configure: check whether std::atomic<T> works for function pointers

And ask the user to apply one of the patches we're carrying to their
Standard Libraries.

Change-Id: I7e6338336dd6468ead24ffff141139c79056922e
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

config.tests/common/atomicfptr/atomicfptr.cpp

@@ -0,0 +1,58 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 Intel Corporation.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the FOO module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL21$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file. Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** As a special exception, The Qt Company gives you certain additional
+** rights. These rights are described in The Qt Company LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include <atomic>
+
+typedef void (*fptr)(int);
+typedef std::atomic<fptr> atomicfptr;
+
+void testfunction(int) { }
+
+void test(volatile atomicfptr &a)
+{
+    fptr v = a.load(std::memory_order_acquire);
+    while (!a.compare_exchange_strong(v, &testfunction,
+                                      std::memory_order_acq_rel,
+                                      std::memory_order_acquire)) {
+        v = a.exchange(&testfunction);
+    }
+
+    a.store(&testfunction, std::memory_order_release);
+}
+
+int main(int, char **)
+{
+    atomicfptr fptr(testfunction);
+    test(fptr);
+    return 0;
+}

config.tests/common/atomicfptr/atomicfptr.pro

@@ -0,0 +1,3 @@
+SOURCES = atomicfptr.cpp
+CONFIG += c++11 console
+CONFIG -= qt app_bundle

config.tests/common/atomicfptr/icc2016_mac.diff

@@ -0,0 +1,18 @@
+Patch for fixing std::atomic support for function pointers for the Intel
+Composer XE 2016 (compiler version 16.0).
+
+To apply:
+  cd /opt/intel/compilers_and_libraries_2016/mac/include
+  sudo patch -p1 < /path-to-this-file/icc2016_mac.diff
+
+--- include/stdatomic.h.orig 2015-08-28 15:05:13.000000000 -0700
++++ include/stdatomic.h      2015-08-28 15:19:25.000000000 -0700
+@@ -451,7 +451,7 @@
+     }
+     _STRONG_INLINE atomic() _DEFAULTED
+     _STRONG_INLINE _CONSTEXPR atomic(T* _Ptr)
+-    : atomic_address(_Ptr)
++    : atomic_address((void*)_Ptr)
+     {
+     }
+     _STRONG_INLINE T* operator+=(ptrdiff_t _V) volatile

config.tests/common/atomicfptr/qnx66.txt

@@ -0,0 +1,3 @@
+Patch is available from QNX. Please see
+
+http://www.qnx.com/download/feature.html?programid=27555

configure

@@ -4486,6 +4486,14 @@ else
     CFG_ATOMIC64=no
 fi
 
+# Detect whether std::atomic works for function pointers -- some implementations are buggy
+if ! compileTest common/atomicfptr "std::atomic for function pointers"; then
+    echo "ERROR: detected a std::atomic implementation that fails for function pointers."
+    echo "Please apply the patch corresponding to your Standard Library vendor, found in"
+    echo "  $relpath/config.tests/common/atomicfptr"
+    exit 101
+fi
+
 # detect sse2 support
 CFG_SSE_LIST=
 if [ "${CFG_SSE2}" = "auto" ]; then

tools/configure/configureapp.cpp

@@ -2172,6 +2172,9 @@ bool Configure::checkAvailability(const QString &part)
     else if (part == "ATOMIC64-LIBATOMIC")
         available = tryCompileProject("common/atomic64", "LIBS+=-latomic");
 
+    else if (part == "ATOMICFPTR")
+        available = tryCompileProject("common/atomicfptr");
+
     else if (part == "ZLIB")
         available = findFile("zlib.h");
 
@@ -2338,6 +2341,15 @@ void Configure::autoDetection()
         dictionary["ATOMIC64"] = checkAvailability("ATOMIC64") ? "yes" :
                                  checkAvailability("ATOMIC64-LIBATOMIC") ? "libatomic" : "no";
 
+    // special case:
+    if (!checkAvailability("ATOMICFPTR")) {
+        dictionary["DONE"] = "error";
+        cout << "ERROR: detected an std::atomic implementation that fails for function pointers." << endl
+             << "Please apply the patch corresponding to your Standard Library vendor, found in" << endl
+             << sourcePath << "/config.tests/common/atomicfptr" << endl;
+        return;
+    }
+
     // Style detection
     if (dictionary["STYLE_WINDOWSXP"] == "auto")
         dictionary["STYLE_WINDOWSXP"] = checkAvailability("STYLE_WINDOWSXP") ? defaultTo("STYLE_WINDOWSXP") : "no";