they had a
broken localeconv() function for a long time; then they actually fixed it.)


2023-08-13  Bruno Haible  <bruno@clisp.org>

        readutmp, boot-time: Fix compilation error on old Android.
        Reported by Po Lu in
        <https://lists.gnu.org/archive/html/bug-gnulib/2023-08/msg00108.html>.
        * lib/readutmp.c (endutent): New fallback declaration, for Android.
        (getutent): Remove Ultrix workaround from 2000-04-05.
        * lib/boot-time.c: Likewise.
        * m4/readutmp.m4 (gl_PREREQ_READUTMP_H): Test whether endutent is
        declared, not getutent.
        * doc/glibc-functions/endutent.texi: Mention the Android bug.

diff --git a/doc/glibc-functions/endutent.texi 
b/doc/glibc-functions/endutent.texi
index 5e12e23c44..b4f3dd397a 100644
--- a/doc/glibc-functions/endutent.texi
+++ b/doc/glibc-functions/endutent.texi
@@ -28,4 +28,7 @@
 @item
 This function is missing on some platforms:
 macOS 11.1, FreeBSD 13.0, OpenBSD 6.7, Minix 3.1.8, mingw, MSVC 14.
+@item
+This function is not declared on some platforms:
+Android before ca.@: 2015.
 @end itemize
diff --git a/lib/boot-time.c b/lib/boot-time.c
index d813bfa582..c359954f19 100644
--- a/lib/boot-time.c
+++ b/lib/boot-time.c
@@ -65,8 +65,10 @@
 # define UT_USER(UT) ((UT)->ut_user)
 #endif
 
-#if !HAVE_UTMPX_H && HAVE_UTMP_H && defined UTMP_NAME_FUNCTION && 
!HAVE_DECL_GETUTENT
-struct utmp *getutent (void);
+#if !HAVE_UTMPX_H && HAVE_UTMP_H && defined UTMP_NAME_FUNCTION
+# if !HAVE_DECL_ENDUTENT /* Android */
+void endutent (void);
+# endif
 #endif
 
 #if defined __linux__ || HAVE_UTMPX_H || HAVE_UTMP_H || defined __CYGWIN__ || 
defined _WIN32
diff --git a/lib/readutmp.c b/lib/readutmp.c
index ef9f0aff43..0b7732b165 100644
--- a/lib/readutmp.c
+++ b/lib/readutmp.c
@@ -314,9 +314,11 @@ have_boot_time (struct utmp_alloc a)
   return false;
 }
 
-# if !HAVE_UTMPX_H && HAVE_UTMP_H && defined UTMP_NAME_FUNCTION && 
!HAVE_DECL_GETUTENT
-struct utmp *getutent (void);
+#if !HAVE_UTMPX_H && HAVE_UTMP_H && defined UTMP_NAME_FUNCTION
+# if !HAVE_DECL_ENDUTENT /* Android */
+void endutent (void);
 # endif
+#endif
 
 static int
 read_utmp_from_file (char const *file, idx_t *n_entries, STRUCT_UTMP 
**utmp_buf,
diff --git a/m4/readutmp.m4 b/m4/readutmp.m4
index fff8d4eb7b..9dffe981b8 100644
--- a/m4/readutmp.m4
+++ b/m4/readutmp.m4
@@ -1,4 +1,4 @@
-# readutmp.m4 serial 28
+# readutmp.m4 serial 29
 dnl Copyright (C) 2002-2023 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -55,7 +55,7 @@ AC_DEFUN_ONCE([gl_PREREQ_READUTMP_H]
   if test $ac_cv_header_utmp_h = yes || test $ac_cv_header_utmpx_h = yes; then
     dnl Prerequisites of lib/readutmp.h and lib/readutmp.c.
     AC_CHECK_FUNCS_ONCE([utmpname utmpxname])
-    AC_CHECK_DECLS([getutent],,,[[
+    AC_CHECK_DECLS([endutent],,,[[
 /* <sys/types.h> is a prerequisite of <utmp.h> on FreeBSD 8.0, OpenBSD 4.6.  */
 #include <sys/types.h>
 #ifdef HAVE_UTMP_H