Meta: hardening pass - exception safety, container correctness, and object-model safety

[Dikluwe]

Purpose

This issue is the coordination index for the current hardening work. At the time of creation there are 11 draft pull requests, several of them stacked or touching the same legacy containers and path implementation files.

Detailed design and review discussion should remain in each pull request. This issue should only track dependency order, readiness, and merge progress.

Working rules

• Keep dependent PRs as drafts until every prerequisite is merged.
• After a prerequisite merges, refresh the direct child from master, rerun its focused validation, and only then mark it ready for review.
• Review overlapping SoPath changes sequentially even when they are logically independent.
• Update this checklist after each merge instead of opening coordination comments across every PR.

Dependency map

SbHash:
#750 -> #751 -> #752 -> #753 -> #754 -> #755

SbList / SbSmallMap / GL:
#756 -> #757 -> #758 --\
#755 -------------------> #760
#759 ------------------/

SbHash stack

• Fix SbHash self-assignment #750 - self-assignment fix; non-draft stack root
• Fix SbHash mutable iterator traversal #751 - mutable iterator traversal; draft, waits for Fix SbHash self-assignment #750
• Fix SbHash statistics calculation #752 - statistics; draft, waits for Fix SbHash mutable iterator traversal #751
• Define the SbHash noexcept hash contract #753 - non-throwing hash contract; draft, waits for Fix SbHash statistics calculation #752
• Relink SbHash entries during resize #754 - relink during resize; draft, waits for Define the SbHash noexcept hash contract #753
• Defer SbHash storage allocation #755 - lazy storage; draft, waits for Relink SbHash entries during resize #754

SbList, SbSmallMap, and GL-context stack

• Make SbList growth exception safe #756 - SbList growth and fit exception safety; non-draft, review fixes pushed and awaiting re-review
• Add SbSmallMap for the profiler texture cache #757 - profiler texture SbSmallMap; draft, waits for Make SbList growth exception safe #756
• Use SbSmallMap for small GL context caches #758 - small GL-context caches; draft, waits for Add SbSmallMap for the profiler texture cache #757
• Fix SoShape bump programs across GL cache contexts #759 - bump-program context lifecycle; independent non-draft prerequisite for Use SbSmallMap for active bump program contexts #760
• Use SbSmallMap for active bump program contexts #760 - active bump-program SbSmallMap; draft, waits for Defer SbHash storage allocation #755, Use SbSmallMap for small GL context caches #758, and Fix SoShape bump programs across GL cache contexts #759
• Make SbPList growth exception safe #740 - related but independent SbPList growth exception safety

SoPath and object-model hardening

These fixes are mostly independent in intent but overlap in SoPath and related implementation files. Proposed coordination is to land #714 first, then refresh and review the remaining PRs sequentially from master.

• Fix SoPath/SoFullPath downcast undefined behavior across the codebase #714 - safe full-path view and removal of invalid SoPath to SoFullPath downcasts
• Validate SoPath child appends in all builds #742 - validate child appends
• Validate legacy SoPath accessor bounds in all builds #743 - validate legacy accessor bounds
• Harden SoPath range and stack operations in all builds #744 - harden range and stack operations
• Guard SoTempPath::replaceTail() on empty paths #745 - guard empty SoTempPath::replaceTail()
• Preserve SoTempPath policy when appending to empty paths #746 - preserve SoTempPath policy when appending to an empty path
• Restore safe SoNodeKitPath object semantics #747 - restore safe SoNodeKitPath object semantics
• Fix SoPath assignment auditor lifecycle #748 - assignment auditor lifecycle; draft
• Validate SoPath auditor callbacks in all builds #749 - auditor callback validation; draft

Recently resolved prerequisites

• Use SbString for SoInput numeric parsing buffer #736 - SoInput_FileInfo buffer migrated to SbString; merged, and Clear the SoInput real-number parsing buffer #737 was refreshed from master
• Fix SbList removal of missing items #738 - missing-item removal in SbList; merged, and Make SbList growth exception safe #756 was refreshed from master

Independent hardening PRs

• Fix -Wundef debug-diagnostic bugs in SoField and SoVRMLGroup #677 - debug diagnostic configuration
• Harden SbHeap edge-case handling #724 - SbHeap edge cases
• Fix cc_heap arbitrary removal and duplicate handling #725 - cc_heap arbitrary removal and duplicates
• Harden cc_dict resizing and hash changes #726 - cc_dict resize and hash changes
• Clear the SoInput real-number parsing buffer #737 - clear the real-number parsing buffer
• Restore CoinTests run_test filtering #739 - restore CoinTests command-line filtering
• Add robust three-plane intersection #761 - robust three-plane intersection; standalone draft with no merged parent identified

Next promotions

• When Fix SbHash self-assignment #750 merges: refresh Fix SbHash mutable iterator traversal #751 from master, validate it, and mark it ready.
• When Make SbList growth exception safe #756 merges: refresh Add SbSmallMap for the profiler texture cache #757 from master, validate it, and mark it ready.
• Continue one direct child at a time; do not promote the full stacks together.