`range_search()` crashes with `narrowing_error` when a query returns >= 65,536 results

[izaakk]

Summary

range_search() on any DynamicVamanaIndex crashes when a single query returns >= 65,536 results (2^16). The runtime internally narrows the per-query result count to uint16_t, which overflows and throws svs::lib::narrowing_error. Because range_search() is noexcept, this calls std::terminate().

All storage kinds are affected (FP32, FP16, LVQ, LeanVec) — the bug is in the core range search path inside libsvs_runtime.so.

Version: v0.1.0 (svs-cpp-runtime-bindings-0.1.0.tar.gz)

Steps to Reproduce

Generate 100K random 768D vectors, build a DynamicVamanaIndex, and run range_search with a radius large enough to match >65K vectors:

#include <svs/runtime/dynamic_vamana_index.h>
// ... build index with 100,000 vectors (768D, L2) ...
// range_search with radius=550 -> ~98K vectors match -> CRASH

A full standalone reproducer (FAISS-based, ~150 lines) is attached

d_reproduce_range_search_crash.cpp

Crash output:

terminate called after throwing an instance of 'svs::lib::narrowing_error'
  what():  narrowing_error
Aborted (core dumped)

Evidence: Crash Threshold Is Exactly 2^16

Search over radius values with 100K random vectors (768D, L2, FP32):

Radius	Result Count	Status
519.30	65,209	OK
519.35	>= 65,536	CRASH

The boundary is exactly 65,536 = UINT16_MAX + 1. Below this threshold, all queries succeed. At or above, every query crashes.

FAISS's own IndexFlatL2 and IndexHNSW handle the same data and radius correctly, returning >65K results without issue.

Expected Behavior

range_search() should handle any result count. The internal per-query result counter should use size_t (or at minimum uint32_t) instead of uint16_t.

Environment

• Ubuntu 24.04, GCC 13.3.0, C++20
• AWS r8i.4xlarge
• Also reproduced via OpenSearch 3.4.0 with FAISS SVS integration (manifests as SIGSEGV in libsvs_runtime.so+0x2b69a2)