build warnings in outputtype.cpp: may be used uninitialized #29359

Is there an existing issue for this?

• I have searched the existing issues

Current behaviour

Building Bitcoin Core from source using official instructions from https://github.com/bitcoin/bitcoin/blob/master/doc/build-unix.md I got compilation warnings, complaining about may be used uninitialized variables in two destructors.

Log of make -j 10: bitcoin-compilation-warning-master.txt

Expected behaviour

I expect no compilation warnings to be produced.

Steps to reproduce

Checkout master branch of bitcoin repo on Debian stable machine, install dependencies and build.

$ g++ --version
g++ (Debian 12.2.0-14) 12.2.0
Copyright (C) 2022 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

sudo apt-get install build-essential libtool autotools-dev automake pkg-config bsdmainutils python3
sudo apt-get install libevent-dev libboost-dev
sudo apt install libsqlite3-dev

make -C depends NO_BOOST=1 NO_LIBEVENT=1 NO_QT=1 NO_SQLITE=1 NO_NATPMP=1 NO_UPNP=1 NO_ZMQ=1 NO_USDT=1
export BDB_PREFIX=/root/bitcoin/depends/aarch64-unknown-linux-gnu/

./autogen.sh
./configure BDB_LIBS="-L${BDB_PREFIX}/lib -ldb_cxx-4.8" BDB_CFLAGS="-I${BDB_PREFIX}/include"
make -j 10

Relevant log output

No response

How did you obtain Bitcoin Core

Compiled from source

What version of Bitcoin Core are you using?

master@0b768746ef2c089676e3be30eb84e722a91453f6

Operating system and version

Debian GNU/Linux 12 (bookworm), Linux server 6.1.0-13-arm64 #1 SMP Debian 6.1.55-1 (2023-09-29) aarch64 GNU/Linux

Machine specifications

No response

I guess regardless of the g++ version used on Ubuntu or Debian, some kind of false positive warnings will be printed. I wonder why g++ on other distros does not print those warnings.

I wonder why g++ on other distros does not print those warnings.

I see the same if I use a similar GCC on a different distro, i.e Alpine 3.18 with GCC g++ (Alpine 12.2.1_git20220924-r10) 12.2.1 20220924):

  CXX      libbitcoin_common_a-protocol.o
In file included from ./hash.h:13,
                 from ./pubkey.h:10,
                 from ./addresstype.h:9,
                 from ./outputtype.h:9,
                 from outputtype.cpp:6:
In member function 'bool prevector<N, T, Size, Diff>::is_direct() const [with unsigned int N = 28; T = unsigned char; Size = unsigned int; Diff = int]',
    inlined from 'prevector<N, T, Size, Diff>::~prevector() [with unsigned int N = 28; T = unsigned char; Size = unsigned int; Diff = int]' at ./prevector.h:474:23,
    inlined from 'CScript::~CScript()' at ./script/script.h:413:7,
    inlined from 'CNoDestination::~CNoDestination()' at ./addresstype.h:18:7,
    inlined from 'constexpr void std::destroy_at(_Tp*) [with _Tp = CNoDestination]' at /usr/include/c++/12.2.1/bits/stl_construct.h:88:18,
    inlined from 'constexpr void std::_Destroy(_Tp*) [with _Tp = CNoDestination]' at /usr/include/c++/12.2.1/bits/stl_construct.h:149:22,
    inlined from 'std::__detail::__variant::_Variant_storage<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::_M_reset()::<lambda(auto:19&&)> mutable [with auto:19 = CNoDestination&]' at /usr/include/c++/12.2.1/variant:472:19,
    inlined from 'constexpr _Res std::__invoke_impl(__invoke_other, _Fn&&, _Args&& ...) [with _Res = void; _Fn = __detail::__variant::_Variant_storage<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::_M_reset()::<lambda(auto:19&&)>; _Args = {CNoDestination&}]' at /usr/include/c++/12.2.1/bits/invoke.h:61:36,
    inlined from 'constexpr std::enable_if_t<is_invocable_r_v<_Res, _Callable, _Args ...>, _Res> std::__invoke_r(_Callable&&, _Args&& ...) [with _Res = void; _Callable = __detail::__variant::_Variant_storage<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::_M_reset()::<lambda(auto:19&&)>; _Args = {CNoDestination&}]' at /usr/include/c++/12.2.1/bits/invoke.h:111:28,
    inlined from 'static constexpr decltype(auto) std::__detail::__variant::__gen_vtable_impl<std::__detail::__variant::_Multi_array<_Result_type (*)(_Visitor, _Variants ...)>, std::integer_sequence<long unsigned int, __indices ...> >::__visit_invoke(_Visitor&&, _Variants ...) [with _Result_type = void; _Visitor = std::__detail::__variant::_Variant_storage<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::_M_reset()::<lambda(auto:19&&)>&&; _Variants = {std::variant<CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>&}; long unsigned int ...__indices = {0}]' at /usr/include/c++/12.2.1/variant:1035:40,
    inlined from 'constexpr decltype(auto) std::__do_visit(_Visitor&&, _Variants&& ...) [with _Result_type = void; _Visitor = __detail::__variant::_Variant_storage<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::_M_reset()::<lambda(auto:19&&)>; _Variants = {variant<CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>&}]' at /usr/include/c++/12.2.1/variant:1788:5,
    inlined from 'constexpr decltype(auto) std::__do_visit(_Visitor&&, _Variants&& ...) [with _Result_type = void; _Visitor = __detail::__variant::_Variant_storage<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::_M_reset()::<lambda(auto:19&&)>; _Variants = {variant<CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>&}]' at /usr/include/c++/12.2.1/variant:1729:5,
    inlined from 'constexpr void std::__detail::__variant::_Variant_storage<false, _Types ...>::_M_reset() [with _Types = {CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown}]' at /usr/include/c++/12.2.1/variant:470:23,
    inlined from 'constexpr std::__detail::__variant::_Variant_storage<false, _Types ...>::~_Variant_storage() [with _Types = {CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown}]' at /usr/include/c++/12.2.1/variant:480:17,
    inlined from 'constexpr std::__detail::__variant::_Copy_ctor_base<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::~_Copy_ctor_base()' at /usr/include/c++/12.2.1/variant:554:12,
    inlined from 'constexpr std::__detail::__variant::_Move_ctor_base<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::~_Move_ctor_base()' at /usr/include/c++/12.2.1/variant:591:12,
    inlined from 'constexpr std::__detail::__variant::_Copy_assign_base<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::~_Copy_assign_base()' at /usr/include/c++/12.2.1/variant:629:12,
    inlined from 'constexpr std::__detail::__variant::_Move_assign_base<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::~_Move_assign_base()' at /usr/include/c++/12.2.1/variant:681:12,
    inlined from 'constexpr std::__detail::__variant::_Variant_base<CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::~_Variant_base()' at /usr/include/c++/12.2.1/variant:735:12,
    inlined from 'constexpr std::variant<_Types>::~variant() [with _Types = {CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown}]' at /usr/include/c++/12.2.1/variant:1407:28,
    inlined from 'std::vector<std::variant<CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown> > GetAllDestinationsForKey(const CPubKey&)' at outputtype.cpp:79:5:
./prevector.h:175:37: warning: '*(const prevector<28, unsigned char, unsigned int, int>*)((char*)&p2sh + offsetof(std::CTxDestination, std::variant<CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::<unnamed>.std::__detail::__variant::_Variant_base<CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::<unnamed>.std::__detail::__variant::_Move_assign_base<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::<unnamed>.std::__detail::__variant::_Copy_assign_base<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::<unnamed>.std::__detail::__variant::_Move_ctor_base<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::<unnamed>.std::__detail::__variant::_Copy_ctor_base<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::<unnamed>.std::__detail::__variant::_Variant_storage<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::_M_u)).prevector<28, unsigned char>::_size' may be used uninitialized [-Wmaybe-uninitialized]
  175 |     bool is_direct() const { return _size <= N; }
      |                                     ^~~~~
outputtype.cpp: In function 'std::vector<std::variant<CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown> > GetAllDestinationsForKey(const CPubKey&)':
outputtype.cpp:77:24: note: 'p2sh' declared here
   77 |         CTxDestination p2sh = ScriptHash(GetScriptForDestination(segwit));
      |                        ^~~~
In file included from /usr/include/c++/12.2.1/vector:64,
                 from ./serialize.h:25,
                 from ./hash.h:14:
In destructor 'constexpr std::_Vector_base<_Tp, _Alloc>::~_Vector_base() [with _Tp = unsigned char; _Alloc = std::allocator<unsigned char>]',
    inlined from 'constexpr std::vector<_Tp, _Alloc>::~vector() [with _Tp = unsigned char; _Alloc = std::allocator<unsigned char>]' at /usr/include/c++/12.2.1/bits/stl_vector.h:733:7,
    inlined from 'constexpr WitnessUnknown::~WitnessUnknown()' at ./addresstype.h:94:8,
    inlined from 'constexpr void std::destroy_at(_Tp*) [with _Tp = WitnessUnknown]' at /usr/include/c++/12.2.1/bits/stl_construct.h:88:18,
    inlined from 'constexpr void std::_Destroy(_Tp*) [with _Tp = WitnessUnknown]' at /usr/include/c++/12.2.1/bits/stl_construct.h:149:22,
    inlined from 'std::__detail::__variant::_Variant_storage<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::_M_reset()::<lambda(auto:19&&)> mutable [with auto:19 = WitnessUnknown&]' at /usr/include/c++/12.2.1/variant:472:19,
    inlined from 'constexpr _Res std::__invoke_impl(__invoke_other, _Fn&&, _Args&& ...) [with _Res = void; _Fn = __detail::__variant::_Variant_storage<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::_M_reset()::<lambda(auto:19&&)>; _Args = {WitnessUnknown&}]' at /usr/include/c++/12.2.1/bits/invoke.h:61:36,
    inlined from 'constexpr std::enable_if_t<is_invocable_r_v<_Res, _Callable, _Args ...>, _Res> std::__invoke_r(_Callable&&, _Args&& ...) [with _Res = void; _Callable = __detail::__variant::_Variant_storage<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::_M_reset()::<lambda(auto:19&&)>; _Args = {WitnessUnknown&}]' at /usr/include/c++/12.2.1/bits/invoke.h:111:28,
    inlined from 'static constexpr decltype(auto) std::__detail::__variant::__gen_vtable_impl<std::__detail::__variant::_Multi_array<_Result_type (*)(_Visitor, _Variants ...)>, std::integer_sequence<long unsigned int, __indices ...> >::__visit_invoke(_Visitor&&, _Variants ...) [with _Result_type = void; _Visitor = std::__detail::__variant::_Variant_storage<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::_M_reset()::<lambda(auto:19&&)>&&; _Variants = {std::variant<CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>&}; long unsigned int ...__indices = {7}]' at /usr/include/c++/12.2.1/variant:1035:40,
    inlined from 'constexpr decltype(auto) std::__do_visit(_Visitor&&, _Variants&& ...) [with _Result_type = void; _Visitor = __detail::__variant::_Variant_storage<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::_M_reset()::<lambda(auto:19&&)>; _Variants = {variant<CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>&}]' at /usr/include/c++/12.2.1/variant:1795:5,
    inlined from 'constexpr void std::__detail::__variant::_Variant_storage<false, _Types ...>::_M_reset() [with _Types = {CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown}]' at /usr/include/c++/12.2.1/variant:470:23,
    inlined from 'constexpr std::__detail::__variant::_Variant_storage<false, _Types ...>::~_Variant_storage() [with _Types = {CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown}]' at /usr/include/c++/12.2.1/variant:480:17,
    inlined from 'constexpr std::__detail::__variant::_Copy_ctor_base<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::~_Copy_ctor_base()' at /usr/include/c++/12.2.1/variant:554:12,
    inlined from 'constexpr std::__detail::__variant::_Move_ctor_base<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::~_Move_ctor_base()' at /usr/include/c++/12.2.1/variant:591:12,
    inlined from 'constexpr std::__detail::__variant::_Copy_assign_base<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::~_Copy_assign_base()' at /usr/include/c++/12.2.1/variant:629:12,
    inlined from 'constexpr std::__detail::__variant::_Move_assign_base<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::~_Move_assign_base()' at /usr/include/c++/12.2.1/variant:681:12,
    inlined from 'constexpr std::__detail::__variant::_Variant_base<CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::~_Variant_base()' at /usr/include/c++/12.2.1/variant:735:12,
    inlined from 'constexpr std::variant<_Types>::~variant() [with _Types = {CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown}]' at /usr/include/c++/12.2.1/variant:1407:28,
    inlined from 'std::vector<std::variant<CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown> > GetAllDestinationsForKey(const CPubKey&)' at outputtype.cpp:79:5:
/usr/include/c++/12.2.1/bits/stl_vector.h:367:31: warning: '*(std::_Vector_base<unsigned char, std::allocator<unsigned char> >*)((char*)&p2sh + offsetof(std::CTxDestination, std::variant<CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::<unnamed>.std::__detail::__variant::_Variant_base<CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::<unnamed>.std::__detail::__variant::_Move_assign_base<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::<unnamed>.std::__detail::__variant::_Copy_assign_base<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::<unnamed>.std::__detail::__variant::_Move_ctor_base<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::<unnamed>.std::__detail::__variant::_Copy_ctor_base<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::<unnamed>.std::__detail::__variant::_Variant_storage<false, CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown>::_M_u) + 8).std::_Vector_base<unsigned char, std::allocator<unsigned char> >::_M_impl.std::_Vector_base<unsigned char, std::allocator<unsigned char> >::_Vector_impl::<anonymous>.std::_Vector_base<unsigned char, std::allocator<unsigned char> >::_Vector_impl_data::_M_end_of_storage' may be used uninitialized [-Wmaybe-uninitialized]
  367 |                       _M_impl._M_end_of_storage - _M_impl._M_start);
      |                       ~~~~~~~~^~~~~~~~~~~~~~~~~
outputtype.cpp: In function 'std::vector<std::variant<CNoDestination, PubKeyDestination, PKHash, ScriptHash, WitnessV0ScriptHash, WitnessV0KeyHash, WitnessV1Taproot, WitnessUnknown> > GetAllDestinationsForKey(const CPubKey&)':
outputtype.cpp:77:24: note: 'p2sh' declared here
   77 |         CTxDestination p2sh = ScriptHash(GetScriptForDestination(segwit));
      |                        ^~~~
  CXX      libbitcoin_common_a-psbt.o

I see the same if I use a similar GCC on a different distro, i.e Alpine 3.18 with GCC g++ (Alpine 12.2.1_git20220924-r10) 12.2.1 20220924):

Interesting. alpine:latest with g++-13.2.1 looked fine for me: https://cirrus-ci.com/task/4994174227841024?logs=make#L5

However, on Ubuntu, g++-13.2.0 had some warnings: https://cirrus-ci.com/task/4712699251130368?logs=make#L173

Edit: The reason is that the Ubuntu run was using asan.

This is an upstream issue and will be solved next time you upgrade your toolchain.

Closing for now. Leave a comment if you want this re-opened.