SpliX 3.0.0: C++23 modernization, CMake, hardening, and tests

[dutch2005]

Summary

This is a single-commit SpliX 3.0.0 modernization proposal, rebased directly onto current OpenPrinting master (4854286). The previous multi-commit development history has been intentionally squashed so maintainers can review and test one coherent change.

Review map

• Build and packaging: replaces the legacy Makefiles with modular CMake 3.25 configuration, C++23 feature probing, CPack, Docker support, and Debian packaging for amd64, arm64, armhf, i386, and riscv64.
• Core modernization: introduces explicit result/error handling, modern ownership, portable synchronization, safer integer and buffer handling, and modular implementation units without removing printer-driver behavior.
• Protocol and reliability hardening: preserves SPL/QPDL output through characterization tests, fixes cache-controller synchronization and page ordering, and rejects new compiler diagnostics as errors.
• Tests and CI: adds sanitizer, compression, protocol, functional, concurrency, package-identity, and feature-probe coverage plus multi-architecture hosted builds.
• Documentation and attribution: identifies the proposal consistently as 3.0.0 and updates AUTHORS, README, BUILDING, CHANGELOG, architecture notes, security guidance, and release notes.

Commit structure

PR #22 intentionally contains exactly one commit:

8966ce3 feat: modernize SpliX for C++23 and 3.0.0

Author: Michael Maertzdorf (dutch2005) using the GitHub-linked email address.

Verification

• Exact final head: 8966ce338d9aef9f1023c4b6c69221b87d0a58f4
• OpenPrinting base: 4854286334346059e7fec6f5f2328a23fa5fa774
• Full hosted CI: https://github.com/dutch2005/splix/actions/runs/33100275214
• CodeQL C/C++ and Actions: https://github.com/dutch2005/splix/actions/runs/33100274586
• ASan/UBSan: 21/21 tests passed
• Compiler diagnostics: zero warning/error lines across the hosted matrix
• Packages: amd64, arm64, armhf, i386, and riscv64 artifacts produced from the exact final head
• LXC 9100 Docker (Debian stable): ASan/UBSan 21/21, no-thread 19/19, no-JBIG 20/20, and release amd64 .deb packaging passed on the identical final tree
• C++23 feature probe passed; the C++20 probe was rejected as required
• Package identity: 248 canonical PPDs at version 3.0.0
• GitHub merge analysis: clean, with no unresolved review threads

Physical-printer testing remains recommended before tagging the release. The legacy CUPS PPD deprecation remains documented migration debt rather than being hidden by unrelated warning suppression.

Fixes #15

[dutch2005]

ok

[dutch2005]

The rebase is complete in one branch update. GitHub reports this exact head (e2741a2) as MERGEABLE against current OpenPrinting/master, with no unresolved review threads.

Exact-head preflight is green with zero annotations: https://github.com/dutch2005/splix/actions/runs/33083553070

Maintainer note: the workflow currently present on the base branch still invokes the legacy Makefile path that this PR replaces, so it cannot validate the new CMake tree. The linked fork run executes the proposed workflow and covers ASan/UBSan plus amd64, arm64, armhf, i386, and riscv64 packages. Physical-printer testing and independent maintainer review remain the final release gates.