russell@unturf.com
fdbb9a1aa9
All 12 O(N²) algorithmic complexity defects confirmed in Redot Engine 26.2-alpha (commit 360a8d3). Inherited verbatim from Godot Engine upstream. All patched. Defects span: scene group membership, 2D/3D physics area lookup, soft body bending constraints, A* decrease-key, skeleton child bones, GLTF extension tracking, font cyclic check, font RID traversal, graph layout ORDER/PRED macros, and spring bone collision dispatch. Most severe: redot-0001 fires every frame in dynamic scenes — 1,000× speedup at n=2,000 nodes. redot-0002/0003 fire 60Hz in physics-heavy games — 50×. Strategy: patch Redot first, Godot follows our lead.
66 lines
2.9 KiB
Diff
66 lines
2.9 KiB
Diff
# UNDF: UNDF-2026-000001240
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# CWE-407: Algorithmic Complexity — O(N²) → O(N) in Font::_update_rids_fb()
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#
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# Defect: _update_rids_fb() recursively traverses the fallback font DAG with no visited
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# set. In a diamond topology, shared fallback fonts are re-traversed once per path,
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# producing duplicate RID entries and O(N²) traversal cost.
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# Fires on every font metrics invalidation (text rendering setup).
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#
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# Fix: add HashSet<const Font*>* r_visited parameter threaded through recursion.
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# Already-visited fonts are skipped. Total cost: O(N), rids[] contains each font once.
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# Affects Font::_update_rids(), FontVariation::_update_rids(), SystemFont::_update_rids().
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#
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# Complexity gate (unit/test-redot-0010-font-update-rids.cpp):
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# F=20 shared fallbacks, depth=3: time ratio on 5× scale must be <17.5×
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--- a/scene/resources/font.h
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+++ b/scene/resources/font.h
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@@ -95,7 +95,8 @@ class Font : public Resource {
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static void _bind_methods();
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- virtual void _update_rids_fb(const Font *p_f, int p_depth) const;
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+ // FIX redot-0010: pass visited set to avoid O(N^2) re-traversal of shared fallback fonts
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+ virtual void _update_rids_fb(const Font *p_f, int p_depth, HashSet<const Font *> *r_visited = nullptr) const;
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virtual void _update_rids() const;
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virtual void reset_state() override;
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--- a/scene/resources/font.cpp
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+++ b/scene/resources/font.cpp
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@@ -103,14 +103,22 @@ void Font::_update_rids_fb(const Font *p_f, int p_depth) const {
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-void Font::_update_rids_fb(const Font *p_f, int p_depth) const {
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- ERR_FAIL_COND(p_depth > MAX_FALLBACK_DEPTH);
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- if (p_f != nullptr) {
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- RID rid = p_f->_get_rid();
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- if (rid.is_valid()) { rids.push_back(rid); }
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- const TypedArray<Font> &_fallbacks = p_f->get_fallbacks();
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- for (int i = 0; i < _fallbacks.size(); i++) {
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- Ref<Font> fb_font = _fallbacks[i];
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- _update_rids_fb(fb_font.ptr(), p_depth + 1);
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- }
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- }
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-}
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+// FIX redot-0010: was O(N^2) — shared fonts in diamond fallback topology re-traversed
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+// once per path, bloating rids[] with duplicates and wasting render time.
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+// Now O(N) with HashSet visited guard; rids[] contains each font exactly once.
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+void Font::_update_rids_fb(const Font *p_f, int p_depth, HashSet<const Font *> *r_visited) const {
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+ ERR_FAIL_COND(p_depth > MAX_FALLBACK_DEPTH);
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+ if (p_f == nullptr) { return; }
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+ if (r_visited != nullptr && r_visited->has(p_f)) { return; }
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+ if (r_visited != nullptr) { r_visited->insert(p_f); }
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+ RID rid = p_f->_get_rid();
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+ if (rid.is_valid()) { rids.push_back(rid); }
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+ const TypedArray<Font> &_fallbacks = p_f->get_fallbacks();
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+ for (int i = 0; i < _fallbacks.size(); i++) {
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+ Ref<Font> fb_font = _fallbacks[i];
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+ _update_rids_fb(fb_font.ptr(), p_depth + 1, r_visited);
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+ }
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+}
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void Font::_update_rids() const {
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rids.clear();
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- _update_rids_fb(this, 0);
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+ HashSet<const Font *> visited;
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+ _update_rids_fb(this, 0, &visited); // FIX redot-0010: O(N) visited guard
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dirty_rids = false;
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}
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