From 47eb4e18d05e6b6362639a3a1454a5a354745f39 Mon Sep 17 00:00:00 2001
From: Pau Espin Pedrol <pespin@sysmocom.de>
Date: Fri, 1 May 2020 16:51:20 +0200
Subject: configure.ac: Fix HAVE_CLOCK_GETTIME undef when func in -lrt

AC_SEARCH_LIBS was finding the function correctly, but later on
AC_CHECK_FUNCS was not including the found LIBRARY_RT so the function
was not found, and hence HAVE_CLOCK_GETTIME ended up undefined (which in
turns disables support for osmo_clock_gettime() API).
This happened in systems like the soekris where the clock_gettime sybmol
is available in external lib -lrt.

Let's avoid double-checking for the function twice, and simply define
HAVE_CLOCK_GETTIME when AC_SEARCH_LIBS succeeds (the success action is
guaranteed to be called even if there's no extra lib required).

Change-Id: Iced1e0542cee6beb9f08f5299aad49fab142cfb4
---
 configure.ac | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/configure.ac b/configure.ac
index 352648b0..cba0a419 100644
--- a/configure.ac
+++ b/configure.ac
@@ -77,7 +77,9 @@ AC_SUBST(BACKTRACE_LIB)
 AX_PTHREAD
 
 # check for old glibc < 2.17 to get clock_gettime
-AC_SEARCH_LIBS([clock_gettime], [rt posix4], [LIBRARY_RT="$LIBS";LIBS=""])
+AC_SEARCH_LIBS([clock_gettime], [rt posix4],
+	       [AC_DEFINE(HAVE_CLOCK_GETTIME, 1, [Define if clock_gettime is available])
+	        LIBRARY_RT="$LIBS";LIBS="";])
 AC_SUBST(LIBRARY_RT)
 
 AC_ARG_ENABLE(doxygen,
@@ -103,7 +105,7 @@ AC_COMPILE_IFELSE([AC_LANG_SOURCE([char foo;])],
 CFLAGS="$saved_CFLAGS"
 AC_SUBST(SYMBOL_VISIBILITY)
 
-AC_CHECK_FUNCS(clock_gettime localtime_r)
+AC_CHECK_FUNCS(localtime_r)
 
 AC_DEFUN([CHECK_TM_INCLUDES_TM_GMTOFF], [
   AC_CACHE_CHECK(
-- 
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