epicsMutexPriorityInversionTest.c: check __GLIBC_PREREQ(2,4) when compiling

(non-portable) CPU-affinity extensions only available in glibc 2.4 and
  higher.

src/libCom/test/epicsMutexPriorityInversionTest.c

@@ -1,6 +1,8 @@
 #ifndef _GNU_SOURCE
 #define _GNU_SOURCE
 #endif
+
+#include <features.h>
 #include <sched.h>
 #include <epicsThread.h>
 #include <epicsEvent.h>
@@ -16,6 +18,12 @@
 
 #define  SPIN_SECS 3000000
 
+#if defined(__GLIBC__) && defined(__GLIBC_PREREQ) && __GLIBC_PREREQ(2,4)
+#define HAVE_CPU_AFFINITY
+#else
+#undef  HAVE_CPU_AFFINITY
+#endif
+
 typedef struct ThreadArg_ {
 	epicsEventId           sync;
 	epicsEventId           done;
@@ -39,11 +47,13 @@ struct timespec now;
  */
 static void setThreadAffinity(int cpu)
 {
+#ifdef HAVE_CPU_AFFINITY
 cpu_set_t cset;
 
 	CPU_ZERO( &cset );
 	CPU_SET( cpu, &cset );
 	testOk1 ( 0 == pthread_setaffinity_np( pthread_self(), sizeof(cset), &cset ) );
+#endif
 }
 
 /*
@@ -51,6 +61,7 @@ cpu_set_t cset;
  */
 static void checkAffinity(int cpu)
 {
+#ifdef HAVE_CPU_AFFINITY
 cpu_set_t cset;
 
 	if ( pthread_getaffinity_np( pthread_self(), sizeof(cset), &cset) ) {
@@ -58,6 +69,7 @@ cpu_set_t cset;
 		return;
 	}
 	testOk ( 1 == CPU_COUNT( &cset ) && CPU_ISSET( cpu, &cset ), "Checking CPU affinity mask" );
+#endif
 }
 
 
@@ -212,6 +224,12 @@ struct    sched_param p_pri;
 
 	testPlan(NUM_TESTS);
 
+#ifndef HAVE_CPU_AFFINITY
+#warning "glibc too old for this test: pthread_setaffinity_np() not available..."
+	testSkip( NUM_TESTS, "glibc too old for this test: pthread_setaffinity_np() not implemented!" );
+	return testDone();
+#endif
+
 	p_pri.sched_priority = sched_get_priority_min( SCHED_FIFO );
 	if ( sched_setscheduler( 0, SCHED_FIFO, &p_pri ) ) {
 		testDiag("SCHED_FIFO not engaged - maybe you need to be root to run this test?");