Python extension Linux: build RHEL9-portable (GCC 11 + static Boost/libstdc++)

[SicongLiu2000]

Summary

The SQL Server Python language extension ships as a single Linux shared object (libPythonExtension.so) that SQL Server loads at runtime across every supported distro. This PR makes that .so portable down to RHEL 9 — our oldest in-support Linux baseline — while keeping it loadable on all newer distros (RHEL 10, Ubuntu 22.04/24.04, Azure Linux 3). It does so by pinning the build toolchain and self-containing the extension's C++/Boost dependencies, with no change to extension behavior or its public surface.

Background & motivation

A language extension is only useful if it loads on the customer's distro. Because a single artifact is shipped to all of them, it must reference only symbols present on the lowest common baseline (RHEL 9 — glibc 2.34). Built on the newer default image, the extension picked up newer glibc/libstdc++ symbol versions that RHEL 9 does not provide, so it failed to load there. The goal of this change is a single, self-contained .so whose external contract is limited to the RHEL 9 baseline.

Approach

Two complementary changes, both confined to the Python extension's Linux build:

1. Pin the compiler to GCC 11. We build the extension with GCC 11 because we need to support RHEL 9. GCC 11 is native to the Ubuntu 22.04 build image and produces a libstdc++/glibc symbol floor compatible with RHEL 9 and everything newer.

2. Self-contain the C++/Boost dependencies. Statically link libstdc++/libgcc and Boost (Boost.Python / Boost.NumPy) into the extension so the shipped .so carries no external libstdc++ or Boost runtime dependency. This removes the whole class of "works on the build image, missing on the target distro" load failures rather than papering over one symbol.

Changes

• restore-packages.sh — install/use GCC 11 instead of GCC 13 for the extension build.
• language-extensions/python/src/CMakeLists.txt
  • Static-link libstdc++ / libgcc: -static-libstdc++ -static-libgcc -Wl,--exclude-libs,ALL — the .so no longer requires a newer system libstdc++ at load time.
  • Static-link Boost (.a via NO_DEFAULT_PATH) so the .so carries no external Boost dependency.

Net diff is small and localized to the Python extension's Linux link/toolchain; the extension's code, ABI to SQL Server, and Python 3.12 runtime are unchanged.

Verification

ELF (link-level, the contract we actually ship):

• DT_NEEDED = libpython3.12 + libc / ld-linux only — zero Boost, no libstdc++.
• No GLIBCXX version dependency at all.
• Max referenced GLIBC = 2.34 (the RHEL 9 baseline).

End-to-end (PVS PythonExtension suite, per distro):

• Ubuntu 22.04/24.04, RHEL 9, RHEL 10 — all green, full pass counts, 0 causality fail-warnings.

Risk / compatibility

• No functional or API change — same extension, same Python 3.12, same behavior; only the link/toolchain baseline moves down.
• Static-linking libstdc++/libgcc/Boost slightly increases the .so size but eliminates runtime dependency drift across distros — a net reliability win for shipping one artifact everywhere.

[Copilot]

Pull request overview

This PR updates the Linux build/link configuration for the SQL Server Python language extension (libPythonExtension.so) to improve binary portability down to the RHEL 9 baseline by lowering toolchain/libstdc++ symbol requirements and eliminating runtime Boost dependencies.

Changes:

• Switch the Linux build toolchain to GCC 11 via package restore/setup.
• Statically link libstdc++/libgcc into the extension and hide those symbols from interposition.
• Force static Boost.Python / Boost.NumPy linkage from the provided Boost build root to avoid external Boost .so dependencies.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
restore-packages.sh	Pins the build compiler to GCC 11 via apt + update-alternatives.
language-extensions/python/src/CMakeLists.txt	Updates Linux linker flags for static libstdc++/libgcc and switches Boost discovery to static archives.

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