type: Accept any comparator, hash, and allocator in container fields #379

pull ryanofsky wants to merge 1 commits into bitcoin-core:master from ryanofsky:pr/containers changing 7 files +41 −16

ryanofsky commented at 7:34 AM on October 15, 2026: collaborator

Problem: std::vector, std::set, std::map and std::unordered_set fields and parameters only work when they use the default comparator, hash and allocator types. Anything else, like Bitcoin Core's GCSFilter::ElementSet (std::unordered_set<Element, ByteVectorHash>), fails to compile with "no matching function for call to CustomBuildField". Bitcoin Core currently works around this by copying the std::unordered_set read and build functions into its own code (bitcoin/bitcoin#29409).

Solution: Make the container overloads in type-vector.h, type-set.h, type-map.h and type-unordered-set.h templates over the containers' comparator, hash and allocator types. Small change to the four headers, plus a FooStruct round-trip test with a descending std::set and std::map, an std::unordered_set with a custom hash, and a std::pmr::vector.

type: Accept any comparator, hash, and allocator in container fields

Let std::vector, std::set, std::map, and std::unordered_set fields use any
comparator, hash, or allocator type, instead of only matching containers
with the default template arguments. Previously, a field like Bitcoin Core's
GCSFilter::ElementSet (std::unordered_set<Element, ByteVectorHash>) didn't
match any overload, so Bitcoin Core had to copy the std::unordered_set read
and build functions to pass it over IPC.

This change was written with Claude Opus 5.5 (1M context).

9a42d0065d

DrahtBot commented at 7:35 AM on October 15, 2026: none



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xyzconstant commented at 4:29 PM on October 27, 2026: contributor

ACK 9a42d0065d9a012b6cdaa7780cf2464f473ed2cd

This allows container fields to use non-default comparator, hash, and allocator types. Needed for bitcoin/bitcoin#29409 where Chain::blockFilterMatchesAny takes a GCSFilter::ElementSet (std::unordered_set<Element, ByteVectorHash>).

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type: Accept any comparator, hash, and allocator in container fields #379

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