libcamera: base: Add Backtrace class

Create a new class to abstract generation and access to call stack
backtraces. The current implementation depends on the glibc backtrace()
implementation and is copied from the logger. Future development will
bring support for libunwind, transparently for the users of the class.

The logger backtrace implementation is dropped, replaced by usage of the
new Backtrace class.

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

src/libcamera/base/log.cpp

@@ -8,9 +8,6 @@
 #include <libcamera/base/log.h>
 
 #include <array>
-#if HAVE_BACKTRACE
-#include <execinfo.h>
-#endif
 #include <fstream>
 #include <iostream>
 #include <list>
@@ -23,6 +20,7 @@
 
 #include <libcamera/logging.h>
 
+#include <libcamera/base/backtrace.h>
 #include <libcamera/base/thread.h>
 #include <libcamera/base/utils.h>
 
@@ -418,31 +416,22 @@ void Logger::write(const LogMessage &msg)
  */
 void Logger::backtrace()
 {
-#if HAVE_BACKTRACE
 	std::shared_ptr<LogOutput> output = std::atomic_load(&output_);
 	if (!output)
 		return;
 
-	void *buffer[32];
-	int num_entries = ::backtrace(buffer, std::size(buffer));
-	char **strings = backtrace_symbols(buffer, num_entries);
-	if (!strings)
-		return;
-
-	std::ostringstream msg;
-	msg << "Backtrace:" << std::endl;
-
 	/*
 	 * Skip the first two entries that correspond to this function and
 	 * ~LogMessage().
 	 */
-	for (int i = 2; i < num_entries; ++i)
-		msg << strings[i] << std::endl;
+	std::string backtrace = Backtrace().toString(2);
+	if (backtrace.empty()) {
+		output->write("Backtrace not available\n");
+		return;
+	}
 
-	output->write(msg.str());
-
-	free(strings);
-#endif
+	output->write("Backtrace:\n");
+	output->write(backtrace);
 }
 
 /**