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GDB is currently broken on all SPARC targets when using GCC 4.9. When trying to print any local variable: (gdb) p x can't compute CFA for this frame This is related to the fact that the compiler now generates DWARF 4 debugging info by default, and in particular that it now emits DW_OP_call_frame_cfa, which triggers a limitation in dwarf2_frame_cfa: /* This restriction could be lifted if other unwinders are known to compute the frame base in a way compatible with the DWARF unwinder. */ if (!frame_unwinder_is (this_frame, &dwarf2_frame_unwind) && !frame_unwinder_is (this_frame, &dwarf2_tailcall_frame_unwind)) error (_("can't compute CFA for this frame")); We couldn't append the dwarf2 unwinder to all SPARC targets because it does not work properly with StackGhost: https://www.sourceware.org/ml/gdb-patches/2014-07/msg00012.html We also later discovered that using the DWARF2 unwinder means using it for computing the function's return address, which is buggy when it comes to functions returning a struct (where the return address is saved-pc+12 instead of saved-pc+8). This is because GCC is emitting the info about the return address as %o7/%i7 instead of the actual return address. For functions that have debugging info, we compensate by looking at the function's return type and add the extra +4, but for function without debug info, we're stuck. EricB and I twisted the issue in all the directions we could think of, and unfortunately couldn't find a way to make it work without introduction one regression or another. But, stepping back a little, just removing the restriction seems to work well for us on all both sparc-elf and {sparc,sparc64}-solaris. After reviewing the previous discussions about this test, I could not figure out whether some unwinders were already known to have incompatible CFAs or if the concern was purely theoretical: https://www.sourceware.org/ml/gdb-patches/2009-06/msg00191.html https://www.sourceware.org/ml/gdb-patches/2009-07/msg00570.html https://www.sourceware.org/ml/gdb-patches/2009-09/msg00027.html At the moment, we took the approach of trying it out, and see what happens... gdb/ChangeLog: PR backtrace/16215: * dwarf2-frame.c (dwarf2_frame_cfa): Remove the restriction the frame unwinder must either be the dwarf2_frame_unwind or the dwarf2_tailcall_frame_unwind. Verify that this_frame's stack_addr is valid before calling get_frame_base. Throw an error if not valid. Tested on sparc-solaris and sparc-elf with AdaCore's testsuite (the FSF testsuite crashes all of AdaCore's solaris machines). |
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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.