libcamera: base: log: Fix LogCategory creation issues

Each declaration of a LogCategory will create a new LogCategory, and
will be stored in an unordered_set Logger::categories_. This means that
when a plugin .so is unloaded and loaded, as happens when destructing
and creating a CamereManager, we'll get duplicate categories.

The Logger::registerCategory docs say "Log categories must have unique
names. If a category with the same name already exists this function
performs no operation.". The code does not comply with this.

We solve the issue with two changes:

Change the unordered_set to a vector for simplicity, as there's no need
for an unordered_set.

Instead of using the LogCategory constructor to create new categories in
_LOG_CATEGORY() macro, use a factory method. The factory method will
return either an existing LogCategory if one exists with the given name,
or a newly created one.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

include/libcamera/base/log.h

@@ -29,7 +29,7 @@ enum LogSeverity {
 class LogCategory
 {
 public:
-	explicit LogCategory(const char *name);
+	static LogCategory *create(const char *name);
 
 	const std::string &name() const { return name_; }
 	LogSeverity severity() const { return severity_; }
@@ -38,6 +38,8 @@ public:
 	static const LogCategory &defaultCategory();
 
 private:
+	explicit LogCategory(const char *name);
+
 	const std::string name_;
 	LogSeverity severity_;
 };
@@ -49,7 +51,7 @@ extern const LogCategory &_LOG_CATEGORY(name)();
 const LogCategory &_LOG_CATEGORY(name)()				\
 {									\
 	/* The instance will be deleted by the Logger destructor. */	\
-	static LogCategory *category = new LogCategory(#name);		\
+	static LogCategory *category = LogCategory::create(#name);	\
 	return *category;						\
 }
 

src/libcamera/base/log.cpp

@@ -314,10 +314,11 @@ private:
 
 	friend LogCategory;
 	void registerCategory(LogCategory *category);
+	LogCategory *findCategory(const char *name) const;
 
 	static bool destroyed_;
 
-	std::unordered_set<LogCategory *> categories_;
+	std::vector<LogCategory *> categories_;
 	std::list<std::pair<std::string, LogSeverity>> levels_;
 
 	std::shared_ptr<LogOutput> output_;
@@ -707,12 +708,12 @@ LogSeverity Logger::parseLogLevel(const std::string &level)
  * \brief Register a log category with the logger
  * \param[in] category The log category
  *
- * Log categories must have unique names. If a category with the same name
+ * Log categories must have unique names. It is invalid to call this function
- * already exists this function performs no operation.
+ * if a log category with the same name already exists.
  */
 void Logger::registerCategory(LogCategory *category)
 {
-	categories_.insert(category);
+	categories_.push_back(category);
 
 	const std::string &name = category->name();
 	for (const std::pair<std::string, LogSeverity> &level : levels_) {
@@ -736,6 +737,22 @@ void Logger::registerCategory(LogCategory *category)
 	}
 }
 
+/**
+ * \brief Find an existing log category with the given name
+ * \param[in] name Name of the log category
+ * \return The pointer to the found log category or nullptr if not found
+ */
+LogCategory *Logger::findCategory(const char *name) const
+{
+	if (auto it = std::find_if(categories_.begin(), categories_.end(),
+				   [name](auto c) { return c->name() == name; });
+	    it != categories_.end()) {
+		return *it;
+	}
+
+	return nullptr;
+}
+
 /**
  * \enum LogSeverity
  * Log message severity
@@ -760,6 +777,27 @@ void Logger::registerCategory(LogCategory *category)
  * and is used to control the log level per group.
  */
 
+/**
+ * \brief Create a new LogCategory or return an existing one
+ * \param[in] name Name of the log category
+ *
+ * Create and return a new LogCategory with the given name if such a category
+ * does not yet exist, or return the existing one.
+ *
+ * \return The pointer to the LogCategory
+ */
+LogCategory *LogCategory::create(const char *name)
+{
+	LogCategory *category = Logger::instance()->findCategory(name);
+
+	if (!category) {
+		category = new LogCategory(name);
+		Logger::instance()->registerCategory(category);
+	}
+
+	return category;
+}
+
 /**
  * \brief Construct a log category
  * \param[in] name The category name
@@ -767,7 +805,6 @@ void Logger::registerCategory(LogCategory *category)
 LogCategory::LogCategory(const char *name)
 	: name_(name), severity_(LogSeverity::LogInfo)
 {
-	Logger::instance()->registerCategory(this);
 }
 
 /**
@@ -804,7 +841,7 @@ void LogCategory::setSeverity(LogSeverity severity)
  */
 const LogCategory &LogCategory::defaultCategory()
 {
-	static const LogCategory *category = new LogCategory("default");
+	static const LogCategory *category = LogCategory::create("default");
 	return *category;
 }