Build issue with HPX_WITH_NETWORKING=OFF

[Gregor Daiß]

The current HPX master branch ( 1cbb0d6 ) does not compile when HPX_WITH_NETWORKING is set to OFF (using clang 12, single node CUDA build). This appears to be a new issue, as the same build without networking works using HPX 1.9.0.

Setting HPX_WITH_NETWORKING=ON fixes the compilation on master as well, with OFF I get the following compilation errors:

        io_pool_->run(false);
                ^
src/hpx/libs/core/io_service/include/hpx/io_service/io_service_pool_fwd.hpp:13:27: note: forward declaration of 'hpx::util::io_service_pool'
    class HPX_CORE_EXPORT io_service_pool;
                          ^
src/hpx/libs/full/runtime_distributed/src/runtime_distributed.cpp:555:19: error: member access into incomplete type 'hpx::util::io_service_pool'
        main_pool_->stop();
                  ^
src/hpx/libs/core/io_service/include/hpx/io_service/io_service_pool_fwd.hpp:13:27: note: forward declaration of 'hpx::util::io_service_pool'
    class HPX_CORE_EXPORT io_service_pool;
                          ^
src/hpx/libs/full/runtime_distributed/src/runtime_distributed.cpp:579:19: error: member access into incomplete type 'hpx::util::io_service_pool'
        main_pool_->thread_run(0);
                  ^
src/hpx/libs/core/io_service/include/hpx/io_service/io_service_pool_fwd.hpp:13:27: note: forward declaration of 'hpx::util::io_service_pool'
    class HPX_CORE_EXPORT io_service_pool;
                          ^
src/hpx/libs/full/runtime_distributed/src/runtime_distributed.cpp:643:20: error: member access into incomplete type 'hpx::util::io_service_pool'
        timer_pool_->stop();
                   ^
src/hpx/libs/core/io_service/include/hpx/io_service/io_service_pool_fwd.hpp:13:27: note: forward declaration of 'hpx::util::io_service_pool'
    class HPX_CORE_EXPORT io_service_pool;
                          ^
src/hpx/libs/full/runtime_distributed/src/runtime_distributed.cpp:646:24: error: member access into incomplete type 'hpx::util::io_service_pool'
            timer_pool_->join();
                       ^
src/hpx/libs/core/io_service/include/hpx/io_service/io_service_pool_fwd.hpp:13:27: note: forward declaration of 'hpx::util::io_service_pool'
    class HPX_CORE_EXPORT io_service_pool;
                          ^
src/hpx/libs/full/runtime_distributed/src/runtime_distributed.cpp:647:24: error: member access into incomplete type 'hpx::util::io_service_pool'
            timer_pool_->clear();
                       ^
src/hpx/libs/core/io_service/include/hpx/io_service/io_service_pool_fwd.hpp:13:27: note: forward declaration of 'hpx::util::io_service_pool'
    class HPX_CORE_EXPORT io_service_pool;
                          ^
src/hpx/libs/full/runtime_distributed/src/runtime_distributed.cpp:652:17: error: member access into incomplete type 'hpx::util::io_service_pool'
        io_pool_->stop();
                ^
src/hpx/libs/core/io_service/include/hpx/io_service/io_service_pool_fwd.hpp:13:27: note: forward declaration of 'hpx::util::io_service_pool'
    class HPX_CORE_EXPORT io_service_pool;
                          ^
src/hpx/libs/full/runtime_distributed/src/runtime_distributed.cpp:655:21: error: member access into incomplete type 'hpx::util::io_service_pool'
            io_pool_->join();
                    ^
src/hpx/libs/core/io_service/include/hpx/io_service/io_service_pool_fwd.hpp:13:27: note: forward declaration of 'hpx::util::io_service_pool'
    class HPX_CORE_EXPORT io_service_pool;
                          ^
src/hpx/libs/full/runtime_distributed/src/runtime_distributed.cpp:656:21: error: member access into incomplete type 'hpx::util::io_service_pool'
            io_pool_->clear();
                    ^
src/hpx/libs/core/io_service/include/hpx/io_service/io_service_pool_fwd.hpp:13:27: note: forward declaration of 'hpx::util::io_service_pool'
    class HPX_CORE_EXPORT io_service_pool;
                          ^
9 errors generated.