[Boost-bugs] [Boost C++ Libraries] #11876: Boost.Graph conflicts with Qt's foreach macro

Subject: [Boost-bugs] [Boost C++ Libraries] #11876: Boost.Graph conflicts with Qt's foreach macro
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2015-12-28 14:56:52

#11876: Boost.Graph conflicts with Qt's foreach macro
----------------------+------------------------------
 Reporter:  richel@…  |       Type:  Bugs
   Status:  new       |  Milestone:  To Be Determined
Component:  None      |    Version:  Boost 1.54.0
 Severity:  Problem   |   Keywords:  Graph BGL Qt
----------------------+------------------------------
 This is a similar problem as https://svn.boost.org/trac/boost/ticket/6455,

 where the Qt `foreach` macro conflicts with the `boost::foreach::tag` in
 file `/usr/include/boost/foreach.hpp`.

 This is a simple Qt example that reproduces the error (also supplied as an
 attachment):

 {{{
 #include <boost/graph/adjacency_list.hpp>
 #include <QCoreApplication>
 #include <fstream>
 #include <boost/graph/adjacency_list.hpp>
 #include <boost/graph/graphviz.hpp>

 int main(int argc, char *argv[])
 {
   QCoreApplication a(argc, argv);

   std::ofstream f("filename.dot");
   boost::write_graphviz(
     f,
     boost::adjacency_list<>()
   );
   return a.exec();
 }
 }}}

 For the following Qt Creator project file:

 {{{
 QT       += core
 QT       -= gui
 CONFIG   += console
 CONFIG   -= app_bundle
 TEMPLATE = app
 SOURCES += main.cpp
 }}}

 The error given is:

 {{{
 In file included from /usr/include/boost/graph/graphviz.hpp:35:0,
                  from ../CppBoostGraphAndQtConflictQtConsole/main.cpp:5:
 /usr/include/boost/foreach.hpp:169:42: error: 'boost::Q_FOREACH::tag' has
 not been declared
  boost_foreach_is_lightweight_proxy(T *&, BOOST_FOREACH_TAG_DEFAULT) {
 return 0; }
 }}}

 The error does not occur if 'boost/graph/adjacency_list.hpp' is #included
 either before `QCoreApplication` or after. This is a workaround.

 I cannot see if this error is still present in later versions of Boost. If
 it is still present, I hope I have contributed in letting Boost.Graph and
 Qt work together seamlessly.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/11876>
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