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Fix Bitcoin Core build errors from libmultiprocess headers - #370
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Declare SocketError as an inline variable so the header does not define a separate internal-linkage copy in every translation unit that includes it. Bitcoin Core's build now enables -Wunused-const-variable (bitcoin/bitcoin#36275), which with GCC warns about unused const variables defined in headers and fails the build with -Werror in every file that includes mp/util.h without using SocketError. Bitcoin Core made the same change to its own SocketError definition in bitcoin/bitcoin#35852. This change was written with Claude Opus 5.5 (1M context).
Bitcoin Core builds the libmultiprocess subtree with -Wunused-const-variable (bitcoin/bitcoin#36275). With GCC this warns about unused const variables defined in headers, so a header-level constexpr that is not inline breaks the Bitcoin Core build. Enable it in the GCC-based CI configs to catch this here first. Clang's -Wunused-const-variable does not warn about variables defined in headers, so it is not added to the clang configs. This change was written with Claude Opus 5.5 (1M context).
Check that KJ_NO_EXCEPTIONS is defined before testing its value. Bitcoin Core builds the libmultiprocess subtree with -Wundef, so the plain `#if KJ_NO_EXCEPTIONS` check added in bitcoin-core#364 fails the build with -Werror whenever the macro is not defined, which is the normal case. This change was written with Claude Opus 5.5 (1M context).
Bitcoin Core builds the libmultiprocess subtree with -Wundef, so a preprocessor check on an undefined macro breaks the Bitcoin Core build. Enable it in one GCC and one clang config to catch this here first. This change was written with Claude Opus 5.5 (1M context).
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lgtm ACK 3577d23 |
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tACK 3577d23
Confirmed Bitcoin Core builds with libmultiprocess with these changes
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ACK 3577d23 |
This was referenced Oct 7, 2026
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Backport of bitcoin-core/libmultiprocess#370. Import only the two header fixes so the subtree builds with -Wundef and -Wunused-const-variable enabled as errors. The upstream CI changes are not included.
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ACK 3577d23 Reviewed commit by commit, LGTM. |
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Sync with upstream master after bitcoin-core/libmultiprocess#370 landed. The header fixes were already imported by sv2-tp#134; this update adds the upstream CI warning flags and IWYU fixes from #371. Use the shared subtree exclusions in the shell locale linter so upstream scripts are not required to follow local locale conventions. Base the subtree merge on the previous import so the squash and merge commits remain reusable for backports.
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Sync with upstream master after bitcoin-core/libmultiprocess#370 landed. The header fixes were already imported by sv2-tp#134; this update adds the upstream CI warning flags and IWYU fixes from #371. Base the subtree merge on the previous import so the squash and merge commits remain reusable for backports.
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2e7812a5a1 Merge bitcoin-core/libmultiprocess#370: Fix Bitcoin Core build errors from libmultiprocess headers 686bccf766 Merge bitcoin-core/libmultiprocess#371: cmake: Fix silent include-what-you-use failures f0a14754ef cmake: Show include-what-you-use diagnostics when it fails 92127a984a cmake: Pass -w to include-what-you-use 3577d23f61 ci: Enable -Wundef in default and llvm jobs debd42955e proxy-types: Avoid -Wundef error when KJ_NO_EXCEPTIONS is not defined a8c64c7faa ci: Enable -Wunused-const-variable in GCC jobs 701449c165 util: Make SocketError inline constexpr REVERT: fcc569c2cf proxy-types: Avoid -Wundef error when KJ_NO_EXCEPTIONS is not defined REVERT: fdeefd7aab util: Make SocketError inline constexpr git-subtree-dir: src/ipc/libmultiprocess git-subtree-split: 2e7812a5a1ea8fada26f74b06be62e195a3783a5
This was referenced Oct 14, 2026
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Problem: Bumping the libmultiprocess subtree in Bitcoin Core to current master breaks the build with
-Werror. GCC reportsSocketErroras an unused const variable in every file that includesmp/util.hwithout using it (-Wunused-const-variable, enabled by bitcoin/bitcoin#36275; CI failure), and the#if KJ_NO_EXCEPTIONScheck added in #364 fails-Wundefwhen the macro is not defined.Solution: Make
SocketErroraninline constexprvariable, the same change Bitcoin Core made to its ownSocketErrorin bitcoin/bitcoin#35852, and checkdefined(KJ_NO_EXCEPTIONS)before testing its value. Also enable both warnings in CI here (-Wunused-const-variablein the GCC configs,-Wundefin default and llvm) so these problems are caught before a subtree update. Details are in the commit messages.