interface/wallet: get rid of missing initializer warnings #14774

Debian Jessie (PPC) gives me warnings, which go away with a default empty constructor in WalletTx:

[...]
  CXX      libbitcoin_server_a-validationinterface.o
  AR       libbitcoin_server.a
  CXX      interfaces/libbitcoin_wallet_a-wallet.o
interfaces/wallet.cpp: In member function ‘virtual interfaces::WalletTx interfaces::{anonymous}::WalletImpl::getWalletTx(const uint256&)’:
interfaces/wallet.cpp:306:17: warning: missing initializer for member ‘interfaces::WalletTx::tx’ [-Wmissing-field-initializers]
         return {};
                 ^
interfaces/wallet.cpp:306:17: warning: missing initializer for member ‘interfaces::WalletTx::txin_is_mine’ [-Wmissing-field-initializers]
interfaces/wallet.cpp:306:17: warning: missing initializer for member ‘interfaces::WalletTx::txout_is_mine’ [-Wmissing-field-initializers]
interfaces/wallet.cpp:306:17: warning: missing initializer for member ‘interfaces::WalletTx::txout_address’ [-Wmissing-field-initializers]
interfaces/wallet.cpp:306:17: warning: missing initializer for member ‘interfaces::WalletTx::txout_address_is_mine’ [-Wmissing-field-initializers]
interfaces/wallet.cpp:306:17: warning: missing initializer for member ‘interfaces::WalletTx::credit’ [-Wmissing-field-initializers]
interfaces/wallet.cpp:306:17: warning: missing initializer for member ‘interfaces::WalletTx::debit’ [-Wmissing-field-initializers]
interfaces/wallet.cpp:306:17: warning: missing initializer for member ‘interfaces::WalletTx::change’ [-Wmissing-field-initializers]
interfaces/wallet.cpp:306:17: warning: missing initializer for member ‘interfaces::WalletTx::time’ [-Wmissing-field-initializers]
interfaces/wallet.cpp:306:17: warning: missing initializer for member ‘interfaces::WalletTx::value_map’ [-Wmissing-field-initializers]
interfaces/wallet.cpp:306:17: warning: missing initializer for member ‘interfaces::WalletTx::is_coinbase’ [-Wmissing-field-initializers]
interfaces/wallet.cpp: In member function ‘virtual interfaces::WalletTx interfaces::{anonymous}::WalletImpl::getWalletTxDetails(const uint256&, interfaces::WalletTxStatus&, interfaces::WalletOrderForm&, bool&, int&)’:
interfaces/wallet.cpp:355:17: warning: missing initializer for member ‘interfaces::WalletTx::tx’ [-Wmissing-field-initializers]
         return {};
                 ^
interfaces/wallet.cpp:355:17: warning: missing initializer for member ‘interfaces::WalletTx::txin_is_mine’ [-Wmissing-field-initializers]
interfaces/wallet.cpp:355:17: warning: missing initializer for member ‘interfaces::WalletTx::txout_is_mine’ [-Wmissing-field-initializers]
interfaces/wallet.cpp:355:17: warning: missing initializer for member ‘interfaces::WalletTx::txout_address’ [-Wmissing-field-initializers]
interfaces/wallet.cpp:355:17: warning: missing initializer for member ‘interfaces::WalletTx::txout_address_is_mine’ [-Wmissing-field-initializers]
interfaces/wallet.cpp:355:17: warning: missing initializer for member ‘interfaces::WalletTx::credit’ [-Wmissing-field-initializers]
interfaces/wallet.cpp:355:17: warning: missing initializer for member ‘interfaces::WalletTx::debit’ [-Wmissing-field-initializers]
interfaces/wallet.cpp:355:17: warning: missing initializer for member ‘interfaces::WalletTx::change’ [-Wmissing-field-initializers]
interfaces/wallet.cpp:355:17: warning: missing initializer for member ‘interfaces::WalletTx::time’ [-Wmissing-field-initializers]
interfaces/wallet.cpp:355:17: warning: missing initializer for member ‘interfaces::WalletTx::value_map’ [-Wmissing-field-initializers]
interfaces/wallet.cpp:355:17: warning: missing initializer for member ‘interfaces::WalletTx::is_coinbase’ [-Wmissing-field-initializers]
  CXX      wallet/libbitcoin_wallet_a-coincontrol.o
[...]

@kallewoof does it work if you replace return {}; with WalletTx(); instead?

I think this is fixed in GCC 5 and above, fyi: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=36750

@promag

@kallewoof does it work if you replace return {}; with WalletTx(); instead?

Yes, that works. A one-line fix-all seems more convenient, though.

I thought we don't fix or work around false warnings of broken compilers?

@MarcoFalke It's the latest version on Debian Jessie, which seems to have long term support from the Debian people (i.e. it is not yet out of its life cycle).

I'm neutral on abandoning it. I think we should abandon old Red Hat distros too and switch to C++14 already, while at it (slightly off topic, but still relevant).

(Edit: should note that I specifically run this because it's the newest Debian which runs on a Big Endian PowerPC system, and I wanted to test bitcoin on Big Endian systems. Upgrading is not an option here.)