FreeTDM: Move custom backtrace code into ftdm_backtrace_walk() and helper functions.

Portability fix for uClibc and other (linux) environments that lack execinfo.h.

ftdm_backtrace_walk() and related return FTDM_NOTIMPL and print a message
if backtraces are not available in the current environment.

Signed-off-by: Stefan Knoblich <stkn@openisdn.net>

libs/freetdm/src/include/freetdm.h

@@ -1814,6 +1814,40 @@ FT_DECLARE(void) ftdm_global_set_config_directory(const char *path);
 /*! \brief Check if the FTDM library is initialized and running */
 FT_DECLARE(ftdm_bool_t) ftdm_running(void);
 
+/**
+ * Generate a stack trace and invoke a callback function for each entry
+ * \param[in]	callback	Callback function, that is invoked for each stack symbol
+ * \param[in]	priv		(User-)Private data passed to the callback
+ * \retval
+ *	FTDM_SUCCESS	On success
+ *	FTDM_NOTIMPL	Backtraces are not available
+ *	FTDM_EINVAL	Invalid arguments (callback was NULL)
+ */
+FT_DECLARE(ftdm_status_t) ftdm_backtrace_walk(void (* callback)(const int tid, const void *addr, const char *symbol, void *priv), void *priv);
+
+/**
+ * Convenience function to print a backtrace for a span.
+ * \note	The backtrace is generated with FTDM_LOG_DEBUG log level.
+ * \param[in]	span	Span object
+ * \retval
+ *	FTDM_SUCCESS	On success
+ *	FTDM_NOTIMPL	Backtraces are not available
+ *	FTDM_EINVAL	Invalid arguments (e.g. span was NULL)
+ */
+FT_DECLARE(ftdm_status_t) ftdm_backtrace_span(ftdm_span_t *span);
+
+/**
+ * Convenience function to print a backtrace for a channel.
+ * \note	The backtrace is generated with FTDM_LOG_DEBUG log level.
+ * \param[in]	chan	Channel object
+ * \retval
+ *	FTDM_SUCCESS	On success
+ *	FTDM_NOTIMPL	Backtraces are not available
+ *	FTDM_EINVAL	Invalid arguments (e.g. chan was NULL)
+ */
+FT_DECLARE(ftdm_status_t) ftdm_backtrace_chan(ftdm_channel_t *chan);
+
+
 FT_DECLARE_DATA extern ftdm_logger_t ftdm_log;
 
 /*! \brief Basic transcoding function prototype */