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The stub unwinder is used on AArch64 if the target's memory is not readable at the current PC. For example, the user could try to call at an invalid address such as 0x0, as covered in the gdb.base/signull.exp test case. Many GDB ports use a similar unwinder to handle this case too. If we purposely kill the inferior before examining the trace then we get the following issue: ~~~ ... (gdb) trace f Tracepoint 3 at 0x7fb7fc28c0 (gdb) tstart (gdb) continue ... (gdb) tstop (gdb) tsave /tmp/trace (gdb) kill ... (gdb) target tfile /tmp/trace ... (gdb) tfind Register 31 is not available. ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Found trace frame 0, tracepoint 3 #-1 0x0000007fb7fc28c0 in f () ... ^^^ ~~~ This patch teaches the stub unwinder to report to the core frame code with UNWIND_UNAVAILABLE when either the stack pointer of the return address are unavailable to read from the target. gdb/ChangeLog: * aarch64-tdep.c (aarch64_make_stub_cache): Set available_p and swallow NOT_AVAILABLE_ERROR. (aarch64_stub_this_id): Call frame_id_build_unavailable_stack if available_p is not set. (aarch64_stub_frame_unwind_stop_reason): New function. (aarch64_stub_unwind): Install it.
README for GNU development tools This directory contains various GNU compilers, assemblers, linkers, debuggers, etc., plus their support routines, definitions, and documentation. If you are receiving this as part of a GDB release, see the file gdb/README. If with a binutils release, see binutils/README; if with a libg++ release, see libg++/README, etc. That'll give you info about this package -- supported targets, how to use it, how to report bugs, etc. It is now possible to automatically configure and build a variety of tools with one command. To build all of the tools contained herein, run the ``configure'' script here, e.g.: ./configure make To install them (by default in /usr/local/bin, /usr/local/lib, etc), then do: make install (If the configure script can't determine your type of computer, give it the name as an argument, for instance ``./configure sun4''. You can use the script ``config.sub'' to test whether a name is recognized; if it is, config.sub translates it to a triplet specifying CPU, vendor, and OS.) If you have more than one compiler on your system, it is often best to explicitly set CC in the environment before running configure, and to also set CC when running make. For example (assuming sh/bash/ksh): CC=gcc ./configure make A similar example using csh: setenv CC gcc ./configure make Much of the code and documentation enclosed is copyright by the Free Software Foundation, Inc. See the file COPYING or COPYING.LIB in the various directories, for a description of the GNU General Public License terms under which you can copy the files. REPORTING BUGS: Again, see gdb/README, binutils/README, etc., for info on where and how to report problems.