[v6,0/5] Modernize frame unwinders and add disable feature

  This patch series started with me trying to make it easier to test GDB's
ability to unwind using CFI data, to improve a previous patch I sent to
the list.

The first patch is just a minor change, storing frame unwinders in a
vector instead of through an unwinder table accessible using the
registry system. This isn't required (like I originally thought it was),
but it does make the whole system more readable in my opinion.

Patch 3 has the real meat of the modernization, making GDB use
polymorphism to handle frame unwinders. This is slightly slower than
using function pointers, but much more readable in my opinion. Also, as
noted by Thiago Bauermann, no frame unwinders that use the legacy class
ever pass a frame_data pointer, so that field was removed from those
unwinders.

As for the unwinder classes, they were chosen somewhat arbitrarily,
mostly based on where I found an unwinder and its name.

Patch 4 also reverts commit 3c3bb0580be0 since that patch pointed out
that if a more generic system was implemented it could be reverted.

All the documentation has been approved by Eli already.

Changes for v6:
* Patches 1 and 2 were approved by Simon
* Several cosmetic changes to patch 3 and 4
* New dealloc_cache default implementation (noop), and frame_unwind_legacy
  defaults to it if no function pointer is given.
* New prev_arch default implementation (getting the current arch), and
  frame_unwind_legacy defaults to it if no pointer is given
* Renamed "sniffer" to "sniff", to make it more clear what the method
  does
* Fixed some problems with the testcase.

Changes for v5:
* Reverted commit 3c3bb0580be0, with patch 4 following the advice on
  that commit
* on patch 3, some of the original functions were converted into the
  classes' methods instead of just passing the call along.
* some methods of frame_unwind_legacy were switched to be purely
  virtual

Changes for v4:
* Rebase on current master (No changes needed)
* improved documentation of unwinder classes follow Eli feedback
* added KFAIL to new test on patch 5 if running on 32 bit arm

Changes for v3:
* Fixed Linaro CI issue in 32 bit arm
* Fixed the few comments from Eli.
* Documented addition of unwinder class in the patch that adds it.

Changes for v2:
* Added back the test that checks if GDB can handle a mix of CUs with
  and without debuginfo in a single backtrace.
* Fixed all the nitpicks for style.
* Removed FRAME_UNWIND_ prefix when talking about classes
* Thoroughly changed the documentation, to be more readable

Guinevere Larsen (5):
  gdb: make gdbarch store a vector of frame unwinders
  gdb: add "unwinder class" to frame unwinders
  gdb: Migrate frame unwinders to use C++ classes
  gdb: introduce ability to disable frame unwinders
  gdb/testsuite: Test for a backtrace through object without debuginfo

 gdb/NEWS                                      |  21 +
 gdb/aarch64-tdep.c                            |  12 +-
 gdb/alpha-mdebug-tdep.c                       |   6 +-
 gdb/alpha-tdep.c                              |  12 +-
 gdb/amd64-obsd-tdep.c                         |   6 +-
 gdb/amd64-tdep.c                              |  24 +-
 gdb/amd64-windows-tdep.c                      |   6 +-
 gdb/amdgpu-tdep.c                             |   7 +-
 gdb/arc-tdep.c                                |  10 +-
 gdb/arch-utils.c                              |   8 +
 gdb/arm-tdep.c                                |  29 +-
 gdb/avr-tdep.c                                |   5 +-
 gdb/bfin-tdep.c                               |   6 +-
 gdb/bpf-tdep.c                                |   6 +-
 gdb/cris-tdep.c                               |  12 +-
 gdb/csky-tdep.c                               |  10 +-
 gdb/doc/gdb.texinfo                           |  64 +--
 gdb/dummy-frame.c                             |   8 +-
 gdb/dummy-frame.h                             |   2 +-
 gdb/dwarf2/frame-tailcall.c                   |   9 +-
 gdb/dwarf2/frame-tailcall.h                   |   2 +-
 gdb/dwarf2/frame.c                            |  46 +--
 gdb/dwarf2/frame.h                            |   6 -
 gdb/frame-unwind.c                            | 375 ++++++++++++++----
 gdb/frame-unwind.h                            | 157 +++++++-
 gdb/frame.c                                   |  21 +-
 gdb/frv-linux-tdep.c                          |   6 +-
 gdb/frv-tdep.c                                |   5 +-
 gdb/ft32-tdep.c                               |   6 +-
 gdb/gdbarch-gen.c                             |   6 +
 gdb/gdbarch.h                                 |   5 +
 gdb/gdbarch.py                                |   6 +
 gdb/h8300-tdep.c                              |   5 +-
 gdb/hppa-linux-tdep.c                         |   5 +-
 gdb/hppa-tdep.c                               |  17 +-
 gdb/i386-obsd-tdep.c                          |   5 +-
 gdb/i386-tdep.c                               |  30 +-
 gdb/ia64-tdep.c                               |  24 +-
 gdb/inline-frame.c                            |   5 +-
 gdb/inline-frame.h                            |   2 +-
 gdb/iq2000-tdep.c                             |   5 +-
 gdb/jit.c                                     |   6 +-
 gdb/lm32-tdep.c                               |   5 +-
 gdb/loongarch-tdep.c                          |   7 +-
 gdb/m32c-tdep.c                               |   5 +-
 gdb/m32r-linux-tdep.c                         |   5 +-
 gdb/m32r-tdep.c                               |   5 +-
 gdb/m68hc11-tdep.c                            |   5 +-
 gdb/m68k-linux-tdep.c                         |   6 +-
 gdb/m68k-tdep.c                               |   6 +-
 gdb/mep-tdep.c                                |   5 +-
 gdb/microblaze-tdep.c                         |   6 +-
 gdb/mips-sde-tdep.c                           |   6 +-
 gdb/mips-tdep.c                               |  24 +-
 gdb/mn10300-tdep.c                            |   5 +-
 gdb/moxie-tdep.c                              |   5 +-
 gdb/msp430-tdep.c                             |   5 +-
 gdb/nds32-tdep.c                              |  14 +-
 gdb/nios2-tdep.c                              |  12 +-
 gdb/or1k-tdep.c                               |   7 +-
 gdb/ppc-fbsd-tdep.c                           |   5 +-
 gdb/ppc-obsd-tdep.c                           |   5 +-
 gdb/python/py-unwind.c                        |  61 ++-
 gdb/record-btrace.c                           |  12 +-
 gdb/record.h                                  |   4 +-
 gdb/riscv-tdep.c                              |   8 +-
 gdb/rl78-tdep.c                               |   6 +-
 gdb/rs6000-aix-tdep.c                         |   5 +-
 gdb/rs6000-tdep.c                             |  12 +-
 gdb/rx-tdep.c                                 |  10 +-
 gdb/s12z-tdep.c                               |   7 +-
 gdb/s390-linux-tdep.c                         |   5 +-
 gdb/s390-tdep.c                               |  10 +-
 gdb/sentinel-frame.c                          |   8 +-
 gdb/sentinel-frame.h                          |   2 +-
 gdb/sh-tdep.c                                 |  11 +-
 gdb/sparc-netbsd-tdep.c                       |   6 +-
 gdb/sparc-obsd-tdep.c                         |   6 +-
 gdb/sparc-sol2-tdep.c                         |   6 +-
 gdb/sparc-tdep.c                              |   6 +-
 gdb/sparc64-fbsd-tdep.c                       |   6 +-
 gdb/sparc64-netbsd-tdep.c                     |   6 +-
 gdb/sparc64-obsd-tdep.c                       |  12 +-
 gdb/sparc64-sol2-tdep.c                       |   6 +-
 gdb/sparc64-tdep.c                            |   6 +-
 .../backtrace-through-cu-nodebug-caller.c     |  28 ++
 .../backtrace-through-cu-nodebug-main.c       |  32 ++
 .../gdb.base/backtrace-through-cu-nodebug.exp |  95 +++++
 .../gdb.base/frame-info-consistent.exp        |   6 +-
 gdb/testsuite/gdb.base/frame-unwind-disable.c |  21 +
 .../gdb.base/frame-unwind-disable.exp         | 137 +++++++
 gdb/testsuite/gdb.base/maint.exp              |   4 -
 gdb/tic6x-tdep.c                              |  12 +-
 gdb/tilegx-tdep.c                             |   5 +-
 gdb/tramp-frame.c                             |  70 +++-
 gdb/v850-tdep.c                               |   5 +-
 gdb/vax-tdep.c                                |   6 +-
 gdb/windows-tdep.c                            |  34 +-
 gdb/windows-tdep.h                            |  16 +-
 gdb/xstormy16-tdep.c                          |   5 +-
 gdb/xtensa-tdep.c                             |   7 +-
 gdb/z80-tdep.c                                |   7 +-
 102 files changed, 1315 insertions(+), 547 deletions(-)
 create mode 100644 gdb/testsuite/gdb.base/backtrace-through-cu-nodebug-caller.c
 create mode 100644 gdb/testsuite/gdb.base/backtrace-through-cu-nodebug-main.c
 create mode 100644 gdb/testsuite/gdb.base/backtrace-through-cu-nodebug.exp
 create mode 100644 gdb/testsuite/gdb.base/frame-unwind-disable.c
 create mode 100644 gdb/testsuite/gdb.base/frame-unwind-disable.exp