Add autoconf test for stdatomic

Also do conditional compilation for stdatomic and pthread.

configure.ac

@@ -91,6 +91,9 @@ CC="$PTHREAD_CC"
 CXX="$PTHREAD_CXX"
 ])
 
+# Atomics
+AC_CHECK_HEADERS([stdatomic.h])
+
 # Check for poll.h (it's in POSIX so everyone should have it?)
 AC_CHECK_HEADERS([poll.h])
 

src/iperf.h

@@ -1,5 +1,5 @@
 /*
- * iperf, Copyright (c) 2014-2020, The Regents of the University of
+ * iperf, Copyright (c) 2014-2020, 2023, The Regents of the University of
  * California, through Lawrence Berkeley National Laboratory (subject
  * to receipt of any required approvals from the U.S. Dept. of
  * Energy).  All rights reserved.
@@ -73,8 +73,13 @@
 #include <openssl/evp.h>
 #endif // HAVE_SSL
 
+#ifdef HAVE_PTHREAD
 #include <pthread.h>
+#endif // HAVE_PTHREAD
+
+#ifdef HAVE_STDATOMIC_H
 #include <stdatomic.h>
+#endif // HAVE_STDATOMIC_H
 
 #if !defined(__IPERF_API_H)
 //typedef uint64_t iperf_size_t;

src/iperf_api.h

@@ -1,5 +1,5 @@
 /*
- * iperf, Copyright (c) 2014-2022, The Regents of the University of
+ * iperf, Copyright (c) 2014-2023, The Regents of the University of
  * California, through Lawrence Berkeley National Laboratory (subject
  * to receipt of any required approvals from the U.S. Dept. of
  * Energy).  All rights reserved.
@@ -38,7 +38,9 @@
 extern "C" { /* open extern "C" */
 #endif
 
+#ifdef HAVE_STDATOMIC_H
 #include <stdatomic.h>
+#endif // HAVE_STDATOMIC_H
 
 struct iperf_test;
 struct iperf_stream_result;