Paul Brook wrote: >>>> As I understand it, the ARM kernel can now do something similar. So, >>>> the only use for a __builtin_return_address(N) that used the frame >>>> pointer chain would be if the code were compiled with nonstandard >>>> options. >>> Correct. >> Well, but wouldn't it still be nice if __builtin_return_address(N) was >> implemented for N>0 by libcalling into the unwinder for you? Obviously >> this would still have to return NULL at runtime when you're running on a >> DW2 target without any EH frame data present in memory (and I guess it >> wouldn't work on SjLj targets either), but wouldn't it still be a nice >> convenience feature for users? > > There are sufficiently many caveats and system specific bits of weirdness > that > you probably just have to know what you're doing (or rely on backtrace(3) to > do it for you). > > IMHO builtins are for things that you can't do in normal C. So > __builtin_return_address(0) makes a lot of sense. Having it start guessing > how to do N>0 much less so.
I suggest we could contribute a version of backtrace.c for ARM to glibc. An example to follow is libc/sysdeps/ia64/backtrace.c. Andrew.
