Logging: Fix fmt errors after rebasing with master

fmt was updated during the clang-format update, which breaks the previous implementation of FmtLogMessage

Changes were:
* Move definition of FmtLogMessage into log.h to use variadic templates as FMT_VARIADIC was removed

To supplement the change above:
* Move Entry and CreateEntry into log.h
* Add LogEntry in backend.cpp

src/common/logging/backend.cpp

@@ -265,15 +265,11 @@ void LogMessage(Class log_class, Level log_level, const char* filename, unsigned
     Impl::Instance().PushEntry(std::move(entry));
 }
 
-void FmtLogMessage(Class log_class, Level log_level, const char* filename, unsigned int line_num,
-                   const char* function, const char* format, fmt::ArgList args) {
+void LogEntry(Entry& entry) {
     auto filter = Impl::Instance().GetGlobalFilter();
-    if (!filter.CheckMessage(log_class, log_level))
+    if (!filter.CheckMessage(entry.log_class, entry.log_level))
         return;
 
-    Entry entry =
-        CreateEntry(log_class, log_level, filename, line_num, function, fmt::format(format, args));
-
     Impl::Instance().PushEntry(std::move(entry));
 }
 } // namespace Log

src/common/logging/backend.h

@@ -18,26 +18,6 @@ namespace Log {
 
 class Filter;
 
-/**
- * A log entry. Log entries are store in a structured format to permit more varied output
- * formatting on different frontends, as well as facilitating filtering and aggregation.
- */
-struct Entry {
-    std::chrono::microseconds timestamp;
-    Class log_class;
-    Level log_level;
-    std::string filename;
-    unsigned int line_num;
-    std::string function;
-    std::string message;
-
-    Entry() = default;
-    Entry(Entry&& o) = default;
-
-    Entry& operator=(Entry&& o) = default;
-    Entry& operator=(const Entry& o) = default;
-};
-
 /**
  * Interface for logging backends. As loggers can be created and removed at runtime, this can be
  * used by a frontend for adding a custom logging backend as needed
@@ -112,10 +92,6 @@ const char* GetLogClassName(Class log_class);
  */
 const char* GetLevelName(Level log_level);
 
-/// Creates a log entry by formatting the given source location, and message.
-Entry CreateEntry(Class log_class, Level log_level, const char* filename, unsigned int line_nr,
-                  const char* function, std::string message);
-
 /**
  * The global filter will prevent any messages from even being processed if they are filtered. Each
  * backend can have a filter, but if the level is lower than the global filter, the backend will

src/common/logging/log.h

@@ -4,6 +4,7 @@
 
 #pragma once
 
+#include <chrono>
 #include <fmt/format.h>
 #include "common/common_types.h"
 
@@ -98,6 +99,33 @@ enum class Class : ClassType {
     Count              ///< Total number of logging classes
 };
 
+/**
+ * A log entry. Log entries are store in a structured format to permit more varied output
+ * formatting on different frontends, as well as facilitating filtering and aggregation.
+ */
+struct Entry {
+    std::chrono::microseconds timestamp;
+    Class log_class;
+    Level log_level;
+    std::string filename;
+    unsigned int line_num;
+    std::string function;
+    std::string message;
+
+    Entry() = default;
+    Entry(Entry&& o) = default;
+
+    Entry& operator=(Entry&& o) = default;
+    Entry& operator=(const Entry& o) = default;
+};
+
+/// Creates a log entry by formatting the given source location, and message.
+Entry CreateEntry(Class log_class, Level log_level, const char* filename, unsigned int line_nr,
+                  const char* function, std::string message);
+
+// Logs an Entry
+void LogEntry(Entry& entry);
+
 /// Logs a message to the global logger.
 void LogMessage(Class log_class, Level log_level, const char* filename, unsigned int line_num,
                 const char* function,
@@ -112,10 +140,14 @@ void LogMessage(Class log_class, Level log_level, const char* filename, unsigned
     ;
 
 /// Logs a message to the global logger, this time with 100% moar fmtlib
+template <typename... Args>
 void FmtLogMessage(Class log_class, Level log_level, const char* filename, unsigned int line_num,
-                   const char* function, const char* format, fmt::ArgList);
+                   const char* function, const char* format, const Args & ... args) {
+    Entry entry =
+        CreateEntry(log_class, log_level, filename, line_num, function, fmt::format(format, args...));
 
-FMT_VARIADIC(void, FmtLogMessage, Class, Level, const char*, unsigned int, const char*, const char*)
+    LogEntry(entry);
+}
 
 } // namespace Log