BOOST_STATIC_ASSERT raises unused typedef error with new Apple Xcode 7

[Francis Dupont <fdupont@…>]

I've just updated by Apple Xcode (OS X compiler suite) to version 7. g++ version returns:

Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr --with-gxx-include-dir=/usr/include/c++/4.2.1
Apple LLVM version 7.0.0 (clang-700.0.72)
Target: x86_64-apple-darwin14.5.0
Thread model: posix

Boost version is 1.58.0 and is installed by brew. The last stable version 1.59.0 has exactly the same code so should share the issue.

Code using BOOST_STATIC_ASSERT raises this kind of errors:

In file included from encode/base_n.cc:16:
../../../src/lib/util/encode/binary_from_base32hex.h:46:9: error: unused typedef 'boost_static_assert_typedef_46' [-Werror,-Wunused-local-typedef]
        BOOST_STATIC_ASSERT(0x80 == sizeof(lookup_table));
        ^
/usr/local/include/boost/static_assert.hpp:170:16: note: expanded from macro 'BOOST_STATIC_ASSERT'
               BOOST_JOIN(boost_static_assert_typedef_, __LINE__) BOOST_STATIC_ASSERT_UNUSED_ATTRIBUTE
               ^
/usr/local/include/boost/config/suffix.hpp:544:28: note: expanded from macro 'BOOST_JOIN'
#define BOOST_JOIN( X, Y ) BOOST_DO_JOIN( X, Y )
                           ^
/usr/local/include/boost/config/suffix.hpp:545:31: note: expanded from macro 'BOOST_DO_JOIN'
#define BOOST_DO_JOIN( X, Y ) BOOST_DO_JOIN2(X,Y)
                              ^
/usr/local/include/boost/config/suffix.hpp:546:32: note: expanded from macro 'BOOST_DO_JOIN2'
#define BOOST_DO_JOIN2( X, Y ) X##Y
                               ^
<scratch space>:77:1: note: expanded from here
boost_static_assert_typedef_46
^

Note it is not a new issue, cf #7242. But the fix in static_assert.hpp:

//
// If the compiler warns about unused typedefs then enable this:
//
#if defined(__GNUC__) && ((__GNUC__ > 4) || ((__GNUC__ == 4) && (__GNUC_MINOR__ 
>= 7)))
#  define BOOST_STATIC_ASSERT_UNUSED_ATTRIBUTE __attribute__((unused))
#else
#  define BOOST_STATIC_ASSERT_UNUSED_ATTRIBUTE
#endif

requires to handle the new Apple Clang. I tried with success:

#if defined(__GNUC__) && ((__GNUC__ > 4) || ((__GNUC__ == 4) && (__GNUC_MINOR__ >= 7))) || (defined(__apple_build_version__) && (__apple_build_version__ >= 7000000))

I am attaching the diff.

[Francis Dupont <fdupont@…>]

static_assert.hpp diff

[Michel Morin]

This is already fixed in 'develop' branch: ​https://github.com/boostorg/static_assert/tree/develop