Resending in text/plain, sorry for any extra spam... On Thu, Aug 13, 2015 at 4:44 PM, Ian Lance Taylor <i...@airs.com> wrote: > > FX <fxcoud...@gmail.com> writes: > > > 1. It appears that even on platforms with BACKTRACE_SUPPORTED == 0 > > (such as x86_64-apple-darwin), libbacktrace is built and able to > > perform a nonsymbolic backtrace (which appears accurate). Is that a > > feature? Can I rely on it? > > Yes, that is a feature. You should always get accurate PC values even > on systems where libbacktrace does not yet generate file/line > information. > > > > 2. The backtraces I get on x86_64-linux-gnu are missing symbols. The > > attached source file, compiled with “gfortran -g” with the attached > > patch, gives the following backtrace with libgfortran’s existing code, > > which uses unwind and calls to addr2line: > > > >> #0 0x7F4F6E333467 > >> #1 0x7F4F6E334C42 > >> #2 0x7F4F6E409308 > >> #3 0x4008A3 in bar at a.f90:9 > >> #4 0x4008C8 in foo at a.f90:5 > >> #5 0x4008AF in test at a.f90:2
Yes, the current implementation cannot resolve addresses from dynamic libraries, since those are loaded at a random offset and addr2line looks at the binary on disk and not the process image in memory. A workaround is to compile with "-g -static". > > > > > > with my patch using libbacktrace, I get: > > > >> 0x7f04f00f8c7d _gfortrani_show_backtrace > >> ../../../trunk/libgfortran/runtime/backtrace.c:112 > >> 0x7f04f00f9ac4 _gfortrani_sys_abort > >> ../../../trunk/libgfortran/runtime/error.c:176 > >> 0x7f04f01c8c78 _gfortran_abort > >> ../../../trunk/libgfortran/intrinsics/abort.c:33 > >> 0x4008a3 ??? > >> /home/fx/gcc/irun/a.f90:9 > >> 0x4008c8 ??? > >> /home/fx/gcc/irun/a.f90:5 > >> 0x4008af test > >> /home/fx/gcc/irun/a.f90:2 > >> 0x4008ff main > >> /home/fx/gcc/irun/a.f90:2 > > > > > > where the symbols for foo() and bar() are apparently not found, though > > the source location is. Am I missing something here? I’m attaching the > > output of “dwarfdump a.out” and the a.out executable file itself > > (gzipped). > > I don't know why this is not working. Everything looks fine in the > a.out that you sent. Unfortunately, I think you sent the one built > without libbacktrace. Can you send me the one built with libbacktrace? > Thanks. > > Ian You might also take a look at the patch posted to PR 54572 which was my attempt to use libbacktrace a few years ago. While I got symbolic backtraces working somewhat, unfortunately I never got it to work completely since it crashed somewhere in libbacktrace in some cases, but maybe whatever bugs caused that have been fixed in the meantime... -- Janne Blomqvist
