Re: Correct way to check for clock_gettime()

[Thomas Petazzoni]

Hello,

On Mon, 09 Aug 2010 11:50:19 -0600
Eric Blake <address@hidden> wrote:

> At any rate, I'd argue that glib's configure.ac (the one that does not
> check for -lrt) would be the best candidate for proposing an upstream
> patch.  glib in isolation will not use clock_gettime even if it is
> available through an alternate library; this is correct but not optimal
> behavior.  Therefore, it seems like it would be easier to get them to
> adopt the same approach as CTorrent of allowing -lrt to be able to use
> clock_gettime on more platforms.

Ok, in the end I came up with the following modification to glib's
configure.in :

========================================================================

Index: glib-2.24.1/configure.in
===================================================================
--- glib-2.24.1.orig/configure.in       2010-08-11 19:29:20.530916023 +0200
+++ glib-2.24.1/configure.in    2010-08-11 19:46:41.308866269 +0200
@@ -2392,13 +2392,14 @@
        LIBS="$glib_save_LIBS"
 fi
 
-AC_CHECK_FUNCS(clock_gettime, [], [
-  AC_CHECK_LIB(rt, clock_gettime, [
-    AC_DEFINE(HAVE_CLOCK_GETTIME, 1)
+AC_SEARCH_LIBS([clock_gettime], [rt], [
+    AC_DEFINE(HAVE_CLOCK_GETTIME, 1,[Have clock_gettime])
+])
+
+if test "$ac_cv_search_clock_gettime" = "-lrt"; then
     G_THREAD_LIBS="$G_THREAD_LIBS -lrt"
     G_THREAD_LIBS_FOR_GTHREAD="$G_THREAD_LIBS_FOR_GTHREAD -lrt"
-  ])
-])
+fi
 
 AC_CACHE_CHECK(for monotonic clocks,
     glib_cv_monotonic_clock,AC_COMPILE_IFELSE([AC_LANG_SOURCE([[

========================================================================

I'm not sure it's the perfect fix but it seems to work.

> Sure; although I can't guarantee that we can always provide a solution
> (let alone in a timely manner), it can't hurt to document your findings
> on the list for more eyes to look at.

Ok, thanks, will do.

Regards,

Thomas
-- 
Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com

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