try different apprach to backtracer object

include/spdlog/details/backtracer.h

@@ -13,39 +13,80 @@
 // Useful for storing debug data in case of error/warning happens.
 
 namespace spdlog {
-namespace details {
-class backtracer
-{
-    std::mutex mutex_;    
-    size_t n_messages_;
-    circular_q<log_msg_buffer> messages_;
-
-public:
-    explicit backtracer(size_t n_messages) : n_messages_{n_messages}, messages_{n_messages}
-    {}
-    
-    size_t n_messages() const
-    {
-        return n_messages_;
-    }
-   
-    void add(const log_msg &msg)
-    {
-        std::lock_guard<std::mutex> lock{mutex_};
-        messages_.push_back(log_msg_buffer{msg});
-    }
-
-    // pop all items in the q and apply the given fun on each of them.
-    void foreach_pop(std::function<void(const details::log_msg &)> fun)
-    {
-        std::lock_guard<std::mutex> lock{mutex_};
-        while (!messages_.empty())
+    namespace details {
+        class backtracer
         {
-            log_msg_buffer popped;
-            messages_.pop_front(popped);
-            fun(popped);
-        }
-    }
-};
-} // namespace details
+            mutable std::mutex mutex_;
+            std::atomic<bool> enabled_ {false};      
+            circular_q<log_msg_buffer> messages_;
+
+        public:
+            backtracer() = default;            
+            backtracer(const backtracer& other)
+            {
+                std::lock_guard<std::mutex> lock(other.mutex_);
+                enabled_ = other.enabled();
+                messages_ = other.messages_;
+            }
+
+            backtracer(backtracer&& other) SPDLOG_NOEXCEPT             
+            {
+                std::lock_guard<std::mutex> lock(other.mutex_);
+                enabled_ = other.enabled();
+                messages_ = std::move(other.messages_);
+            }
+
+            backtracer& operator=(backtracer other)
+            {
+                std::lock_guard<std::mutex> lock(mutex_);
+                enabled_ = other.enabled();
+                messages_ = other.messages_;
+                return *this;
+            }
+
+            void enable(size_t size)
+            {
+                std::lock_guard<std::mutex> lock{ mutex_ };
+                enabled_.store(true, std::memory_order_relaxed);
+                messages_ = circular_q<log_msg_buffer>{ size };
+            }
+
+
+            void disable()
+            {
+                std::lock_guard<std::mutex> lock{ mutex_ };
+                enabled_.store(false, std::memory_order_relaxed);
+            }
+
+
+            bool enabled() const
+            {
+                return enabled_.load(std::memory_order_relaxed);
+            }
+
+            operator bool() const
+            {
+                return enabled();
+            }
+
+            void push_back(const log_msg &msg)
+            {
+                std::lock_guard<std::mutex> lock{ mutex_ };
+                messages_.push_back(log_msg_buffer{ msg });
+            }
+
+            // pop all items in the q and apply the given fun on each of them.
+            void foreach_pop(std::function<void(const details::log_msg &)> fun)
+            {
+                std::lock_guard<std::mutex> lock{ mutex_ };
+                while (!messages_.empty())
+                {
+                    log_msg_buffer popped;
+                    messages_.pop_front(popped);
+                    fun(popped);
+                }
+            }
+        };
+
+    } // namespace details
 } // namespace spdlog
\ No newline at end of file

include/spdlog/details/circular_q.h

@@ -7,62 +7,101 @@
 #include <vector>
 
 namespace spdlog {
-namespace details {
-template<typename T>
-class circular_q
-{
-public:
-    using item_type = T;
-
-    explicit circular_q(size_t max_items)
-        : max_items_(max_items + 1) // one item is reserved as marker for full q
-        , v_(max_items_)
-    {}
-
-    // push back, overrun (oldest) item if no room left
-    void push_back(T &&item)
-    {
-        v_[tail_] = std::move(item);
-        tail_ = (tail_ + 1) % max_items_;
-
-        if (tail_ == head_) // overrun last item if full
+    namespace details {
+        template<typename T>
+        class circular_q
         {
-            head_ = (head_ + 1) % max_items_;
-            ++overrun_counter_;
-        }
-    }
-
-    // Pop item from front.
-    // If there are no elements in the container, the behavior is undefined.
-    void pop_front(T &popped_item)
-    {
-        popped_item = std::move(v_[head_]);
-        head_ = (head_ + 1) % max_items_;
-    }
-
-    bool empty()
-    {
-        return tail_ == head_;
-    }
-
-    bool full()
-    {
-        // head is ahead of the tail by 1
-        return ((tail_ + 1) % max_items_) == head_;
-    }
-
-    size_t overrun_counter() const
-    {
-        return overrun_counter_;
-    }
-
-private:
-    size_t max_items_;
-    typename std::vector<T>::size_type head_ = 0;
-    typename std::vector<T>::size_type tail_ = 0;
-    size_t overrun_counter_ = 0;
-    std::vector<T> v_;
-    
-};
-} // namespace details
+        public:
+            using item_type = T;
+
+            // empty cir
+            circular_q() = default;
+
+            explicit circular_q(size_t max_items)
+                : max_items_(max_items + 1) // one item is reserved as marker for full q
+                , v_(max_items_)
+            {}
+
+
+
+            circular_q(const circular_q&) = default;
+            circular_q& operator=(const circular_q&) = default;
+
+            // move cannot be default,
+            // since we need to reset head_, tail_, etc to zero in the moved object
+            circular_q(circular_q&& other) SPDLOG_NOEXCEPT:
+            {
+                copy_moveable(std::move(other));
+            }
+
+            circular_q& operator=(circular_q&& other) SPDLOG_NOEXCEPT
+            {
+                copy_moveable(std::move(other));
+                return *this;
+            }
+
+
+            // push back, overrun (oldest) item if no room left
+            void push_back(T &&item)
+            {               
+                if(max_items_ > 0)
+                {
+                    v_[tail_] = std::move(item);
+                    tail_ = (tail_ + 1) % max_items_;
+
+                    if (tail_ == head_) // overrun last item if full
+                    {
+                        head_ = (head_ + 1) % max_items_;
+                        ++overrun_counter_;
+                    }
+                }
+            }
+
+            // Pop item from front.
+            // If there are no elements in the container, the behavior is undefined.
+            void pop_front(T &popped_item)
+            {
+                if(max_items_ > 0)
+                {
+                    popped_item = std::move(v_[head_]);
+                    head_ = (head_ + 1) % max_items_;
+                }
+            }
+
+            bool empty()
+            {
+                return tail_ == head_;
+            }
+
+            bool full()
+            {
+                // head is ahead of the tail by 1
+                return ((tail_ + 1) % max_items_) == head_;
+            }
+
+            size_t overrun_counter() const
+            {
+                return overrun_counter_;
+            }
+
+        private:
+            size_t max_items_ = 0;
+            typename std::vector<T>::size_type head_ = 0;
+            typename std::vector<T>::size_type tail_ = 0;
+            size_t overrun_counter_ = 0;
+            std::vector<T> v_;
+
+
+            void copy_moveable(circular_q&& other) SPDLOG_NOEXCEPT
+            {
+                max_items_ = other.max_items_;
+                head_ = other.head_;
+                tail_ = other.tail_;
+                overrun_counter_ = other.overrun_counter_,
+                v_ = std::move(other.v_);                
+                other.max_items_ = 0; // disable other                                
+            }
+
+        };
+    } // namespace details
 } // namespace spdlog

include/spdlog/details/log_msg_buffer.h

@@ -47,6 +47,14 @@ public:
         update_string_views();
     }
 
+    log_msg_buffer &operator=(log_msg_buffer &other)
+    {
+        log_msg::operator=(other);
+        buffer.append(other.buffer.begin(), other.buffer.end());
+        update_string_views();
+        return *this;
+    }
+
     log_msg_buffer &operator=(log_msg_buffer &&other)
     {
         log_msg::operator=(std::move(other));

include/spdlog/logger-inl.h

@@ -23,11 +23,7 @@ SPDLOG_INLINE logger::logger(const logger &other)
     , flush_level_(other.flush_level_.load(std::memory_order_relaxed))
     , custom_err_handler_(other.custom_err_handler_)
     , tracer_(other.tracer_)
-{
-    if (tracer_)
-    {
-        enable_backtrace(tracer_->n_messages());
-    }
+{    
 }
 
 SPDLOG_INLINE logger::logger(logger &&other) SPDLOG_NOEXCEPT : name_(std::move(other.name_)),
@@ -61,7 +57,7 @@ SPDLOG_INLINE void logger::swap(spdlog::logger &other) SPDLOG_NOEXCEPT
     other.flush_level_.store(tmp);
 
     custom_err_handler_.swap(other.custom_err_handler_);
-    tracer_.swap(other.tracer_);
+    std::swap(tracer_, other.tracer_);    
 }
 
 SPDLOG_INLINE void swap(logger &a, logger &b)
@@ -116,13 +112,13 @@ SPDLOG_INLINE void logger::set_pattern(std::string pattern, pattern_time_type ti
 // create new backtrace sink and move to it all our child sinks
 SPDLOG_INLINE void logger::enable_backtrace(size_t n_messages)
 {
-    tracer_ = std::make_shared<details::backtracer>(n_messages);
+    tracer_.enable(n_messages);
 }
 
 // restore orig sinks and level and delete the backtrace sink
 SPDLOG_INLINE void logger::disable_backtrace()
 {
-    tracer_.reset();
+    tracer_.disable();
 }
 
 SPDLOG_INLINE void logger::dump_backtrace()
@@ -206,7 +202,7 @@ SPDLOG_INLINE void logger::flush_()
 
 SPDLOG_INLINE void logger::backtrace_add_(const details::log_msg &msg)
 {
-    tracer_->add(msg);
+    tracer_.push_back(msg);
 }
 
 SPDLOG_INLINE void logger::dump_backtrace_()
@@ -215,7 +211,7 @@ SPDLOG_INLINE void logger::dump_backtrace_()
     if (tracer_)
     {
         sink_it_(log_msg{name(), level::info, "****************** Backtrace Start ******************"});
-        tracer_->foreach_pop([this](const details::log_msg &msg) { this->sink_it_(msg); });
+        tracer_.foreach_pop([this](const details::log_msg &msg) { this->sink_it_(msg); });
         sink_it_(log_msg{name(), level::info, "****************** Backtrace End ********************"});
     }
 }

include/spdlog/logger.h

@@ -17,6 +17,7 @@
 
 #include "spdlog/common.h"
 #include "spdlog/details/log_msg.h"
+#include "spdlog/details/backtracer.h"
 
 #ifdef SPDLOG_WCHAR_TO_UTF8_SUPPORT
 #include "spdlog/details/os.h"
@@ -39,10 +40,6 @@
 
 namespace spdlog {
 
-namespace details {
-class backtracer;
-}
-
 class logger
 {
 public:
@@ -365,7 +362,7 @@ protected:
     spdlog::level_t level_{level::info};
     spdlog::level_t flush_level_{level::off};
     err_handler custom_err_handler_{nullptr};
-    std::shared_ptr<details::backtracer> tracer_;
+    details::backtracer tracer_;
 
     virtual void sink_it_(const details::log_msg &msg);
     virtual void flush_();