Replaced backtace implementation

include/spdlog/details/backtracer.h

@@ -0,0 +1,45 @@
+// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
+// Distributed under the MIT License (http://opensource.org/licenses/MIT)
+
+#pragma once
+
+#include "spdlog/common.h"
+#include "spdlog/details/log_msg_buffer.h"
+#include "spdlog/details/circular_q.h"
+#include "spdlog/sinks/sink.h"
+#include <mutex>
+
+// Store log messages in circular buffer.
+// Useful for storing debug data in case of error/warning happens.
+
+namespace spdlog {
+namespace details {
+class backtracer
+{
+    std::mutex mutex_;
+    circular_q<log_msg_buffer> messages_;
+
+public:
+    explicit backtracer(size_t n_message)
+        : messages_{n_message}
+    {}
+
+    void add_msg(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 give fun on each of them.
+    void foreach_pop(std::function<void(const details::log_msg)> fun)
+    {
+        while (!messages_.empty())
+        {
+            log_msg_buffer popped;
+            messages_.pop_front(popped);
+            fun(popped);
+        }
+    }
+};
+} // namespace details
+} // namespace spdlog