Created attachment 7155 [details]
The backtrace / backtrace_symbols / backtrace_symbols_fd interfaces do not work well when backtracing through calls to noreturn functions (a natural use case - a noreturn error-handling function might reasonably wish to print a backtrace).
This is illustrated by the attached testcase on x86_64. At least with some GCC versions, the call to a noreturn function has return address pointing to padding after the end of the calling function, meaning that it does not point inside that function and so a name for it cannot be found.
The backtrace interface is that the addresses are return addresses. But reliable backtracing requires additional information about whether frames are signal frame, in which case the return address points inside the relevant function, or not, in which case you should subtract 1 to be sure of being inside the relevant function. (That involves calling _Unwind_GetIPInfo instead of _Unwind_GetIP to get the relevant information.) So to support this case reliably, there should be new interfaces that handle this adjustment in some way.
(Old discussion started at: http://www.eglibc.org/archives/patches/msg01077.html .)