[sunsided]

A suggestion for fixing #1381.

Problem

The Linux prebuilt static liblbug.a is compiled with gcc-toolset-13 (manylinux_2_28). Consumers link it next to their own C++ code, for example the Rust crate's cxx bridge, which they compile with their GCC. Both sides define the same libstdc++ template instantiations (std::format, std::string, …) as COMDAT groups, and the linker keeps only one copy per group. On a system with GCC 15 (Ubuntu 26.04, today's GitHub ubuntu-latest), the archive's GCC 13 code ends up calling the consumer's GCC 15 std::format internals, and any COPY … TO segfaults in Binder::bindCopyToClause. Ubuntu 24.04 (GCC 13) is unaffected. Building from source works around it, but downstream builds then pay a large C++ compile.

Fix

A new option, LBUG_LOCALIZE_STATIC_SYMBOLS (default off, ELF targets only). When it's set, BundleStaticLibrary.cmake post-processes the bundled archive:

1. ld -r --force-group-allocation --whole-archive combines it into one object and turns COMDAT group members into ordinary sections, so the consumer's same-named group can't cause the archive's copy to be discarded.
2. objcopy --keep-global-symbol='*4lbug*' --keep-global-symbol='lbug_*' makes every defined global local except the lbug:: C++ API and the C API. The archive keeps private copies of its libstdc++ instantiations and bundled third-party code.
3. objcopy --weaken-symbols handles the remaining STB_GNU_UNIQUE definitions (function-local statics, inline variables), which objcopy can't localize and which would otherwise be duplicate symbols. Only defined symbols are weakened, because a weakened undefined reference would resolve to 0.

precompiled-bin-workflow.yml enables it for the Linux compat and perf static prebuilts. Default builds, and therefore developer builds and the existing test jobs, are unchanged.

Verification

I built the static archive with this patch applied to v0.21.2, using upstream's CMake in quay.io/pypa/manylinux_2_28_x86_64 with gcc-toolset-13 and openssl3. That's the same toolchain as the compat job, but configured directly with -DBUILD_SHELL=FALSE -DBUILD_SHARED_LBUG=FALSE -DLBUG_LOCALIZE_STATIC_SYMBOLS=TRUE. The result is one archive member, with 0 global std::__format definitions and 0 STB_GNU_UNIQUE symbols. I then used it as the Rust crate's prebuilt (LBUG_PREBUILT_CACHE_DIR):

Consumer	Stock v0.21.2 prebuilt	Patched prebuilt
Minimal COPY … TO repro from #1381, Ubuntu 26.04 / GCC 15.2	segfault (exit 139)	✅ exit 0
Same repro, Ubuntu 24.04 / GCC 13.3	✅	✅ exit 0
glyphtrail workspace tests (608, heavy lbug use), Ubuntu 26.04	segfault	✅ all pass

Not verified

• I didn't run your own e2e, extension or language-binding suites against the patched prebuilt. The default-off option doesn't change those builds.
• Loading extensions (INSTALL/LOAD EXTENSION) into a consumer linked with the patched archive is untested. Extensions resolve lbug::*, which stays global, so I expect no change, but it's worth a check.
• *4lbug* also keeps std templates instantiated over lbug types global (e.g. std::vector<lbug::common::Value>). Those can in principle still merge across GCC versions. Nothing in the tests above hit that.
• The perf variant (clang-21 + libstdc++) is enabled on the reasoning that it has the same exposure, but I didn't test it.

[Copilot]

🔵 Needs a closer look

It is a low-level linker/archive symbol-manipulation change affecting released prebuilt binaries, with several author-acknowledged unverified paths (perf variant, extension loading, std templates over lbug types), so it warrants human validation.

No open issues 🎉

What changed in this PR

This PR addresses issue #1381, where COPY … TO segfaults when the prebuilt static liblbug.a (built with gcc-toolset-13) is linked next to consumer C++ compiled with a newer GCC (e.g. GCC 15 on Ubuntu 26.04). Both sides emit the same libstdc++ template instantiations (std::format, std::string, …) as COMDAT groups; the linker keeps one copy, causing cross-ABI calls and a crash in Binder::bindCopyToClause. The fix adds an opt-in build option that post-processes the bundled archive so its internal (non-API) symbols become private, preventing cross-compiler merging. It is default-off, so developer and test builds are unchanged, and enabled only for the Linux compat and perf static prebuilts.

Changes:

• Adds LBUG_LOCALIZE_STATIC_SYMBOLS (ELF-only, default FALSE) and plumbs ld/objcopy/nm executables into the bundling script.
• Implements the localization pipeline in BundleStaticLibrary.cmake (combine into one object via ld -r --force-group-allocation --whole-archive, localize non-API globals, weaken remaining STB_GNU_UNIQUE definitions).
• Enables the option for the Linux compat and perf static prebuilt jobs.

File	Description
CMakeLists.txt	Declares the new LBUG_LOCALIZE_STATIC_SYMBOLS build option (default off).
src/​CMakeLists.txt	Adds an ELF-only guard and passes LOCALIZE_SYMBOLS, LD/OBJCOPY/NM executables to the post-build bundling command.
cmake/​BundleStaticLibrary.cmake	Adds the archive post-processing that makes internal symbols local and weakens remaining unique symbols.
.github/​workflows/​precompiled-bin-workflow.yml	Enables the option for the Linux compat and perf static prebuilt builds.

_{Review effort: Balanced}

[adsharma]

Defer to post-0.22.0 release. Keep it open for now.