From cbfed38778dc4b854517541e986e0017d49871d8 Mon Sep 17 00:00:00 2001
From: Martin Pluskal <martin@pluskal.org>
Date: Thu, 30 Jul 2026 14:46:55 +0200
Subject: [PATCH] Guard the SVS code paths so USE_SVS=OFF builds

Building with -DUSE_SVS=OFF does not compile. HAVE_SVS is then 0 and the
ScalableVectorSearch sources are never fetched, but two translation units still
reach for SVS unconditionally:

  src/VecSim/algorithms/svs/svs.h:21:10: fatal error:
      svs/index/vamana/dynamic_index.h: No such file or directory
    (via tiered_factory.h -> svs_tiered.h -> svs.h)

  src/VecSim/algorithms/svs/svs_utils.h:16:10: fatal error:
      svs/core/distance.h: No such file or directory
    (via vec_sim.cpp)

tiered_factory.h needs nothing from svs_tiered.h -- none of its declarations
mention an SVS type -- so that include is simply guarded, the way
tiered_factory.cpp and svs_factory.cpp already guard the same headers.

vec_sim.cpp does use VecSimSVSThreadPool, in two functions that are part of the
public C API and so have to keep existing either way:

  - VecSim_UpdateThreadPoolSize() sets the write mode and then resizes the
    shared SVS pool. With no SVS there is no pool, and setting the write mode is
    all the call has to do.
  - VecSim_GetSharedMemory() reports the process-wide shared allocation. That is
    an SVS construct; without it nothing is held outside the individual indexes,
    which already report their own, so it returns 0.
---
 src/VecSim/index_factories/tiered_factory.h |  2 ++
 src/VecSim/vec_sim.cpp                      | 14 ++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/src/VecSim/index_factories/tiered_factory.h b/src/VecSim/index_factories/tiered_factory.h
index fbb55d3b3..3cf0d5db5 100644
--- a/src/VecSim/index_factories/tiered_factory.h
+++ b/src/VecSim/index_factories/tiered_factory.h
@@ -13,7 +13,9 @@
 #include "VecSim/memory/vecsim_malloc.h"
 #include "VecSim/vec_sim_index.h"
 #include "VecSim/algorithms/hnsw/hnsw_tiered.h"
+#if HAVE_SVS
 #include "VecSim/algorithms/svs/svs_tiered.h"
+#endif
 #include "VecSim/algorithms/brute_force/brute_force.h"
 #include "VecSim/index_factories/factory_utils.h"
 
diff --git a/src/VecSim/vec_sim.cpp b/src/VecSim/vec_sim.cpp
index 4fed53ab8..9da4eb392 100644
--- a/src/VecSim/vec_sim.cpp
+++ b/src/VecSim/vec_sim.cpp
@@ -15,7 +15,9 @@
 #include "VecSim/vec_sim_index.h"
 #include "VecSim/vec_sim_adhoc_bf_ctx.h"
 #include "VecSim/types/bfloat16.h"
+#if HAVE_SVS
 #include "VecSim/algorithms/svs/svs_utils.h"
+#endif
 #include <cassert>
 #include "memory.h"
 
@@ -41,10 +43,16 @@ extern "C" void VecSim_UpdateThreadPoolSize(size_t new_size) {
     } else {
         VecSimIndex::setWriteMode(VecSim_WriteAsync);
     }
+#if HAVE_SVS
     // Resize the shared SVS pool. Clamped to a minimum of 1. OS threads are spawned
     // lazily on first SVS index creation; once an index exists this resizes the
     // shared pool immediately (cooperating with the deferred-shrink protocol).
     VecSimSVSThreadPool::resize(new_size);
+#else
+    // No SVS, so there is no shared pool to resize; the write mode set above is
+    // all this call has to do.
+    (void)new_size;
+#endif
 }
 
 static VecSimResolveCode _ResolveParams_EFRuntime(VecSimAlgo index_type, VecSimRawParam rparam,
@@ -392,7 +400,13 @@ extern "C" VecSimDebugInfoIterator *VecSimIndex_DebugInfoIterator(VecSimIndex *i
 }
 
 extern "C" size_t VecSim_GetSharedMemory(void) {
+#if HAVE_SVS
     return VecSimSVSThreadPool::getSharedAllocationSize();
+#else
+    // The shared pool is an SVS construct; without it no memory is held outside
+    // the individual indexes, which already report their own.
+    return 0;
+#endif
 }
 
 extern "C" VecSimIndexBasicInfo VecSimIndex_BasicInfo(VecSimIndex *index) {