From 3bfcb171026c4fd5c7caf807f79184a81c8af5b2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=B6rg=20Krause?= <joerg.krause@embedded.rocks>
Date: Sun, 11 Sep 2016 21:09:22 +0200
Subject: [PATCH] Check for std::future
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

std::future is not available for all architectures, e.g. it is missing
for ARMv5 (soft-float).

The problem is that libstdc++ only enables `std::future` if
`ATOMIC_INT_LOCK_FREE > 1` which is not true for the ARMv5 target.

As the future functionality is not used for much we just ifdef out the
parts from `std::future`.

Upstream-status: https://github.com/medoc92/libupnpp/issues/8

This patch is squashed from two upstream commits:
1/ d3e3cada667cca5b70693b351e5865231275dd82
2/ 90407dcc206987c8e58d61c64db539489f0717d2

Signed-off-by: Jörg Krause <joerg.krause@embedded.rocks>
---
 configure.ac         | 17 +++++++++++++++++
 libupnpp/config.h.in |  3 +++
 libupnpp/workqueue.h | 14 +++++++++++++-
 3 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/configure.ac b/configure.ac
index 877a773..9ff2058 100644
--- a/configure.ac
+++ b/configure.ac
@@ -47,6 +47,23 @@ AC_DEFINE([_FILE_OFFSET_BITS], [64], [File Offset size])
 AC_CHECK_LIB([rt], [clock_gettime], [], [])
 AC_CHECK_LIB([pthread], [pthread_create], [], [])
 
+# Check that std::future is available.
+AC_LANG_PUSH([C++])
+CXXFLAGS="-std=c++11 $CXXFLAGS"
+AC_MSG_CHECKING([whether std::future is available])
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <future>]],
+		[[std::future<int> f;]])],
+	[ AC_DEFINE([HAVE_STD_FUTURE], [1],
+		[Define to 1 if you have the `std::future`.])
+	  have_std_future=yes
+	],
+	[
+	  have_std_future=no
+	]
+)
+AC_MSG_RESULT([$have_std_future])
+AC_LANG_POP
+
 # The 2 following checks for libthreadutil and libixml are normally
 # unnecessary and even problematic. libupnpp does not use them directly,
 # and they should be used automatically because libupnpp is linked with them.
diff --git a/libupnpp/config.h.in b/libupnpp/config.h.in
index 39fa410..4471855 100644
--- a/libupnpp/config.h.in
+++ b/libupnpp/config.h.in
@@ -36,6 +36,9 @@
 /* Define to 1 if you have the <stdlib.h> header file. */
 #undef HAVE_STDLIB_H
 
+/* Define to 1 if you have the `std::future`. */
+#undef HAVE_STD_FUTURE
+
 /* Define to 1 if you have the <strings.h> header file. */
 #undef HAVE_STRINGS_H
 
diff --git a/libupnpp/workqueue.h b/libupnpp/workqueue.h
index 52a6138..9c0ec02 100644
--- a/libupnpp/workqueue.h
+++ b/libupnpp/workqueue.h
@@ -18,7 +18,9 @@
 #define _WORKQUEUE_H_INCLUDED_
 
 #include <thread>
+#if HAVE_STD_FUTURE
 #include <future>
+#endif
 #include <string>
 #include <queue>
 #include <list>
@@ -76,10 +78,14 @@ public:
     bool start(int nworkers, void *(workproc)(void *), void *arg) {
         std::unique_lock<std::mutex> lock(m_mutex);
         for (int i = 0; i < nworkers; i++) {
-            std::packaged_task<void *(void *)> task(workproc);
             Worker w;
+#if HAVE_STD_FUTURE
+            std::packaged_task<void *(void *)> task(workproc);
             w.res = task.get_future();
             w.thr = std::thread(std::move(task), arg);
+#else
+            w.thr = std::thread(workproc, arg);
+#endif
             m_worker_threads.push_back(std::move(w));
         }
         return true;
@@ -189,7 +195,11 @@ public:
         // Workers return (void*)1 if ok
         void *statusall = (void*)1;
         while (!m_worker_threads.empty()) {
+#if HAVE_STD_FUTURE
             void *status = m_worker_threads.front().res.get();
+#else
+            void *status = (void*) 1;
+#endif
             m_worker_threads.front().thr.join();
             if (status == (void *)0) {
                 statusall = status;
@@ -305,7 +315,9 @@ private:
 
     struct Worker {
         std::thread         thr;
+#if HAVE_STD_FUTURE
         std::future<void *> res;
+#endif
     };
     
     // Configuration
-- 
2.9.3