Build error (boost::multi_index_container) #35415

Is there an existing issue for this?

• I have searched the existing issues

Current behaviour

I fail to build Core from source on archlinux. The error presents itself across all files declaring multi indexed containers, in similar fashion:

bitcoin/src/node/txorphanage.cpp:94:54: error: invalid use of incomplete type ‘struct boost::multi_index::indexed_by<boost::multi_index::ordered_unique<boost::multi_index::tag<node::TxOrphanageImpl::ByWtxid>, node::TxOrphanageImpl::WtxidExtractor>, boost::multi_index::ordered_unique<boost::multi_index::tag<node::TxOrphanageImpl::ByPeer>, node::TxOrphanageImpl::ByPeerViewExtractor, void> >’

I've reproduced this across tags 0.29.x, 0.30.x and 0.31.0. I did not check with tags. In 0.31.0, it happens in:

• txmempool.h:214
• txrequest.cpp:211
• txorphanage.cpp:94

It seems the compiler refuses to expand the template on the indexer struct declaration. For example, in txorphanage.cpp, the struct is:

    struct OrphanIndices final : boost::multi_index::indexed_by<
        boost::multi_index::ordered_unique<boost::multi_index::tag<ByWtxid>, WtxidExtractor>,
        boost::multi_index::ordered_unique<boost::multi_index::tag<ByPeer>, ByPeerViewExtractor>
    >{};

Replacing the struct by a using statement fixes the issue in all instances, as such:

    using OrphanIndices = boost::multi_index::indexed_by<
        boost::multi_index::ordered_unique<boost::multi_index::tag<ByWtxid>, WtxidExtractor>,
        boost::multi_index::ordered_unique<boost::multi_index::tag<ByPeer>, ByPeerViewExtractor>
    >;

I've searched issues and PRs a little and failed to find notable mentions of this build error. There is a secondary mention of CI failing to run a test in PR #35147, where the issue appears to be a compilation failure like I have experienced. This is blamed on an out of date boost version, but mine is up to date. This is on a brand new arch install (changed the SSD to get a local copy of the blockchain).

Expected behaviour

I do not expect anything, I don't know how else to report this possibly benign build error (I'm likely alone in experiencing it).

Steps to reproduce

These are what I believe to be relevant system components to reproduce this issue:

uname -srm
Linux 7.0.10-arch1-1 x86_64

gcc --version     
gcc (GCC) 16.1.1 20260430

pacman -Q boost
boost 1.91.0-1

pacman -Q cmake
cmake 4.3.3-1

Relevant log output

No response

How did you obtain Bitcoin Core

Compiled from source

What version of Bitcoin Core are you using?

v0.31.0

Operating system and version

Linux 7.0.10-arch1-1 x86_64

Machine specifications

uname -srm
Linux 7.0.10-arch1-1 x86_64

gcc --version     
gcc (GCC) 16.1.1 20260430

pacman -Q boost
boost 1.91.0-1

pacman -Q cmake
cmake 4.3.3-1

Acer laptop with a AMD 5700U, 16GB RAM and 2TB Samsung SSD.

This was fixed in #35175, and backported into all maintained branches, however we haven't cut new releases for those branches yet.

Thanks, closing the issue.