feat: add wait_for_tasks() (#62)

Added `wait_for_tasks()` feature, building on top of the work done in #61. This simply refactors some of that code into a public method that users can call to block the current thread and wait for all tasks to complete.

.github/workflows/style.yml

@@ -25,7 +25,7 @@ jobs:
 
       - name: Install format dependencies
         run: |
-          choco install llvm --version 16.0.1 -y
+          choco install llvm --version 18.1.3 -y
           choco install ninja -y
           pip3 install cmake_format==0.6.11 pyyaml
 

include/thread_pool/thread_pool.h

@@ -98,10 +98,7 @@ namespace dp {
         }
 
         ~thread_pool() {
-            if (completed_tasks_.load(std::memory_order_acquire) > 0) {
-                // wait for all tasks to finish
-                threads_done_.acquire();
-            }
+            wait_for_tasks();
 
             // stop all threads
             for (std::size_t i = 0; i < threads_.size(); ++i) {
@@ -207,6 +204,13 @@ namespace dp {
 
         [[nodiscard]] auto size() const { return threads_.size(); }
 
+        void wait_for_tasks() {
+            if (completed_tasks_.load(std::memory_order_acquire) > 0) {
+                // wait for all tasks to finish
+                threads_done_.acquire();
+            }
+        }
+
       private:
         template <typename Function>
         void enqueue_task(Function &&f) {

test/source/thread_pool.cpp

@@ -423,3 +423,25 @@ TEST_CASE("Test premature exit") {
     CHECK_NE(spawn_task_id, task_3_id);
     CHECK_NE(task_1_id, task_2_id);
 }
+
+TEST_CASE("Ensure wait_for_tasks() properly blocks current execution.") {
+    std::atomic counter = 0;
+    int total_tasks{};
+    constexpr auto thread_count = 4;
+
+    SUBCASE("with tasks") { total_tasks = 30; }
+    SUBCASE("with no tasks") { total_tasks = 0; }
+    SUBCASE("with task count less than thread count") { total_tasks = thread_count / 2; }
+
+    dp::thread_pool pool(thread_count);
+    for (auto i = 0; i < total_tasks; i++) {
+        auto task = [i, &counter]() {
+            std::this_thread::sleep_for(std::chrono::milliseconds((i + 1) * 10));
+            ++counter;
+        };
+        pool.enqueue_detach(task);
+    }
+    pool.wait_for_tasks();
+
+    CHECK_EQ(counter.load(), total_tasks);
+}