If you don't want to take the "signal a different process that runs gdb on you" approach, which I think gby is advocating, you can also slightly alter your code to call open() on a crash log file and then backtrace_symbols_fd() with the fd returned by open() - both functions are async signal safe according to the glibc manual. You'll need still -rdynamic, of course. Also, from what I've seen, you still sometimes need to run addr2line on some addresses that the backtrace*() functions won't be able to decode.
Also note fork() is not async signal safe: http://article.gmane.org/gmane.linux.man/1893/match=fork+async, at least not on Linux. Neither is syslog(), as somebody already pointed out.
