tons of warnings about unused local typedefs with clang++

[Moritz Bunkus <moritz@…>]

When compiling anything using BOOST_RANGE_CONCEPT_ASSERT() clang++ emits tons of warnings about used local typedefs if compiled with -Wall.

This is a regression compared to 1.57.0.

Trivial example program:

#include <vector>
#include <boost/range/algorithm.hpp>

int
main(int, char**) {
  std::vector<int> v;
  boost::range::sort(v);
}

Compiled with:

clang++ -Wall -I$HOME/opt/boost/boost_1_58_0/include/ \
  -L$HOME/opt/boost/boost_1_58_0/lib/ -o cpp1 cpp1.cpp

Output (excerpt):

In file included from cpp1.cpp:46:
In file included from /home/mosu/opt/boost/boost_1_58_0/include/boost/range/algorithm.hpp:29:
In file included from /home/mosu/opt/boost/boost_1_58_0/include/boost/range/concepts.hpp:19:
/home/mosu/opt/boost/boost_1_58_0/include/boost/concept_check.hpp:51:7: warning: unused typedef 'boost_concept_check51' [-Wunused-local-typedef]
      BOOST_CONCEPT_ASSERT((Model));
…
…
313 warnings generated.

These are 313 warnings for that trivial example program above.

g++ 4.9.2 does not emit such warnings, with neither version.

clang++ 3.6.0 emits those warnings with Boost 1.58.0 but not with 1.57.0 or earlier.

[viboes]

You can use the corresponding -Wno-.... isn't it?

[viboes]

Duplicate #11239

[Moritz Bunkus <moritz@…>]

Of course I can find workarounds. I can use that option. Or drop -Wextra. Or not use clang++. Or chose to stay with Boost 1.57.0. None of that sounds like a solution. As I've pointed out prior versions of Boost didn't exhibit this behavior, and I actually like having warnings enabled for code that I write, and having a third-party library I use emit hundreds of warnings totally defeats that purpose. Encouraging application developers not to use warnings seems somewhat dangerous ground, too. Now if you tell me that there's technical reason why this typedef is really, really required and that the code wouldn't work otherwise then that would be something to consider. But until then I consider this a bug, and a regression.