From 001675dced1b7b751d1db4f0d6490776c613df2f Mon Sep 17 00:00:00 2001
From: yzct12345 <87620833+yzct12345@users.noreply.github.com>
Date: Fri, 13 Aug 2021 18:39:45 +0000
Subject: logging: Simplify and make thread-safe

This simplifies the logging system.

This also fixes some lost messages on startup.

The simplification is simple. I removed unused functions and moved most things in the .h to the .cpp. I replaced the unnecessary linked list with its contents laid out as three member variables. Anything that went through the linked list now directly accesses the backends. Generic functions are replaced with those for each specific use case and there aren't many. This change increases coupling but we gain back more KISS and encapsulation.

With those changes it was easy to make it thread-safe. I just removed the mutex and turned a boolean atomic. I was planning to use this thread-safety in my next PR about stacktraces. It was actually async-signal-safety at first but I ended up using a different approach. Anyway getting rid of the linked list is important for that because have the list of backends constantly changing complicates things.
---
 src/common/logging/backend.h | 113 +++----------------------------------------
 1 file changed, 7 insertions(+), 106 deletions(-)

(limited to 'src/common/logging/backend.h')

diff --git a/src/common/logging/backend.h b/src/common/logging/backend.h
index 4b9a910c1..cb7839ee9 100644
--- a/src/common/logging/backend.h
+++ b/src/common/logging/backend.h
@@ -5,120 +5,21 @@
 #pragma once
 
 #include <filesystem>
-#include <memory>
-#include <string>
-#include <string_view>
 #include "common/logging/filter.h"
-#include "common/logging/log.h"
-
-namespace Common::FS {
-class IOFile;
-}
 
 namespace Common::Log {
 
 class Filter;
 
-/**
- * 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
- */
-class Backend {
-public:
-    virtual ~Backend() = default;
-
-    virtual void SetFilter(const Filter& new_filter) {
-        filter = new_filter;
-    }
-    virtual const char* GetName() const = 0;
-    virtual void Write(const Entry& entry) = 0;
-
-private:
-    Filter filter;
-};
-
-/**
- * Backend that writes to stderr without any color commands
- */
-class ConsoleBackend : public Backend {
-public:
-    ~ConsoleBackend() override;
-
-    static const char* Name() {
-        return "console";
-    }
-    const char* GetName() const override {
-        return Name();
-    }
-    void Write(const Entry& entry) override;
-};
-
-/**
- * Backend that writes to stderr and with color
- */
-class ColorConsoleBackend : public Backend {
-public:
-    ~ColorConsoleBackend() override;
-
-    static const char* Name() {
-        return "color_console";
-    }
-
-    const char* GetName() const override {
-        return Name();
-    }
-    void Write(const Entry& entry) override;
-};
+/// Initializes the logging system. This should be the first thing called in main.
+void Initialize();
 
-/**
- * Backend that writes to a file passed into the constructor
- */
-class FileBackend : public Backend {
-public:
-    explicit FileBackend(const std::filesystem::path& filename);
-    ~FileBackend() override;
-
-    static const char* Name() {
-        return "file";
-    }
-
-    const char* GetName() const override {
-        return Name();
-    }
-
-    void Write(const Entry& entry) override;
-
-private:
-    std::unique_ptr<FS::IOFile> file;
-    std::size_t bytes_written = 0;
-};
-
-/**
- * Backend that writes to Visual Studio's output window
- */
-class DebuggerBackend : public Backend {
-public:
-    ~DebuggerBackend() override;
-
-    static const char* Name() {
-        return "debugger";
-    }
-    const char* GetName() const override {
-        return Name();
-    }
-    void Write(const Entry& entry) override;
-};
-
-void AddBackend(std::unique_ptr<Backend> backend);
-
-void RemoveBackend(std::string_view backend_name);
-
-Backend* GetBackend(std::string_view backend_name);
+void DisableLoggingInTests();
 
 /**
- * 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
- * never get the message
+ * The global filter will prevent any messages from even being processed if they are filtered.
  */
 void SetGlobalFilter(const Filter& filter);
-} // namespace Common::Log
\ No newline at end of file
+
+void SetColorConsoleBackendEnabled(bool enabled);
+} // namespace Common::Log
-- 
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