Decode trace symbols only when trace requested (GCC)

components/common/cpp/include/ftl/exception.hpp

@@ -44,17 +44,25 @@ class exception : public std::exception
 		return msg_.c_str();
 	}
 
-    const char * trace () const throw () {
-        return trace_.c_str();
+	std::string trace() const throw () {
+		return decode_backtrace();
 	}
 
 	void ignore() const { processed_ = true; }
 
 	private:
+	std::string decode_backtrace() const;
+
 	std::string msg_;
-    std::string trace_;
 	mutable bool processed_;
+
+#ifdef __GNUC__
+	static const int TRACE_SIZE_MAX_ = 16;
+	void* trace_[TRACE_SIZE_MAX_];
+	int trace_size_;
+#endif
 };
+
 }
 
 #define FTL_Error(A) (ftl::exception(ftl::Formatter() << __FILE__ << ":" << __LINE__ << ": " << A))