Why I am getting clang-3.3 compile error with boost 1.53?

Solution Verified - Updated -

Environment

  • Red Hat Enterprise Linux 7.3
  • Red Hat Enterprise Linux 7.4

Issue

  • Compiling code like this fails with an error: no matching function for call to 'get' func(std::get<indices>(args)...): in RHEL7.4

    • Save the following code to test.cpp

      #include <boost/signals2/signal.hpp>
int main()
{
boost::signals2::signal<void()> s;
s();
}

    • Compile with:

      # clang test.cpp --std=c++11 -lstdc+ -o test

    • It will throw several errors, starting with:

      In file included from test.cpp:1:
In file included from /usr/include/boost/signals2/signal.hpp:38:
In file included from /usr/include/boost/signals2/variadic_signal.hpp:21:
/usr/include/boost/signals2/detail/variadic_slot_invoker.hpp:89:16: error: no matching function for call to 'get'
  func(std::get<indices>(args)...);
       ^-----------

Resolution

  • This is a known issue which is being tracked in Red Hat bugzilla : 1444258.
  • Fixing this issue is not in scope for RHEL 7.4 and will be reviewed again in the RHEL7.5 timeframe. For more details, please contact Red Hat Technical support

Workaround

  • Configure the Boost.Config header to be smarter about detecting C++11 features when compiling with Clang and libstdc++. Modify the code as follows:


    #include <boost/config.hpp>
#if defined(__clang__) && __cplusplus >= 201103L  
#  undef BOOST_NO_CXX11_HDR_TUPLE
#endif
#include <boost/signals2/signal.hpp>
int main()
{
boost::signals2::signal<void()> s;
 s();
}

Root Cause

  • Clang always identifies itself as GCC 4.2.1, which Boost 1.53 interprets to mean that no C++11 library features are supported. The <boost/config/stdlib/libstdcpp3.hpp> file has:

    //  C++0x headers in GCC 4.3.0 and later
// 
#if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 3) || !defined(__GXX_EXPERIMENTAL_CXX0X__)
#  define BOOST_NO_CXX11_HDR_ARRAY 
#  define BOOST_NO_CXX11_HDR_REGEX  
#  define BOOST_NO_CXX11_HDR_TUPLE
#  define BOOST_NO_CXX11_HDR_UNORDERED_MAP
#  define BOOST_NO_CXX11_HDR_UNORDERED_SET
#  define BOOST_NO_CXX11_HDR_FUNCTIONAL
#endif

  • In fact, clang is using the RHEL libstdc++ headers from GCC 4.8, which do support the <tuple> header. This mis-detection will happen for any version of Clang, because they all identify as GCC 4.2.1 so get treated the same by the logic above.

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