Fix double timestamps in Wine STDERR logger

src/common/logging/common.cpp

@@ -41,8 +41,12 @@ constexpr char logging_verbosity_environment_variable[] =
 
 Logger::Logger(std::shared_ptr<std::ostream> stream,
                Verbosity verbosity_level,
-               std::string prefix)
-    : verbosity(verbosity_level), stream(stream), prefix(prefix) {}
+               std::string prefix,
+               bool prefix_timestamp)
+    : verbosity(verbosity_level),
+      stream(stream),
+      prefix(prefix),
+      prefix_timestamp(prefix_timestamp) {}
 
 Logger Logger::create_from_environment(std::string prefix) {
     auto env = boost::this_process::environment();
@@ -92,22 +96,26 @@ Logger Logger::create_wine_stderr() {
     // we want the STDERR redirection from the group host processes to still
     // function here
     return Logger(std::shared_ptr<std::ostream>(&std::cerr, [](auto*) {}),
-                  verbosity_level, "");
+                  verbosity_level, "", false);
 }
 
 void Logger::log(const std::string& message) {
-    const auto current_time = std::chrono::system_clock::now();
-    const std::time_t timestamp =
-        std::chrono::system_clock::to_time_t(current_time);
-
-    // How did C++ manage to get time formatting libraries without a way to
-    // actually get a timestamp in a threadsafe way? `localtime_r` in C++ is not
-    // portable but luckily we only have to support GCC anyway.
-    std::tm tm;
-    localtime_r(&timestamp, &tm);
-
     std::ostringstream formatted_message;
-    formatted_message << std::put_time(&tm, "%T") << " ";
+
+    if (prefix_timestamp) {
+        const auto current_time = std::chrono::system_clock::now();
+        const std::time_t timestamp =
+            std::chrono::system_clock::to_time_t(current_time);
+
+        // How did C++ manage to get time formatting libraries without a way to
+        // actually get a timestamp in a threadsafe way? `localtime_r` in C++ is
+        // not portable but luckily we only have to support GCC anyway.
+        std::tm tm;
+        localtime_r(&timestamp, &tm);
+
+        formatted_message << std::put_time(&tm, "%T") << " ";
+    }
+
     formatted_message << prefix;
     formatted_message << message;
     // Flushing a stringstream doesn't do anything, but we need to put a

src/common/logging/common.h

@@ -95,11 +95,18 @@ class Logger {
      *   `Logger::Verbosity` constants above for a description of the verbosity
      *   levels.
      * @param prefix An optional prefix for the logger. Useful for differentiate
-     *   messages coming from the Wine VST host.
+     *   messages coming from the Wine VST host. Should end with a single space
+     *   character.
+     * @param prefix_timestamp Whether the log messages should be prefixed with
+     *   a timestamp. The timestamp is added before `prefix`. This is set to
+     *   `false` in `create_wine_stderr()` because otherwise you would end up
+     *   with a second timestamp in the middle of the message (since all Wine
+     *   output gets relayed through the logger using `async_log_pipe_lines()`).
      */
     Logger(std::shared_ptr<std::ostream> stream,
            Verbosity verbosity_level,
-           std::string prefix = "");
+           std::string prefix = "",
+           bool prefix_timestamp = false);
 
     /**
      * Create a logger instance based on the set environment variables. See the
@@ -114,8 +121,6 @@ class Logger {
      * Create a special logger instance that outputs directly to STDERR without
      * any prefixes. This is used to be able to log filterable messages from the
      * Wine side of things.
-     *
-     * TODO: Don't prefix this with a timestamp
      */
     static Logger create_wine_stderr();
 
@@ -179,8 +184,14 @@ class Logger {
      * or a file stream.
      */
     std::shared_ptr<std::ostream> stream;
+
     /**
      * A prefix that gets prepended before every message.
      */
-    std::string prefix;
+    const std::string prefix;
+
+    /**
+     * Whether the log messages should be prefixed with a time stamp.
+     */
+    const bool prefix_timestamp;
 };