Lock used in flyweight causes erroneous "unused variable" warning when compiling with clang

[Pierre Imai <pierre.imai@…>]

The lock functionality in boost/flyweight/detail/flyweight_core.hpp causes the following warning when compiled with "Apple clang version 4.0 (tags/Apple/clang-421.0.60) (based on LLVM 3.1svn)" with option "-Wunused-variable":

In file included from /opt/local/include/boost/flyweight/flyweight.hpp:22:
/opt/local/include/boost/flyweight/detail/flyweight_core.hpp:189:22: error: unused variable 'lock' [-Werror,-Wunused-variable]
    lock_type        lock(mutex());

This problem can be fixed by adding the following code to the file, before / after the corresponding blocks for MSVC

#ifdef __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunused-variable"
#endif

#ifdef __clang__
#pragma clang diagnostic pop
#endif

[Joaquín M López Muñoz]

Hi Pierre,

Can you provide me with two bits of additional info?

• Can you check the values of clang_major and clang_minor? I'd like make the patch using BOOST_WORKAROUND and BOOST_TESTED_AT so as to record the specific version of Clang where this is happening.
• Do you have access to GCC in your environment? Does the equivalent warning happen?

Thank you,

[Joaquín M López Muñoz]

Can't fix due to lack of feedback from reporter.