fix(search-buffer): ASan heap-buffer-underflow in SearchBuffer::can_skip (#241)

ahuber21 · web-flow · commit e39360a1a8cb · 2025-12-11T10:53:25.000+01:00
ASan will be added in #239. It flags `SearchBuffer::can_skip`. Here we reorder the logic to check `full()` before accessing `back()`. Accessing `back()` on an empty buffer caused an index underflow (`SIZE_MAX`).
diff --git a/include/svs/index/vamana/search_buffer.h b/include/svs/index/vamana/search_buffer.h
@@ -340,7 +340,7 @@ template <typename Idx, typename Cmp = std::less<>> class SearchBuffer {
     /// returns ``true``.
     ///
     bool can_skip(float distance) const {
-        return compare_(back().distance(), distance) && full();
+        return full() && (capacity() == 0 || compare_(back().distance(), distance));
     }
 
     ///

Original file line number	Diff line number	Diff line change
`@@ -340,7 +340,7 @@ template <typename Idx, typename Cmp = std::less<>> class SearchBuffer {`
`340`	`340`	/// returns ``true``.
`341`	`341`	`///`
`342`	`342`	`bool can_skip(float distance) const {`
`343`		`- return compare_(back().distance(), distance) && full();`
	`343`	`+ return full() && (capacity() == 0 \|\| compare_(back().distance(), distance));`
`344`	`344`	`}`
`345`	`345`
`346`	`346`	`///`