[huangminghuang]

Signal chaining can call a legacy handler through the wrong ABI in the OC executor, or treat SIG_IGN/SIG_DFL as callback addresses when SA_SIGINFO is set. Preserve each predecessor's calling convention and consume the merged non-OC fix directly from eos-vm.

• Add a typed OC predecessor adapter, reject sentinel dispositions before decoding the callback union, and initialize both sigaction structures. Keep the executor's existing default-fault fallback.
• Add libraries/sys-vm as a submodule pinned to 2c8d4b283b500f56241450bdc60a594455a972d9, the merged eos-vm #16. Remove the wire-sys-vm vcpkg dependency, version override, registry entry, and package lookups. Softfloat remains a vcpkg dependency; no VM registry revision is needed.
• Integrate the header-only VM target with source/install include paths and C++20 requirements. Isolate its standalone test/tool, compiler-launcher, profiling, sanitizer, and installation settings from Sysio, preserving shared dependent-option cache values. Ship VM headers/CMake exports in the development component and its license in the runtime component.
• Update submodule initialization instructions. Add a CMake integration regression that builds and runs source-tree and installed consumers, verifies option isolation and component separation, and checks the missing-submodule diagnostic.
• Register the OC signal regression once, exclude it from per-runtime discovery, and retain it in the CI/coverage filter. Remove the redundant end anchor that broke the coverage target under Ninja and Make.

Validation:

• Fresh Clang 18 Release configure and complete native build pass. The new vcpkg installation contains neither the VM port nor old VM headers; runtime compilation resolves libraries/sys-vm/include. Of the 42 VM headers, only signals.hpp differs from the previous package.
• Integration/SDK regression passes with Clang/Ninja, GCC 14.2/Make, and Clang/Ninja Multi-Config. A fresh checkout fetches the exact merged submodule commit and passes the same regression.
• Full Sysio dev/base staging checks the VM header hash, CMake export, component separation, and license; an exported-target consumer builds and runs with the vcpkg softfloat package.
• The merged VM signal probe passes Clang ASan, UBSan, and function-call sanitization. clangd checks the interpreter translation unit with zero errors; the complete PR diff passes whitespace checks.
• The OC adapter's isolated regression passes 3 cases / 15 assertions under GCC 14.2 and Clang 18, including Clang UBSan/function sanitization. Registration checks cover both three-runtime and interpreter-only configurations. The actual coverage block builds and executes its selected CTest entries under Ninja and Make with report tools stubbed.
• The upstream eos-vm change passed all 269 VM cases / 1,506 assertions plus focused GCC and sanitizer regressions before merge.
• Full native suites pass: interpreter chain 1,729 cases / 1,359,774 assertions; plugin 321 / 60,790; contracts 1,090 / 481,935; FC 752 / 5,014,808.
• All 28 selected CTest entries pass, covering JIT/OC WASM/configuration and deadline tests, OC limits/interrupts, OC execution without FSGSBASE, the signal regression, and both CMake regressions.

[heifner]

wire-sys-vm's chain_previous_signal_handler has the second of these defects: it tests SA_SIGINFO first and calls sa_sigaction without checking for SIG_IGN / SIG_DFL. It is what decodes the predecessor on a node without OC, so it is worth the same fix there.

[huangminghuang]

The non-OC sentinel issue is reproduced and fixed in Wire-Network/eos-vm#16. The new tests fail against the original header and pass with GCC 14 and Clang sanitizers; the complete VM unit suite passes 269 cases. A registry port revision will be needed after that fix merges to bring it into Sysio.