GCC's Warning in Boost Source

Question

I am using boost 1.63 and when I compile my application that includes #include <boost/algorithm/string.hpp>.

GCC complains:

In file included from /opt/boost/boost/mpl/aux_/na_assert.hpp:23,
                 from /opt/boost/boost/mpl/arg.hpp:25,
                 from /opt/boost/boost/mpl/placeholders.hpp:24,
                 from /opt/boost/boost/iterator/iterator_categories.hpp:17,
                 from /opt/boost/boost/iterator/iterator_facade.hpp:14,
                 from /opt/boost/boost/range/iterator_range_core.hpp:27,
                 from /opt/boost/boost/range/iterator_range.hpp:13,
                 from /opt/boost/boost/range/as_literal.hpp:22,
                 from /opt/boost/boost/algorithm/string/trim.hpp:19,
                 from /opt/boost/boost/algorithm/string.hpp:19,
         from [my source that includes <boost/algorithm/string.hpp>]
/opt/boost/boost/mpl/assert.hpp:188:21: warning: unnecessary parentheses in declaration of ‘assert_arg’ [-Wparentheses]
 failed ************ (Pred::************
                     ^
/opt/boost/boost/mpl/assert.hpp:193:21: warning: unnecessary parentheses in declaration of ‘assert_not_arg’ [-Wparentheses]
 failed ************ (boost::mpl::not_<Pred>::************
                     ^

I looked at the source and complained section is:

template< typename Pred >
failed ************ (Pred::************
      assert_arg( void (*)(Pred), typename assert_arg_pred<Pred>::type )
    );

template< typename Pred >
failed ************ (boost::mpl::not_<Pred>::************
      assert_not_arg( void (*)(Pred), typename assert_arg_pred_not<Pred>::type )
    );

Questions:

• what is failed ************ (Pred::************? The syntax looks weird to me.
• how I can fix it without suppressing all similar warnings? As GCC's warnings are usually valid and helpful in detecting issues.

I searched online, and the closest, related one is this. But its solution seems to just suppress the warnings.

Thanks!

Answer 1

Normally GCC and Clang automatically suppress warnings from headers in /usr. However, it seems that for /opt it doesn't. To tell the compiler that the boost headers should be treated as system headers, use -isystem instead of -I to add the boost headers to the include paths.