m4: fix gl_TIMER_TIME() detection of threads on uClibc The timer_time.m4 gl_TIMER_TIME function determines which libraries need to be linked to get access to the timer function, generally -lrt for Linux systems. On platforms where threads are used, librt typically uses thread functions from libpthread. However, the test to determine whether the platform has thread or not is incorrect: it assumes that if the C library is uClibc, then threads are not available. This is actually not true: uClibc has configurable thread support, and when thread support is available, librt calls libpthread functions. This is important when static linking is used, because otherwise only -lrt is used at link time, which fails because librt calls undefined thread functions. Both -lrt and -lpthread must be passed. This problem is fixed by making the uClibc thread detection a bit smarter, thanks to the usage of the __HAS_NO_THREADS__ macro defined in <bits/uClibc_config.h>, which itself is included by <features.h>. Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com> Signed-off-by: Eric Blake <eblake@redhat.com>

--- a/ChangeLog	Fri Feb 21 13:02:10 2014 -0700
+++ b/ChangeLog	Sat Feb 22 00:41:38 2014 +0100
@@ -1,3 +1,8 @@
+2014-02-21  Thomas Petazzoni  <thomas.petazzoni@free-electrons.com>  (tiny change)
+	timer: fix uClibc detection of threading
+	* m4/time_time.m4 (gl_TIMER_TIME): Detect whether threads are
+	enabled in uClibc.
+
 2014-02-21  Eric Blake  <eblake@redhat.com>
 
 	maintainer-makefiles: provide AC_PROG_SED for older autoconf

--- a/m4/timer_time.m4	Fri Feb 21 13:02:10 2014 -0700
+++ b/m4/timer_time.m4	Sat Feb 22 00:41:38 2014 +0100
@@ -28,7 +28,7 @@
 #include <features.h>
 #ifdef __GNU_LIBRARY__
  #if ((__GLIBC__ == 2 && __GLIBC_MINOR__ >= 2) || (__GLIBC__ > 2)) \
-     && !defined __UCLIBC__
+     && !(__UCLIBC__ && __HAS_NO_THREADS__)
   Thread emulation available
  #endif
 #endif