Yep, this was my thought immediately. But probably this flag is not the one needed, as it enables complete C++ exception support - which turns on a couple of other things automatically.

"-funwind-tables" enables stack unwinding

"-fasynchronous-unwind-tables" makes the stack unwinding available for debuggers

"-fno-dwarf2-cfi-asm" makes the debugger unwind table "old style", so unwinding info goes into .eh_frame and .eh_frame_hdr section (or .ARM.extab and .ARM.exidx on ARM) instead of .debug.*

These sections are then parsed by the backtrace() family of glibc calls: https://www.gnu.org/software/libc/manual/html_node/Backtrace...

If you keep reading on, that was not the problem ;). The problem was missing glue code that would actually register the frames.