Minor fixes to resolve some compilation warnings

.github/workflows/ci.yml

@@ -14,12 +14,21 @@ jobs:
       matrix:
         python-version: ["3.7", "3.8", "3.9", "3.10", "3.11", "3.12", "3.13"]
         os: ["ubuntu-20.04", "macos-latest", "windows-latest"]
+        unsigned: [true, false]
 
     steps:
       - uses: actions/checkout@v3 # Pull the repository
       - uses: actions/setup-python@v4
         with:
           python-version: ${{ matrix.python-version }}
+
+      - name: Use unsigned indices
+        if: ${{ matrix.unsigned }}
+        run: |
+          cat src/annoymodule.cc | sed "s/.*\(#define ANNOYLIB_UNSIGNED_INDEX\)/\1/" > .tmp
+          cmp .tmp src/annoymodule.cc && exit 1 # ensure a change was actually made.
+          mv .tmp src/annoymodule.cc
+
       - run: pip install .
       - run: pip install h5py numpy pytest
       - run: pytest -v

setup.py

@@ -48,6 +48,7 @@
 
 if os.name != 'nt':
     extra_compile_args += ['-O3', '-ffast-math', '-fno-associative-math']
+    extra_compile_args += ['-Wall', '-Wpedantic', '-Wextra']
 
 # Add multithreaded build flag for all platforms using Python 3 and
 # for non-Windows Python 2 platforms

src/annoylib.h

@@ -408,17 +408,29 @@ struct Base {
   static inline void preprocess(void* nodes, size_t _s, const S node_count, const int f) {
     // Override this in specific metric structs below if you need to do any pre-processing
     // on the entire set of nodes passed into this index.
+
+    (void)nodes; // silence unused variable warnings.
+    (void)_s;
+    (void)node_count;
+    (void)f;
   }
 
   template<typename T, typename S, typename Node>
   static inline void postprocess(void* nodes, size_t _s, const S node_count, const int f) {
     // Override this in specific metric structs below if you need to do any post-processing
     // on the entire set of nodes passed into this index.
+
+    (void)nodes; // silence unused variable warnings.
+    (void)_s;
+    (void)node_count;
+    (void)f;
   }
 
   template<typename Node>
   static inline void zero_value(Node* dest) {
     // Initialize any fields that require sane defaults within this node.
+
+    (void)dest; // silence unused variable warnings.
   }
 
   template<typename T, typename Node>
@@ -695,6 +707,7 @@ struct DotProduct : Angular {
 
   template<typename T, typename S, typename Node>
   static inline void postprocess(void* nodes, size_t _s, const S node_count, const int f) {
+    (void)f; // silence unused variable warnings.
     for (S i = 0; i < node_count; i++) {
       Node* node = get_node_ptr<S, Node>(nodes, _s, i);
       // When an index is built, we will remember it in index item nodes to compute distances differently
@@ -743,12 +756,14 @@ struct Hamming : Base {
   }
   template<typename S, typename T>
   static inline bool margin(const Node<S, T>* n, const T* y, int f) {
+    (void)f; // silence unused variable warnings.
     static const size_t n_bits = sizeof(T) * 8;
     T chunk = n->v[0] / n_bits;
     return (y[chunk] & (static_cast<T>(1) << (n_bits - 1 - (n->v[0] % n_bits)))) != 0;
   }
   template<typename S, typename T, typename Random>
   static inline bool side(const Node<S, T>* n, const T* y, int f, Random& random) {
+    (void)random; // silence unused variable warnings.
     return margin(n, y, f);
   }
   template<typename S, typename T, typename Random>
@@ -757,6 +772,7 @@ struct Hamming : Base {
   }
   template<typename S, typename T, typename Random>
   static inline void create_split(const vector<Node<S, T>*>& nodes, int f, size_t s, Random& random, Node<S, T>* n) {
+    (void)s; // silence unused variable warnings.
     size_t cur_size = 0;
     size_t i = 0;
     int dim = f * 8 * sizeof(T);
@@ -796,6 +812,8 @@ struct Hamming : Base {
   }
   template<typename S, typename T>
   static inline void init_node(Node<S, T>* n, int f) {
+    (void)n; // silence unused variable warnings.
+    (void)f;
   }
   static const char* name() {
     return "hamming";
@@ -864,6 +882,8 @@ struct Euclidean : Minkowski {
   }
   template<typename S, typename T>
   static inline void init_node(Node<S, T>* n, int f) {
+    (void)n; // silence unused variable warnings.
+    (void)f;
   }
   static const char* name() {
     return "euclidean";
@@ -895,6 +915,8 @@ struct Manhattan : Minkowski {
   }
   template<typename S, typename T>
   static inline void init_node(Node<S, T>* n, int f) {
+    (void)n; // silence unused variable warnings.
+    (void)f;
   }
   static const char* name() {
     return "manhattan";
@@ -1202,9 +1224,10 @@ template<typename S, typename T, typename Distance, typename Random, class Threa
     // Find the roots by scanning the end of the file and taking the nodes with most descendants
     _roots.clear();
     S m = -1;
-    for (S i = _n_nodes - 1; i >= 0; i--) {
+    for (S x = _n_nodes; x > 0; x--) { // S may be unsigned, so don't use >= 0 to terminate
+      S i = x - 1;
       S k = _get(i)->n_descendants;
-      if (m == -1 || k == m) {
+      if (m == static_cast<S>(-1) || k == m) { // first condition is still valid if S is unsigned, as m would be the largest possible number of descendants
         _roots.push_back(i);
         m = k;
       } else {
@@ -1483,7 +1506,7 @@ template<typename S, typename T, typename Distance, typename Random, class Threa
     // To avoid calculating distance multiple times for any items, sort by id
     std::sort(nns.begin(), nns.end());
     vector<pair<T, S> > nns_dist;
-    S last = -1;
+    S last = -1; // Safe sentinel for unsigned S; all indices must be less than the max value of S, otherwise get_n_items() would overflow.
     for (size_t i = 0; i < nns.size(); i++) {
       S j = nns[i]; 
       if (j == last)
@@ -1508,6 +1531,7 @@ class AnnoyIndexSingleThreadedBuildPolicy {
 public:
   template<typename S, typename T, typename D, typename Random>
   static void build(AnnoyIndex<S, T, D, Random, AnnoyIndexSingleThreadedBuildPolicy>* annoy, int q, int n_threads) {
+    (void)n_threads; // silence unused variable warnings.
     AnnoyIndexSingleThreadedBuildPolicy threaded_build_policy;
     annoy->thread_build(q, 0, threaded_build_policy);
   }