Re: boot-time: straighten code

[Bruno Haible <bruno@clisp.org>]

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: In function 'get_boot_time_uncached':
> boot-time.c:111:26: error: 'BOOT_TIME' undeclared (first use in this function)
>        if (ut->ut_type == BOOT_TIME)
>                           ^

Unlike USER_PROCESS, which is defined in all versions of Android's <utmp.h>,
BOOT_TIME is only defined in newer versions.

When compiling against an older version, we need to use the value from the
newer versions — otherwise a binary built against an older version might
not work right when running on a newer Android.

This patch does 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.h (BOOT_TIME): Add fallback.

diff --git a/lib/readutmp.h b/lib/readutmp.h
index 1cf588d265..f7cad36d44 100644
--- a/lib/readutmp.h
+++ b/lib/readutmp.h
@@ -249,6 +249,13 @@ struct utmpx32
 # define WTMP_FILE "/etc/wtmp"
 #endif
 
+/* In early versions of Android, <utmp.h> did not define BOOT_TIME, only
+   USER_PROCESS.  We need to use the value that is defined in newer versions
+   of Android.  */
+#if defined __ANDROID__ && !defined BOOT_TIME
+# define BOOT_TIME 2
+#endif
+
 /* Some platforms, such as OpenBSD, don't have an ut_type field and don't have
    the BOOT_TIME and USER_PROCESS macros.  But we want to support them in
    'struct gl_utmp'.  */