MOD-15579 Report 0 shared SVS memory until first index attaches

src/VecSim/algorithms/svs/svs_utils.h

@@ -462,15 +462,25 @@ class VecSimSVSThreadPoolImpl {
     // outside of the pool, nor per-index wrapper state.
     size_t getAllocationSize() const { return allocator_->getAllocationSize(); }
 
-    // Bytes allocated by the shared pool singleton. Returns 0 if the singleton has
-    // never been constructed (e.g., no SVS index was ever created and
-    // VecSim_UpdateThreadPoolSize was never called). Safe to call from any context;
-    // does not force singleton construction.
+    // Bytes allocated by the shared pool singleton. Returns 0 until the first SVS index
+    // attaches, for either reason:
+    //   * the singleton was never constructed (no SVS index created and
+    //     VecSim_UpdateThreadPoolSize never called), or
+    //   * it was constructed to record a requested size (VecSim_UpdateThreadPoolSize at
+    //     module init) but no SVS index has attached yet.
+    // This keeps process-wide vector memory reported as 0 on deployments that only use
+    // non-SVS indexes (or none at all). Safe to call from any context; does not force
+    // singleton construction.
     static size_t getSharedAllocationSize() {
         if (!isInitialized()) {
             return 0;
         }
-        return instance()->getAllocationSize();
+        auto pool = instance();
+        std::lock_guard lock{pool->pool_mutex_};
+        if (!pool->has_attached_index_) {
+            return 0;
+        }
+        return pool->getAllocationSize();
     }
 
     // Resize the shared pool. in all cases the requested size is stored in

tests/unit/test_svs.cpp

@@ -3445,12 +3445,13 @@ TYPED_TEST(SVSTest, sharedMemoryTracksThreadPoolResize) {
 // ---------------------------------------------------------------------------
 TEST(SVSTest, ThreadPoolLazyInit) {
     // Reset the shared singleton to a clean state — earlier tests may have
-    // attached indexes and resized the pool. After reset, getAllocationSize()
-    // still reports sizeof(VecSimAllocator) (the allocator's self-accounting,
-    // see VecSimAllocator() ctor); assertions below compare against this
-    // baseline rather than absolute zero.
+    // attached indexes and resized the pool. resetForTest() clears
+    // has_attached_index_, so VecSim_GetSharedMemory() reports 0 even though the
+    // singleton object (and its self-accounting allocator) still exist: shared
+    // memory is only attributed once an SVS index attaches.
     VecSimSVSThreadPoolImpl::instance()->resetForTest();
     const size_t baseline_mem = VecSim_GetSharedMemory();
+    EXPECT_EQ(baseline_mem, 0u) << "shared memory must be 0 before any SVS index attaches";
 
     // Recording a non-trivial requested size before any SVS index exists must
     // not allocate any worker slots.