Compiler warning: objects of type `fc::optional` may be used uninitialized

[abitmore]

Build Error Description

Also reported in https://github.com/bitshares/bitshares-core/issues/2348.

/bitshares-core/libraries/protocol/fee_schedule_calc.cpp: In member function ‘graphene::protocol::calc_fee_visitor::result_type graphene::protocol::calc_fee_visitor::operator()(const OpType&) const [with OpType = graphene::protocol::asset_create_operation; graphene::protocol::calc_fee_visitor::result_type = long unsigned int]’:
/bitshares-core/libraries/protocol/fee_schedule_calc.cpp:70:26: warning: ‘sub_asset_creation_fee’ may be used uninitialized in this function [-Wmaybe-uninitialized]
       optional<uint64_t> sub_asset_creation_fee;
                          ^

In file included from /bitshares-core/tests/tests/operation_tests.cpp:43:0:
/bitshares-core/tests/tests/../common/database_fixture.hpp: In member function ‘void operation_tests::update_uia::test_method()’:
/bitshares-core/tests/tests/../common/database_fixture.hpp:148:9: warning: ‘bak.fc::optional<graphene::db::object_id<1, 2> >::_value[0]’ may be used uninitialized in this function [-Wmaybe-uninitialized]
    auto bak = op.field; \
         ^~~
/bitshares-core/tests/tests/../common/database_fixture.hpp:148:9: note: ‘bak.fc::optional<graphene::db::object_id<1, 2> >::_value[0]’ was declared here
    auto bak = op.field; \
         ^
/bitshares-core/tests/tests/../common/database_fixture.hpp:148:9: note: in definition of macro ‘REQUIRE_THROW_WITH_VALUE_2’
    auto bak = op.field; \
         ^~~
/bitshares-core/tests/tests/operation_tests.cpp:1758:7: note: in expansion of macro ‘REQUIRE_THROW_WITH_VALUE’
       REQUIRE_THROW_WITH_VALUE(op, new_issuer, test.issuer);
       ^

In file included from /home/ubuntu/bitshares-core-dev/libraries/fc/include/fc/variant_object.hpp:2:0,
                 from /home/ubuntu/bitshares-core-dev/libraries/fc/include/fc/log/log_message.hpp:8,
                 from /home/ubuntu/bitshares-core-dev/libraries/fc/include/fc/log/logger.hpp:5,
                 from /home/ubuntu/bitshares-core-dev/libraries/fc/include/fc/exception/exception.hpp:6,
                 from /home/ubuntu/bitshares-core-dev/libraries/fc/include/fc/safe.hpp:2,
                 from /home/ubuntu/bitshares-core-dev/libraries/fc/include/fc/io/raw_fwd.hpp:7,
                 from /home/ubuntu/bitshares-core-dev/libraries/fc/include/fc/io/enum_type.hpp:3,
                 from /home/ubuntu/bitshares-core-dev/libraries/protocol/include/graphene/protocol/types.hpp:42,
                 from /home/ubuntu/bitshares-core-dev/libraries/chain/include/graphene/chain/types.hpp:26,
                 from /home/ubuntu/bitshares-core-dev/libraries/chain/include/graphene/chain/account_object.hpp:26,
                 from /home/ubuntu/bitshares-core-dev/libraries/chain/market_evaluator.cpp:24:
/home/ubuntu/bitshares-core-dev/libraries/fc/include/fc/variant.hpp: In member function ‘graphene::db::object_id_type graphene::chain::call_order_update_evaluator::do_apply(const graphene::protocol::call_order_update_operation&)’:
/home/ubuntu/bitshares-core-dev/libraries/fc/include/fc/variant.hpp:634:17: warning: ‘old_debt.fc::safe<long int>::value’ may be used uninitialized in this function [-Wmaybe-uninitialized]
       to_variant( static_cast<T>(s.value), v, max_depth );
                 ^
/home/ubuntu/bitshares-core-dev/libraries/chain/market_evaluator.cpp:316:25: note: ‘old_debt.fc::safe<long int>::value’ was declared here
    optional<share_type> old_debt;
                         ^

Build Environment Details about the build environment, including the relevant required libraries. Much of this information can be found in the CMakeFiles/CMakeOutput.log.

• Host OS: [Ubuntu 18.04 / 16.04 LTS]
• Host Physical RAM -
• Source Branch/Tag: 5.2.1
• OpenSSL Version: 1.1.1 / 1.0.2
• Boost Version: 1.65.1 / 1.58
• C++ Compiler: gcc version 7.5.0 / 5.4.0

CORE TEAM TASK LIST

• [ ] Evaluate Build Error
• [ ] Provide build guidance
• [ ] Create Bug Report

[abitmore]

It looks like this is because we don't have a to_variant function for the optional class.

[abitmore]

Update:

• With Ubuntu 20.04 and GCC 9.4.0, Release build, none of these warnings appears, instead, there are warnings complaining ‘*((void*)& op +64)’ of call_order_update_operation may be used uninitialized, which seems to be the optional<uint16_t> target_collateral_ratio field in the extensions field. No such warnings in Debug build.
• With Ubuntu 18.04 and GCC 7.5.0, Release build, the optional<uint64_t> sub_asset_creation_fee warning doesn't appear, but the other two both appear. No such warnings in Debug build.
• With Ubuntu 16.04 and GCC 5.4.0, Release build,
  • the warning about operation_tests doesn't appear,
  • adding a to_variant function for optional fixes the optional<uint64_t> sub_asset_creation_fee warning, but the optional<share_type> old_debt warning is still there.