Avoid un necessary move when popping circular_q

include/spdlog/details/backtracer-inl.h

@@ -65,9 +65,9 @@ SPDLOG_INLINE void backtracer::foreach_pop(std::function<void(const details::log
     std::lock_guard<std::mutex> lock{mutex_};
     while (!messages_.empty())
     {
-        log_msg_buffer popped;
+        auto &front_msg = messages_.front();
-        messages_.pop_front(popped);
+        messages_.pop_front();
-        fun(popped);
+        fun(front_msg);
     }
 }
 } // namespace details

include/spdlog/details/circular_q.h

@@ -60,16 +60,19 @@ public:
         }
     }
 
+    // Return reference to the front item.
+    // If there are no elements in the container, the behavior is undefined.
+    T& front()
+    {
+        return v_[head_];
+    }
+
     // Pop item from front.
     // If there are no elements in the container, the behavior is undefined.
-    void pop_front(T &popped_item)
+    void pop_front()
     {
-        if (max_items_ > 0)
-        {
-            popped_item = std::move(v_[head_]);
         head_ = (head_ + 1) % max_items_;
     }
-    }
 
     bool empty() const
     {
@@ -79,8 +82,12 @@ public:
     bool full() const
     {
         // head is ahead of the tail by 1
+        if(max_items_ > 0)
+        {
             return ((tail_ + 1) % max_items_) == head_;
         }
+        return true;
+    }
 
     size_t overrun_counter() const
     {

include/spdlog/details/mpmc_blocking_q.h

@@ -59,7 +59,8 @@ public:
             {
                 return false;
             }
-            q_.pop_front(popped_item);
+            popped_item = std::move(q_.front());
+            q_.pop_front();
         }
         pop_cv_.notify_one();
         return true;

include/spdlog/sinks/daily_file_sink.h

@@ -139,8 +139,8 @@ private:
         filename_t current_file = filename();
         if (filenames_q_.full())
         {
-            filename_t old_filename;
+            auto &old_filename = filenames_q_.front();
-            filenames_q_.pop_front(old_filename);
+            filenames_q_.pop_front();
             bool ok = remove_if_exists(old_filename) == 0;
             if (!ok)
             {