gdb: Migrate frame unwinders to use C++ classes

Frame unwinders have historically been a structure populated with
callback pointers, so that architectures (or other specific unwinders)
could install their own way to handle the inferior. However, since
moving to c++, we could use polymorphism to get the same functionality
in a more readable way. Polymorphism also makes it simpler to add new
functionality to all frame unwinders, since all that's required is
adding it to the base class.

As part of the changes to add support to disabling frame unwinders,
this commit makes the first baby step in  using polymorphism for the
frame unwinders, by making frame_unwind a virtual class, and adds 3 new
classes. The main class added is frame_unwind_legacy, which works the
same as the previous structs, using function pointers as callbacks. This
class was added to allow the transition to happen piecemeal. New
unwinders should instead follow the lead of the other 2 classes
implemented.

The other 2, frame_unwind_python and frame_unwind_trampoline, were added
because it seemed simpler at the moment to do that instead of reworking
the dynamic allocation to work with the legacy class, and can be used as
an example to future implementations.

gdb/aarch64-tdep.c

@@ -1204,16 +1204,16 @@ aarch64_prologue_prev_register (frame_info_ptr this_frame,
 }
 
 /* AArch64 prologue unwinder.  */
-static frame_unwind aarch64_prologue_unwind =
+static frame_unwind_legacy aarch64_prologue_unwind (
-{
   "aarch64 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   aarch64_prologue_frame_unwind_stop_reason,
   aarch64_prologue_this_id,
   aarch64_prologue_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 /* Allocate and fill in *THIS_CACHE with information about the prologue of
    *THIS_FRAME.  Do not do this is if *THIS_CACHE was already allocated.
@@ -1299,16 +1299,16 @@ aarch64_stub_unwind_sniffer (const struct frame_unwind *self,
 }
 
 /* AArch64 stub unwinder.  */
-static frame_unwind aarch64_stub_unwind =
+static frame_unwind_legacy aarch64_stub_unwind (
-{
   "aarch64 stub",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   aarch64_stub_frame_unwind_stop_reason,
   aarch64_stub_this_id,
   aarch64_prologue_prev_register,
   NULL,
   aarch64_stub_unwind_sniffer
-};
+);
 
 /* Return the frame base address of *THIS_FRAME.  */
 

gdb/alpha-mdebug-tdep.c

@@ -331,16 +331,16 @@ alpha_mdebug_frame_sniffer (const struct frame_unwind *self,
   return 1;
 }
 
-static const struct frame_unwind alpha_mdebug_frame_unwind =
+static const struct frame_unwind_legacy alpha_mdebug_frame_unwind (
-{
   "alpha mdebug",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   alpha_mdebug_frame_this_id,
   alpha_mdebug_frame_prev_register,
   NULL,
   alpha_mdebug_frame_sniffer
-};
+);
 
 static CORE_ADDR
 alpha_mdebug_frame_base_address (frame_info_ptr this_frame,

gdb/alpha-tdep.c

@@ -1007,16 +1007,16 @@ alpha_sigtramp_frame_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind alpha_sigtramp_frame_unwind =
+static const struct frame_unwind_legacy alpha_sigtramp_frame_unwind (
-{
   "alpha sigtramp",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   alpha_sigtramp_frame_this_id,
   alpha_sigtramp_frame_prev_register,
   NULL,
   alpha_sigtramp_frame_sniffer
-};
+);
 
 
 
@@ -1426,16 +1426,16 @@ alpha_heuristic_frame_prev_register (frame_info_ptr this_frame,
   return trad_frame_get_prev_register (this_frame, info->saved_regs, regnum);
 }
 
-static const struct frame_unwind alpha_heuristic_frame_unwind =
+static const struct frame_unwind_legacy alpha_heuristic_frame_unwind (
-{
   "alpha prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   alpha_heuristic_frame_this_id,
   alpha_heuristic_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 static CORE_ADDR
 alpha_heuristic_frame_base_address (frame_info_ptr this_frame,

gdb/amd64-obsd-tdep.c

@@ -402,19 +402,19 @@ amd64obsd_trapframe_sniffer (const struct frame_unwind *self,
 		   || (startswith (name, "Xintr"))));
 }
 
-static const struct frame_unwind amd64obsd_trapframe_unwind =
+static const struct frame_unwind_legacy amd64obsd_trapframe_unwind (
-{
   /* FIXME: kettenis/20051219: This really is more like an interrupt
      frame, but SIGTRAMP_FRAME would print <signal handler called>,
      which really is not what we want here.  */
   "amd64 openbsd trap",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   amd64obsd_trapframe_this_id,
   amd64obsd_trapframe_prev_register,
   NULL,
   amd64obsd_trapframe_sniffer
-};
+);
 
 
 static void

gdb/amd64-tdep.c

@@ -2658,16 +2658,16 @@ amd64_frame_prev_register (frame_info_ptr this_frame, void **this_cache,
   return frame_unwind_got_register (this_frame, regnum, regnum);
 }
 
-static const struct frame_unwind amd64_frame_unwind =
+static const struct frame_unwind_legacy amd64_frame_unwind (
-{
   "amd64 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   amd64_frame_unwind_stop_reason,
   amd64_frame_this_id,
   amd64_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 /* Generate a bytecode expression to get the value of the saved PC.  */
 
@@ -2804,16 +2804,16 @@ amd64_sigtramp_frame_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind amd64_sigtramp_frame_unwind =
+static const struct frame_unwind_legacy amd64_sigtramp_frame_unwind (
-{
   "amd64 sigtramp",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   amd64_sigtramp_frame_unwind_stop_reason,
   amd64_sigtramp_frame_this_id,
   amd64_sigtramp_frame_prev_register,
   NULL,
   amd64_sigtramp_frame_sniffer
-};
+);
 
 
 static CORE_ADDR
@@ -2996,27 +2996,27 @@ amd64_epilogue_frame_this_id (frame_info_ptr this_frame,
     (*this_id) = frame_id_build (cache->base + 16, cache->pc);
 }
 
-static const struct frame_unwind amd64_epilogue_override_frame_unwind =
+static const struct frame_unwind_legacy amd64_epilogue_override_frame_unwind (
-{
   "amd64 epilogue override",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   amd64_epilogue_frame_unwind_stop_reason,
   amd64_epilogue_frame_this_id,
   amd64_frame_prev_register,
   NULL,
   amd64_epilogue_override_frame_sniffer
-};
+);
 
-static const struct frame_unwind amd64_epilogue_frame_unwind =
+static const struct frame_unwind_legacy amd64_epilogue_frame_unwind (
-{
   "amd64 epilogue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   amd64_epilogue_frame_unwind_stop_reason,
   amd64_epilogue_frame_this_id,
   amd64_frame_prev_register,
   NULL, 
   amd64_epilogue_frame_sniffer
-};
+);
 
 static struct frame_id
 amd64_dummy_id (struct gdbarch *gdbarch, frame_info_ptr this_frame)

gdb/amd64-windows-tdep.c

@@ -1181,16 +1181,16 @@ amd64_windows_frame_this_id (frame_info_ptr this_frame, void **this_cache,
 
 /* Windows x64 SEH unwinder.  */
 
-static const struct frame_unwind amd64_windows_frame_unwind =
+static const struct frame_unwind_legacy amd64_windows_frame_unwind (
-{
   "amd64 windows",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   &amd64_windows_frame_this_id,
   &amd64_windows_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 /* Implement the "skip_prologue" gdbarch method.  */
 

gdb/amdgpu-tdep.c

@@ -892,9 +892,10 @@ amdgpu_frame_prev_register (frame_info_ptr this_frame, void **this_cache,
   return frame_unwind_got_register (this_frame, regnum, regnum);
 }
 
-static const frame_unwind amdgpu_frame_unwind = {
+static const frame_unwind_legacy amdgpu_frame_unwind (
   "amdgpu",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   amdgpu_frame_this_id,
   amdgpu_frame_prev_register,
@@ -902,7 +903,7 @@ static const frame_unwind amdgpu_frame_unwind = {
   default_frame_sniffer,
   nullptr,
   nullptr,
-};
+);
 
 static int
 print_insn_amdgpu (bfd_vma memaddr, struct disassemble_info *info)

gdb/arc-tdep.c

@@ -1900,9 +1900,10 @@ arc_sigtramp_frame_sniffer (const struct frame_unwind *self,
    the fallback unwinder, we use the default frame sniffer, which always
    accepts the frame.  */
 
-static const struct frame_unwind arc_frame_unwind = {
+static const struct frame_unwind_legacy arc_frame_unwind (
   "arc prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   arc_frame_this_id,
   arc_frame_prev_register,
@@ -1910,15 +1911,16 @@ static const struct frame_unwind arc_frame_unwind = {
   default_frame_sniffer,
   NULL,
   NULL
-};
+);
 
 /* Structure defining the ARC signal frame unwind functions.  Custom
    sniffer is used, because this frame must be accepted only in the right
    context.  */
 
-static const struct frame_unwind arc_sigtramp_frame_unwind = {
+static const struct frame_unwind_legacy arc_sigtramp_frame_unwind (
   "arc sigtramp",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   arc_sigtramp_frame_this_id,
   arc_sigtramp_frame_prev_register,
@@ -1926,7 +1928,7 @@ static const struct frame_unwind arc_sigtramp_frame_unwind = {
   arc_sigtramp_frame_sniffer,
   NULL,
   NULL
-};
+);
 
 
 static const struct frame_base arc_normal_base = {

gdb/arch-utils.c

@@ -1218,6 +1218,14 @@ obstack *gdbarch_obstack (gdbarch *arch)
 
 /* See gdbarch.h.  */
 
+std::vector<const frame_unwind*>&
+gdbarch_get_unwinder_list (struct gdbarch *arch)
+{
+  return arch->unwinders;
+}
+
+/* See gdbarch.h.  */
+
 char *
 gdbarch_obstack_strdup (struct gdbarch *arch, const char *string)
 {

gdb/arm-tdep.c

@@ -2469,9 +2469,10 @@ arm_prologue_prev_register (frame_info_ptr this_frame,
 				       prev_regnum);
 }
 
-static frame_unwind arm_prologue_unwind = {
+static frame_unwind_legacy arm_prologue_unwind = {
   "arm prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   arm_prologue_unwind_stop_reason,
   arm_prologue_this_id,
   arm_prologue_prev_register,
@@ -3188,9 +3189,10 @@ arm_exidx_unwind_sniffer (const struct frame_unwind *self,
   return 1;
 }
 
-struct frame_unwind arm_exidx_unwind = {
+struct frame_unwind_legacy arm_exidx_unwind = {
   "arm exidx",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   arm_prologue_this_id,
   arm_prologue_prev_register,
@@ -3297,16 +3299,16 @@ arm_epilogue_frame_sniffer (const struct frame_unwind *self,
 
 /* Frame unwinder from epilogue.  */
 
-static const struct frame_unwind arm_epilogue_frame_unwind =
+static const struct frame_unwind_legacy arm_epilogue_frame_unwind (
-{
   "arm epilogue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   arm_epilogue_frame_this_id,
   arm_epilogue_frame_prev_register,
   NULL,
-  arm_epilogue_frame_sniffer,
+  arm_epilogue_frame_sniffer
-};
+);
 
 /* Recognize GCC's trampoline for thumb call-indirect.  If we are in a
    trampoline, return the target PC.  Otherwise return 0.
@@ -3427,15 +3429,16 @@ arm_stub_unwind_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-struct frame_unwind arm_stub_unwind = {
+struct frame_unwind_legacy arm_stub_unwind (
   "arm stub",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   arm_stub_this_id,
   arm_prologue_prev_register,
   NULL,
   arm_stub_unwind_sniffer
-};
+);
 
 /* Put here the code to store, into CACHE->saved_regs, the addresses
    of the saved registers of frame described by THIS_FRAME.  CACHE is
@@ -3952,16 +3955,16 @@ arm_m_exception_unwind_sniffer (const struct frame_unwind *self,
 /* Frame unwinder for M-profile exceptions (EXC_RETURN on stack),
    lockup and secure/nonsecure interstate function calls (FNC_RETURN).  */
 
-struct frame_unwind arm_m_exception_unwind =
+struct frame_unwind_legacy arm_m_exception_unwind (
-{
   "arm m exception lockup sec_fnc",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   arm_m_exception_frame_unwind_stop_reason,
   arm_m_exception_this_id,
   arm_m_exception_prev_register,
   NULL,
   arm_m_exception_unwind_sniffer
-};
+);
 
 static CORE_ADDR
 arm_normal_frame_base (frame_info_ptr this_frame, void **this_cache)

gdb/avr-tdep.c

@@ -1155,15 +1155,16 @@ avr_frame_prev_register (frame_info_ptr this_frame,
   return trad_frame_get_prev_register (this_frame, info->saved_regs, regnum);
 }
 
-static const struct frame_unwind avr_frame_unwind = {
+static const struct frame_unwind_legacy avr_frame_unwind (
   "avr prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   avr_frame_this_id,
   avr_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 static CORE_ADDR
 avr_frame_base_address (frame_info_ptr this_frame, void **this_cache)

gdb/bfin-tdep.c

@@ -372,16 +372,16 @@ bfin_frame_prev_register (frame_info_ptr this_frame,
   return frame_unwind_got_register (this_frame, regnum, regnum);
 }
 
-static const struct frame_unwind bfin_frame_unwind =
+static const struct frame_unwind_legacy bfin_frame_unwind (
-{
   "bfin prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   bfin_frame_this_id,
   bfin_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 /* Check for "[--SP] = <reg>;" insns.  These are appear in function
    prologues to save misc registers onto the stack.  */

gdb/bpf-tdep.c

@@ -182,16 +182,16 @@ bpf_frame_prev_register (frame_info_ptr this_frame,
 
 /* Frame unwinder machinery for BPF.  */
 
-static const struct frame_unwind bpf_frame_unwind =
+static const struct frame_unwind_legacy bpf_frame_unwind (
-{
   "bpf prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   bpf_frame_unwind_stop_reason,
   bpf_frame_this_id,
   bpf_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 
 /* Breakpoints.  */

gdb/cris-tdep.c

@@ -435,16 +435,16 @@ cris_sigtramp_frame_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind cris_sigtramp_frame_unwind =
+static const struct frame_unwind_legacy cris_sigtramp_frame_unwind (
-{
   "cris sigtramp",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   cris_sigtramp_frame_this_id,
   cris_sigtramp_frame_prev_register,
   NULL,
   cris_sigtramp_frame_sniffer
-};
+);
 
 static int
 crisv32_single_step_through_delay (struct gdbarch *gdbarch,
@@ -900,16 +900,16 @@ cris_push_dummy_call (struct gdbarch *gdbarch, struct value *function,
   return sp;
 }
 
-static const struct frame_unwind cris_frame_unwind = 
+static const struct frame_unwind_legacy cris_frame_unwind (
-{
   "cris prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   cris_frame_this_id,
   cris_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 static CORE_ADDR
 cris_frame_base_address (frame_info_ptr this_frame, void **this_cache)

gdb/csky-tdep.c

@@ -2159,9 +2159,10 @@ csky_frame_prev_register (frame_info_ptr this_frame,
 /* Data structures for the normal prologue-analysis-based
    unwinder.  */
 
-static const struct frame_unwind csky_unwind_cache = {
+static const struct frame_unwind_legacy csky_unwind_cache (
   "cski prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   csky_frame_this_id,
   csky_frame_prev_register,
@@ -2169,7 +2170,7 @@ static const struct frame_unwind csky_unwind_cache = {
   default_frame_sniffer,
   NULL,
   NULL
-};
+);
 
 static CORE_ADDR
 csky_check_long_branch (frame_info_ptr frame, CORE_ADDR pc)
@@ -2293,15 +2294,16 @@ csky_stub_prev_register (frame_info_ptr this_frame,
 				       prev_regnum);
 }
 
-static frame_unwind csky_stub_unwind = {
+static frame_unwind_legacy csky_stub_unwind (
   "csky stub",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   csky_stub_this_id,
   csky_stub_prev_register,
   NULL,
   csky_stub_unwind_sniffer
-};
+  );
 
 /* Implement the this_base, this_locals, and this_args hooks
    for the normal unwinder.  */

gdb/dummy-frame.c

@@ -376,16 +376,16 @@ dummy_frame_this_id (frame_info_ptr this_frame,
   (*this_id) = cache->this_id;
 }
 
-const struct frame_unwind dummy_frame_unwind =
+const struct frame_unwind_legacy dummy_frame_unwind (
-{
   "dummy",
   DUMMY_FRAME,
+  FRAME_UNWIND_GDB,
   default_frame_unwind_stop_reason,
   dummy_frame_this_id,
   dummy_frame_prev_register,
   NULL,
-  dummy_frame_sniffer,
+  dummy_frame_sniffer
-};
+);
 
 /* See dummy-frame.h.  */
 

gdb/dummy-frame.h

@@ -54,7 +54,7 @@ extern void dummy_frame_discard (frame_id dummy_id, thread_info *thread);
 /* If the PC falls in a dummy frame, return a dummy frame
    unwinder.  */
 
-extern const struct frame_unwind dummy_frame_unwind;
+extern const struct frame_unwind_legacy dummy_frame_unwind;
 
 /* Destructor for dummy_frame.  DATA is supplied by registrant.
    REGISTERS_VALID is 1 for dummy_frame_pop, 0 for dummy_frame_discard.  */

gdb/dwarf2/frame-tailcall.c

@@ -469,10 +469,10 @@ tailcall_frame_prev_arch (frame_info_ptr this_frame,
 /* Virtual tail call frame unwinder if dwarf2_tailcall_sniffer_first finds
    a chain to create.  */
 
-const struct frame_unwind dwarf2_tailcall_frame_unwind =
+const struct frame_unwind_legacy dwarf2_tailcall_frame_unwind (
-{
   "dwarf2 tailcall",
   TAILCALL_FRAME,
+  FRAME_UNWIND_DEBUGINFO,
   default_frame_unwind_stop_reason,
   tailcall_frame_this_id,
   tailcall_frame_prev_register,
@@ -480,7 +480,7 @@ const struct frame_unwind dwarf2_tailcall_frame_unwind =
   tailcall_frame_sniffer,
   tailcall_frame_dealloc_cache,
   tailcall_frame_prev_arch
-};
+);
 
 void _initialize_tailcall_frame ();
 void

gdb/dwarf2/frame-tailcall.h

@@ -34,6 +34,6 @@ extern struct value *
   dwarf2_tailcall_prev_register_first (frame_info_ptr this_frame,
 				       void **tailcall_cachep, int regnum);
 
-extern const struct frame_unwind dwarf2_tailcall_frame_unwind;
+extern const struct frame_unwind_legacy dwarf2_tailcall_frame_unwind;
 
 #endif /* !DWARF2_FRAME_TAILCALL_H */

gdb/dwarf2/frame.c

@@ -1332,30 +1332,30 @@ dwarf2_frame_sniffer (const struct frame_unwind *self,
   if (fde->cie->signal_frame
       || dwarf2_frame_signal_frame_p (get_frame_arch (this_frame),
 				      this_frame))
-    return self->type == SIGTRAMP_FRAME;
+    return self->type () == SIGTRAMP_FRAME;
 
-  if (self->type != NORMAL_FRAME)
+  if (self->type () != NORMAL_FRAME)
     return 0;
 
   return 1;
 }
 
-static const struct frame_unwind dwarf2_frame_unwind =
+static const struct frame_unwind_legacy dwarf2_frame_unwind (
-{
   "dwarf2",
   NORMAL_FRAME,
+  FRAME_UNWIND_DEBUGINFO,
   dwarf2_frame_unwind_stop_reason,
   dwarf2_frame_this_id,
   dwarf2_frame_prev_register,
   NULL,
   dwarf2_frame_sniffer,
   dwarf2_frame_dealloc_cache
-};
+);
 
-static const struct frame_unwind dwarf2_signal_frame_unwind =
+static const struct frame_unwind_legacy dwarf2_signal_frame_unwind (
-{
   "dwarf2 signal",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_DEBUGINFO,
   dwarf2_frame_unwind_stop_reason,
   dwarf2_frame_this_id,
   dwarf2_frame_prev_register,
@@ -1364,7 +1364,7 @@ static const struct frame_unwind dwarf2_signal_frame_unwind =
 
   /* TAILCALL_CACHE can never be in such frame to need dealloc_cache.  */
   NULL
-};
+);
 
 /* Append the DWARF-2 frame unwinders to GDBARCH's list.  */
 

gdb/frame-unwind.c

@@ -31,49 +31,16 @@
 #include "cli/cli-cmds.h"
 #include "inferior.h"
 
-struct frame_unwind_table_entry
+/* If an unwinder should be prepended to the list, this is the
+   index in which it should be inserted.  */
+static int osabi_start = -1;
+
+/* Start the table out with a few default sniffers.  OSABI code
+   can't override this.  */
+static void
+initialize_frame_unwind_table (std::vector<const frame_unwind*>& table)
 {
-  const struct frame_unwind *unwinder;
+  table.push_back (&dummy_frame_unwind);
-  struct frame_unwind_table_entry *next;
-};
-
-struct frame_unwind_table
-{
-  struct frame_unwind_table_entry *list = nullptr;
-  /* The head of the OSABI part of the search list.  */
-  struct frame_unwind_table_entry **osabi_head = nullptr;
-};
-
-static const registry<gdbarch>::key<struct frame_unwind_table>
-     frame_unwind_data;
-
-/* A helper function to add an unwinder to a list.  LINK says where to
-   install the new unwinder.  The new link is returned.  */
-
-static struct frame_unwind_table_entry **
-add_unwinder (struct obstack *obstack, const struct frame_unwind *unwinder,
-	      struct frame_unwind_table_entry **link)
-{
-  *link = OBSTACK_ZALLOC (obstack, struct frame_unwind_table_entry);
-  (*link)->unwinder = unwinder;
-  return &(*link)->next;
-}
-
-static struct frame_unwind_table *
-get_frame_unwind_table (struct gdbarch *gdbarch)
-{
-  struct frame_unwind_table *table = frame_unwind_data.get (gdbarch);
-  if (table != nullptr)
-    return table;
-
-  table = new frame_unwind_table;
-
-  /* Start the table out with a few default sniffers.  OSABI code
-     can't override this.  */
-  struct frame_unwind_table_entry **link = &table->list;
-
-  struct obstack *obstack = gdbarch_obstack (gdbarch);
-  link = add_unwinder (obstack, &dummy_frame_unwind, link);
   /* The DWARF tailcall sniffer must come before the inline sniffer.
      Otherwise, we can end up in a situation where a DWARF frame finds
      tailcall information, but then the inline sniffer claims a frame
@@ -81,41 +48,71 @@ get_frame_unwind_table (struct gdbarch *gdbarch)
      safe to do always because the tailcall sniffer can only ever be
      activated if the newer frame was created using the DWARF
      unwinder, and it also found tailcall information.  */
-  link = add_unwinder (obstack, &dwarf2_tailcall_frame_unwind, link);
+  table.push_back (&dwarf2_tailcall_frame_unwind);
-  link = add_unwinder (obstack, &inline_frame_unwind, link);
+  table.push_back (&inline_frame_unwind);
 
   /* The insertion point for OSABI sniffers.  */
-  table->osabi_head = link;
+  osabi_start = table.size ();
-  frame_unwind_data.set (gdbarch, table);
+}
+
+/* This function call retrieves the list of frame unwinders available in
+   GDBARCH.  If this list is empty, it is initialized before being
+   returned.  */
+static std::vector<const frame_unwind*>&
+get_frame_unwind_table (struct gdbarch *gdbarch)
+{
+  std::vector<const frame_unwind*>& table = gdbarch_get_unwinder_list (gdbarch);
+  if (table.size () == 0)
+    initialize_frame_unwind_table (table);
 
   return table;
 }
 
+static const char *
+frame_unwinder_class_str (frame_unwind_class uclass)
+{
+  switch (uclass)
+    {
+      case FRAME_UNWIND_GDB:
+	return "FRAME_UNWIND_GDB";
+
+      case FRAME_UNWIND_EXTENSION:
+	return "FRAME_UNWIND_EXTENSION";
+
+      case FRAME_UNWIND_DEBUGINFO:
+	return "FRAME_UNWIND_DEBUGINFO";
+
+      case FRAME_UNWIND_ARCH:
+	return "FRAME_UNWIND_ARCH";
+
+      default:
+	return "<unknown class>";
+    };
+}
+
 void
 frame_unwind_prepend_unwinder (struct gdbarch *gdbarch,
 				const struct frame_unwind *unwinder)
 {
-  struct frame_unwind_table *table = get_frame_unwind_table (gdbarch);
+  std::vector<const frame_unwind*>& table = get_frame_unwind_table (gdbarch);
-  struct frame_unwind_table_entry *entry;
 
-  /* Insert the new entry at the start of the list.  */
+  gdb_assert (osabi_start >= 0);
-  entry = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_unwind_table_entry);
+
-  entry->unwinder = unwinder;
+  table.push_back (unwinder);
-  entry->next = (*table->osabi_head);
+
-  (*table->osabi_head) = entry;
+  /* Bubble the new entry up to where new unwinders are allowed to be
+     inserterd.  */
+  for (int i = table.size() - 1; i > osabi_start; i--)
+    std::swap(table[i], table[i-1]);
 }
 
 void
 frame_unwind_append_unwinder (struct gdbarch *gdbarch,
 			      const struct frame_unwind *unwinder)
 {
-  struct frame_unwind_table *table = get_frame_unwind_table (gdbarch);
+  std::vector<const frame_unwind*>& table = get_frame_unwind_table (gdbarch);
-  struct frame_unwind_table_entry **ip;
 
-  /* Find the end of the list and insert the new entry there.  */
+  table.push_back (unwinder);
-  for (ip = table->osabi_head; (*ip) != NULL; ip = &(*ip)->next);
-  (*ip) = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_unwind_table_entry);
-  (*ip)->unwinder = unwinder;
 }
 
 /* Call SNIFFER from UNWINDER.  If it succeeded set UNWINDER for
@@ -134,7 +131,7 @@ frame_unwind_try_unwinder (frame_info_ptr this_frame, void **this_cache,
 
   try
     {
-      frame_debug_printf ("trying unwinder \"%s\"", unwinder->name);
+      frame_debug_printf ("trying unwinder \"%s\"", unwinder->name ());
       res = unwinder->sniffer (unwinder, this_frame, this_cache);
     }
   catch (const gdb_exception &ex)
@@ -188,9 +185,6 @@ frame_unwind_find_by_frame (frame_info_ptr this_frame, void **this_cache)
   FRAME_SCOPED_DEBUG_ENTER_EXIT;
   frame_debug_printf ("this_frame=%d", frame_relative_level (this_frame));
 
-  struct gdbarch *gdbarch = get_frame_arch (this_frame);
-  struct frame_unwind_table *table = get_frame_unwind_table (gdbarch);
-  struct frame_unwind_table_entry *entry;
   const struct frame_unwind *unwinder_from_target;
 
   unwinder_from_target = target_get_unwinder ();
@@ -205,8 +199,10 @@ frame_unwind_find_by_frame (frame_info_ptr this_frame, void **this_cache)
 				   unwinder_from_target))
     return;
 
-  for (entry = table->list; entry != NULL; entry = entry->next)
+  struct gdbarch *gdbarch = get_frame_arch (this_frame);
-    if (frame_unwind_try_unwinder (this_frame, this_cache, entry->unwinder))
+  std::vector<const frame_unwind*> table = get_frame_unwind_table (gdbarch);
+  for (auto unwinder: table)
+    if (frame_unwind_try_unwinder (this_frame, this_cache, unwinder))
       return;
 
   internal_error (_("frame_unwind_find_by_frame failed"));
@@ -341,29 +337,103 @@ frame_unwind_got_address (frame_info_ptr frame, int regnum,
   return reg_val;
 }
 
+/* See frame-unwind.h.  */
+
+enum unwind_stop_reason
+frame_unwind::stop_reason (frame_info_ptr this_frame,
+				   void **this_prologue_cache) const
+{
+  return default_frame_unwind_stop_reason (this_frame, this_prologue_cache);
+}
+
+/* See frame-unwind.h.  */
+
+int
+frame_unwind::sniffer (const struct frame_unwind *self,
+		frame_info_ptr this_frame,
+		void **this_prologue_cache) const
+{
+  return 1;
+}
+
+/* This method just passes the parameters to the callback pointer.  */
+enum unwind_stop_reason
+frame_unwind_legacy::stop_reason (frame_info_ptr this_frame,
+				  void **this_prologue_cache) const
+{
+  return stop_reason_p (this_frame, this_prologue_cache);
+}
+
+/* This method just passes the parameters to the callback pointer.  */
+void
+frame_unwind_legacy::this_id (frame_info_ptr this_frame,
+			      void **this_prologue_cache,
+			      struct frame_id *id) const
+{
+  return this_id_p (this_frame, this_prologue_cache, id);
+}
+
+/* This method just passes the parameters to the callback pointer.  */
+struct value *
+frame_unwind_legacy::prev_register (frame_info_ptr this_frame,
+				void **this_prologue_cache,
+				int regnum) const
+{
+  return prev_register_p (this_frame, this_prologue_cache, regnum);
+}
+
+/* This method just passes the parameters to the callback pointer.  */
+int
+frame_unwind_legacy::sniffer (const struct frame_unwind *self,
+		frame_info_ptr this_frame,
+		void **this_prologue_cache) const
+{
+  return sniffer_p (self, this_frame, this_prologue_cache);
+}
+
+/* This method just passes the parameters to the callback pointer.  */
+void
+frame_unwind_legacy::dealloc_cache (frame_info *self, void *this_cache) const
+{
+  if (dealloc_cache_p != nullptr)
+    dealloc_cache_p (self, this_cache);
+}
+
+/* This method just passes the parameters to the callback pointer.  */
+struct gdbarch *
+frame_unwind_legacy::prev_arch (frame_info_ptr this_frame,
+			      void **this_prologue_cache) const
+{
+  if (prev_arch_p == nullptr)
+    error (_("No prev_arch callback installed"));
+  return prev_arch_p (this_frame, this_prologue_cache);
+}
+
 /* Implement "maintenance info frame-unwinders" command.  */
 
 static void
 maintenance_info_frame_unwinders (const char *args, int from_tty)
 {
   gdbarch *gdbarch = current_inferior ()->arch ();
-  struct frame_unwind_table *table = get_frame_unwind_table (gdbarch);
+  std::vector<const frame_unwind*> table = get_frame_unwind_table (gdbarch);
 
   ui_out *uiout = current_uiout;
-  ui_out_emit_table table_emitter (uiout, 2, -1, "FrameUnwinders");
+  ui_out_emit_table table_emitter (uiout, 3, -1, "FrameUnwinders");
   uiout->table_header (27, ui_left, "name", "Name");
   uiout->table_header (25, ui_left, "type", "Type");
+  uiout->table_header (25, ui_left, "class", "Class");
   uiout->table_body ();
 
-  for (struct frame_unwind_table_entry *entry = table->list; entry != NULL;
+  for (const struct frame_unwind* unwinder: table)
-       entry = entry->next)
     {
-      const char *name = entry->unwinder->name;
+      const char *name = unwinder->name ();
-      const char *type = frame_type_str (entry->unwinder->type);
+      const char *type = frame_type_str (unwinder->type ());
+      const char *uclass = frame_unwinder_class_str (unwinder->unwinder_class ());
 
       ui_out_emit_list tuple_emitter (uiout, nullptr);
       uiout->field_string ("name", name);
       uiout->field_string ("type", type);
+      uiout->field_string ("class", uclass);
       uiout->text ("\n");
     }
 }

gdb/frame-unwind.h

@@ -156,21 +156,150 @@ typedef void (frame_dealloc_cache_ftype) (frame_info *self,
 typedef struct gdbarch *(frame_prev_arch_ftype) (frame_info_ptr this_frame,
 						 void **this_prologue_cache);
 
-struct frame_unwind
+enum frame_unwind_class {
+  FRAME_UNWIND_GDB,
+  FRAME_UNWIND_EXTENSION,
+  FRAME_UNWIND_DEBUGINFO,
+  FRAME_UNWIND_ARCH,
+};
+
+class frame_unwind
 {
-  const char *name;
+private:
+  const char *m_name;
   /* The frame's type.  Should this instead be a collection of
      predicates that test the frame for various attributes?  */
-  enum frame_type type;
+  enum frame_type m_type;
+  /* What kind of unwinder is this.  It generally follows from where
+     the unwinder was added or where it looks for information to do the
+     unwinding.  */
+  enum frame_unwind_class m_unwinder_class;
+  const struct frame_data *m_unwind_data;
+public:
+  frame_unwind (const char *n, frame_type t, frame_unwind_class c,
+		       const struct frame_data *d)
+    : m_name (n), m_type (t), m_unwinder_class (c), m_unwind_data (d) { }
+
+  const char *name () const
+  {
+    return m_name;
+  }
+
+  enum frame_type type () const
+  {
+    return m_type;
+  }
+
+  enum frame_unwind_class unwinder_class () const
+  {
+    return m_unwinder_class;
+  }
+
+  const struct frame_data *unwind_data () const
+  {
+    return m_unwind_data;
+  }
+
+  /* Default stop_reason function.  It reports NO_REASON, unless the
+     frame is the outermost.  */
+  virtual enum unwind_stop_reason stop_reason (frame_info_ptr this_frame,
+					       void **this_prologue_cache) const;
+
+  /* Default frame sniffer.  Will always return that the unwinder
+     is able to unwind the frame.  */
+  virtual int sniffer (const frame_unwind *self,
+		       frame_info_ptr this_frame,
+		       void **this_prologue_cache) const;
+
+  /* The following methods are here mostly for interface functionality.  They
+     all throw an error when called, as a safe way to check if an unwinder has
+     implemented the desired functionality.  */
+
+  /* Calculate the ID of the given frame using this unwinder.  */
+  virtual void this_id (frame_info_ptr this_frame, void **this_prologue_cache,
+			struct frame_id *id) const
+  {
+    error (_("No method this_id implemented for unwinder %s"), m_name);
+  }
+
+  /* Get the value of a register in a previous frame.  */
+  virtual struct value *prev_register (frame_info_ptr this_frame,
+					     void **this_prologue_cache,
+					     int regnum) const
+  {
+    error (_("No method prev_register implemented for unwinder %s"), m_name);
+  }
+  
+  /* Properly deallocate the cache.  */
+  virtual void dealloc_cache (frame_info *self, void *this_cache) const
+  {
+    error (_("No method dealloc_cache implemented for unwinder %s"), m_name);
+  }
+
+  /* Get the previous architecture.  */
+  virtual struct gdbarch *prev_arch (frame_info_ptr this_frame,
+				     void **this_prologue_cache) const
+  {
+    error (_("No method prev_arch implemented for unwinder %s"), m_name);
+  }
+};
+
+/* This is a legacy version of the frame unwinder.  The original struct
+   used function pointers for callbacks, this updated version has a
+   method that just passes the parameters along to the callback
+   pointer.  */
+class frame_unwind_legacy : public frame_unwind
+{
+public:
   /* Should an attribute indicating the frame's address-in-block go
      here?  */
-  frame_unwind_stop_reason_ftype *stop_reason;
+  frame_unwind_stop_reason_ftype *stop_reason_p;
-  frame_this_id_ftype *this_id;
+  frame_this_id_ftype *this_id_p;
-  frame_prev_register_ftype *prev_register;
+  frame_prev_register_ftype *prev_register_p;
-  const struct frame_data *unwind_data;
+  frame_sniffer_ftype *sniffer_p;
-  frame_sniffer_ftype *sniffer;
+  frame_dealloc_cache_ftype *dealloc_cache_p;
-  frame_dealloc_cache_ftype *dealloc_cache;
+  frame_prev_arch_ftype *prev_arch_p;
-  frame_prev_arch_ftype *prev_arch;
+//public:
+  frame_unwind_legacy (const char *n, frame_type t, frame_unwind_class c,
+		       frame_unwind_stop_reason_ftype *sr,
+		       frame_this_id_ftype *ti,
+		       frame_prev_register_ftype *pr,
+		       const struct frame_data *ud,
+		       frame_sniffer_ftype *s,
+		       frame_dealloc_cache_ftype *dc = nullptr,
+		       frame_prev_arch_ftype *pa = nullptr)
+  : frame_unwind (n, t, c, ud), stop_reason_p (sr),
+    this_id_p (ti), prev_register_p (pr), sniffer_p (s),
+    dealloc_cache_p (dc), prev_arch_p (pa) { }
+
+  /* This method just passes the parameters to the callback pointer.  */
+  enum unwind_stop_reason stop_reason (frame_info_ptr this_frame,
+					void **this_prologue_cache) const override;
+
+  /* This method just passes the parameters to the callback pointer.  */
+  void this_id (frame_info_ptr this_frame, void **this_prologue_cache,
+		 struct frame_id *id) const override;
+
+  /* This method just passes the parameters to the callback pointer.  */
+  struct value *prev_register (frame_info_ptr this_frame,
+				void **this_prologue_cache,
+				int regnum) const override;
+
+  /* This method just passes the parameters to the callback pointer.  */
+  int sniffer (const frame_unwind *self,
+		frame_info_ptr this_frame,
+		void **this_prologue_cache) const override;
+
+  /* This method just passes the parameters to the callback pointer.
+     It is safe to call this method if no callback is installed, it
+     just turns into a noop.  */
+  void dealloc_cache (frame_info *self, void *this_cache) const override;
+
+  /* This method just passes the parameters to the callback pointer.
+     If this function is called with no installed callback, this method
+     will error out.  Wrap calls in try-catch blocks.  */
+  struct gdbarch *prev_arch (frame_info_ptr this_frame,
+			      void **this_prologue_cache) const override;
 };
 
 /* Register a frame unwinder, _prepending_ it to the front of the

gdb/frame.c

@@ -268,12 +268,10 @@ frame_addr_hash_eq (const void *a, const void *b)
 static void
 frame_info_del (frame_info *frame)
 {
-  if (frame->prologue_cache != nullptr
+  if (frame->prologue_cache != nullptr)
-      && frame->unwind->dealloc_cache != nullptr)
     frame->unwind->dealloc_cache (frame, frame->prologue_cache);
 
-  if (frame->base_cache != nullptr
+  if (frame->base_cache != nullptr)
-      && frame->base->unwind->dealloc_cache != nullptr)
     frame->base->unwind->dealloc_cache (frame, frame->base_cache);
 }
 
@@ -486,12 +484,12 @@ frame_info::to_string () const
   res += string_printf ("{level=%d,", fi->level);
 
   if (fi->unwind != NULL)
-    res += string_printf ("type=%s,", frame_type_str (fi->unwind->type));
+    res += string_printf ("type=%s,", frame_type_str (fi->unwind->type ()));
   else
     res += "type=<unknown>,";
 
   if (fi->unwind != NULL)
-    res += string_printf ("unwinder=\"%s\",", fi->unwind->name);
+    res += string_printf ("unwinder=\"%s\",", fi->unwind->name ());
   else
     res += "unwinder=<unknown>,";
 
@@ -2356,7 +2354,7 @@ get_prev_frame_always_1 (frame_info_ptr this_frame)
      This check is valid only if this frame and the next frame are NORMAL.
      See the comment at frame_id_inner for details.  */
   if (get_frame_type (this_frame) == NORMAL_FRAME
-      && this_frame->next->unwind->type == NORMAL_FRAME
+      && this_frame->next->unwind->type () == NORMAL_FRAME
       && frame_id_inner (get_frame_arch (frame_info_ptr (this_frame->next)),
 			 get_frame_id (this_frame),
 			 get_frame_id (frame_info_ptr (this_frame->next))))
@@ -2952,7 +2950,7 @@ get_frame_type (frame_info_ptr frame)
     /* Initialize the frame's unwinder because that's what
        provides the frame's type.  */
     frame_unwind_find_by_frame (frame, &frame->prologue_cache);
-  return frame->unwind->type;
+  return frame->unwind->type ();
 }
 
 struct program_space *
@@ -3033,11 +3031,15 @@ frame_unwind_arch (frame_info_ptr next_frame)
       if (next_frame->unwind == NULL)
 	frame_unwind_find_by_frame (next_frame, &next_frame->prologue_cache);
 
-      if (next_frame->unwind->prev_arch != NULL)
+      try
-	arch = next_frame->unwind->prev_arch (next_frame,
+	{
-					      &next_frame->prologue_cache);
+	  arch = next_frame->unwind->prev_arch (next_frame,
-      else
+						&next_frame->prologue_cache);
-	arch = get_frame_arch (next_frame);
+	}
+      catch (gdb_exception &e)
+	{
+	  arch = get_frame_arch (next_frame);
+	}
 
       next_frame->prev_arch.arch = arch;
       next_frame->prev_arch.p = true;

gdb/frv-linux-tdep.c

@@ -332,16 +332,16 @@ frv_linux_sigtramp_frame_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind frv_linux_sigtramp_frame_unwind =
+static const struct frame_unwind_legacy frv_linux_sigtramp_frame_unwind (
-{
   "frv linux sigtramp",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   frv_linux_sigtramp_frame_this_id,
   frv_linux_sigtramp_frame_prev_register,
   NULL,
   frv_linux_sigtramp_frame_sniffer
-};
+);
 
 /* The FRV kernel defines ELF_NGREG as 46.  We add 2 in order to include
    the loadmap addresses in the register set.  (See below for more info.)  */

gdb/frv-tdep.c

@@ -1405,15 +1405,16 @@ frv_frame_prev_register (frame_info_ptr this_frame,
   return trad_frame_get_prev_register (this_frame, info->saved_regs, regnum);
 }
 
-static const struct frame_unwind frv_frame_unwind = {
+static const struct frame_unwind_legacy frv_frame_unwind (
   "frv prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   frv_frame_this_id,
   frv_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 static CORE_ADDR
 frv_frame_base_address (frame_info_ptr this_frame, void **this_cache)

gdb/ft32-tdep.c

@@ -524,16 +524,16 @@ ft32_frame_prev_register (frame_info_ptr this_frame,
   return frame_unwind_got_register (this_frame, regnum, regnum);
 }
 
-static const struct frame_unwind ft32_frame_unwind =
+static const struct frame_unwind_legacy ft32_frame_unwind (
-{
   "ft32 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   ft32_frame_this_id,
   ft32_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 /* Return the base address of this_frame.  */
 

gdb/gdbarch.c

@@ -27,6 +27,7 @@
 
 /* Maintain the struct gdbarch object.  */
 
+#include <vector>
 struct gdbarch
 {
   /* Has this architecture been fully initialized?  */
@@ -36,6 +37,8 @@ struct gdbarch
   auto_obstack obstack;
   /* Registry.  */
   registry<gdbarch> registry_fields;
+  /* list of frame unwinders.  */
+  std::vector<const frame_unwind *> unwinders;
 
   /* basic architectural information.  */
   const struct bfd_arch_info * bfd_arch_info;

gdb/gdbarch.h

@@ -30,6 +30,7 @@
 #include "displaced-stepping.h"
 #include "gdbsupport/gdb-checked-static-cast.h"
 #include "registry.h"
+#include "frame-unwind.h"
 
 struct floatformat;
 struct ui_file;
@@ -310,6 +311,10 @@ extern obstack *gdbarch_obstack (gdbarch *arch);
 
 #define GDBARCH_OBSTACK_ZALLOC(GDBARCH, TYPE)   obstack_zalloc<TYPE> (gdbarch_obstack ((GDBARCH)))
 
+/* Return the vector of unwinders stored in a gdbarch object.  */
+
+std::vector<const frame_unwind*>& gdbarch_get_unwinder_list (struct gdbarch *arch);
+
 /* Duplicate STRING, returning an equivalent string that's allocated on the
    obstack associated with GDBARCH.  The string is freed when the corresponding
    architecture is also freed.  */

gdb/gdbarch.py

@@ -125,6 +125,7 @@ with open("gdbarch.c", "w") as f:
     print(file=f)
     print("/* Maintain the struct gdbarch object.  */", file=f)
     print(file=f)
+    print("#include <vector>",file=f)
     #
     # The struct definition body.
     #
@@ -137,6 +138,8 @@ with open("gdbarch.c", "w") as f:
     print("  auto_obstack obstack;", file=f)
     print("  /* Registry.  */", file=f)
     print("  registry<gdbarch> registry_fields;", file=f)
+    print("  /* list of frame unwinders.  */", file=f)
+    print("  std::vector<const frame_unwind *> unwinders;", file=f)
     print(file=f)
     print("  /* basic architectural information.  */", file=f)
     for c in filter(info, components):

gdb/h8300-tdep.c

@@ -500,15 +500,16 @@ h8300_frame_prev_register (frame_info_ptr this_frame, void **this_cache,
   return frame_unwind_got_register (this_frame, regnum, regnum);
 }
 
-static const struct frame_unwind h8300_frame_unwind = {
+static const struct frame_unwind_legacy h8300_frame_unwind (
   "h8300 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   h8300_frame_this_id,
   h8300_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 static CORE_ADDR
 h8300_frame_base_address (frame_info_ptr this_frame, void **this_cache)

gdb/hppa-linux-tdep.c

@@ -308,15 +308,16 @@ hppa_linux_sigtramp_frame_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind hppa_linux_sigtramp_frame_unwind = {
+static const struct frame_unwind_legacy hppa_linux_sigtramp_frame_unwind (
   "hppa linux sigtramp",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   hppa_linux_sigtramp_frame_this_id,
   hppa_linux_sigtramp_frame_prev_register,
   NULL,
   hppa_linux_sigtramp_frame_sniffer
-};
+);
 
 /* Attempt to find (and return) the global pointer for the given
    function.

gdb/hppa-tdep.c

@@ -2283,16 +2283,16 @@ hppa_frame_unwind_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind hppa_frame_unwind =
+static const struct frame_unwind_legacy hppa_frame_unwind (
-{
   "hppa unwind table",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   hppa_frame_this_id,
   hppa_frame_prev_register,
   NULL,
   hppa_frame_unwind_sniffer
-};
+);
 
 /* This is a generic fallback frame unwinder that kicks in if we fail all
    the other ones.  Normally we would expect the stub and regular unwinder
@@ -2396,16 +2396,16 @@ hppa_fallback_frame_prev_register (frame_info_ptr this_frame,
 					  info->saved_regs, regnum);
 }
 
-static const struct frame_unwind hppa_fallback_frame_unwind =
+static const struct frame_unwind_legacy hppa_fallback_frame_unwind (
-{
   "hppa prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   hppa_fallback_frame_this_id,
   hppa_fallback_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 /* Stub frames, used for all kinds of call stubs.  */
 struct hppa_stub_unwind_cache
@@ -2478,15 +2478,16 @@ hppa_stub_unwind_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind hppa_stub_frame_unwind = {
+static const struct frame_unwind_legacy hppa_stub_frame_unwind (
   "hppa stub",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   hppa_stub_frame_this_id,
   hppa_stub_frame_prev_register,
   NULL,
   hppa_stub_unwind_sniffer
-};
+);
 
 CORE_ADDR
 hppa_unwind_pc (struct gdbarch *gdbarch, frame_info_ptr next_frame)

gdb/i386-obsd-tdep.c

@@ -390,18 +390,19 @@ i386obsd_trapframe_sniffer (const struct frame_unwind *self,
 		   || startswith (name, "Xsoft")));
 }
 
-static const struct frame_unwind i386obsd_trapframe_unwind = {
+static const struct frame_unwind_legacy i386obsd_trapframe_unwind (
   "i386 openbsd trap",
   /* FIXME: kettenis/20051219: This really is more like an interrupt
      frame, but SIGTRAMP_FRAME would print <signal handler called>,
      which really is not what we want here.  */
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   i386obsd_trapframe_this_id,
   i386obsd_trapframe_prev_register,
   NULL,
   i386obsd_trapframe_sniffer
-};
+);
 
 
 static void 

gdb/i386-tdep.c

@@ -2196,16 +2196,16 @@ i386_frame_prev_register (frame_info_ptr this_frame, void **this_cache,
   return frame_unwind_got_register (this_frame, regnum, regnum);
 }
 
-static const struct frame_unwind i386_frame_unwind =
+static const struct frame_unwind_legacy i386_frame_unwind (
-{
   "i386 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   i386_frame_unwind_stop_reason,
   i386_frame_this_id,
   i386_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 /* Normal frames, but in a function epilogue.  */
 
@@ -2351,27 +2351,27 @@ i386_epilogue_frame_prev_register (frame_info_ptr this_frame,
   return i386_frame_prev_register (this_frame, this_cache, regnum);
 }
 
-static const struct frame_unwind i386_epilogue_override_frame_unwind =
+static const struct frame_unwind_legacy i386_epilogue_override_frame_unwind (
-{
   "i386 epilogue override",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   i386_epilogue_frame_unwind_stop_reason,
   i386_epilogue_frame_this_id,
   i386_epilogue_frame_prev_register,
   NULL,
   i386_epilogue_override_frame_sniffer
-};
+);
 
-static const struct frame_unwind i386_epilogue_frame_unwind =
+static const struct frame_unwind_legacy i386_epilogue_frame_unwind (
-{
   "i386 epilogue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   i386_epilogue_frame_unwind_stop_reason,
   i386_epilogue_frame_this_id,
   i386_epilogue_frame_prev_register,
   NULL,
   i386_epilogue_frame_sniffer
-};
+);
 
 
 /* Stack-based trampolines.  */
@@ -2444,16 +2444,16 @@ i386_stack_tramp_frame_sniffer (const struct frame_unwind *self,
     return 0;
 }
 
-static const struct frame_unwind i386_stack_tramp_frame_unwind =
+static const struct frame_unwind_legacy i386_stack_tramp_frame_unwind (
-{
   "i386 stack tramp",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   i386_epilogue_frame_unwind_stop_reason,
   i386_epilogue_frame_this_id,
   i386_epilogue_frame_prev_register,
   NULL,
   i386_stack_tramp_frame_sniffer
-};
+);
 
 /* Generate a bytecode expression to get the value of the saved PC.  */
 
@@ -2593,16 +2593,16 @@ i386_sigtramp_frame_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind i386_sigtramp_frame_unwind =
+static const struct frame_unwind_legacy i386_sigtramp_frame_unwind (
-{
   "i386 sigtramp",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   i386_sigtramp_frame_unwind_stop_reason,
   i386_sigtramp_frame_this_id,
   i386_sigtramp_frame_prev_register,
   NULL,
   i386_sigtramp_frame_sniffer
-};
+);
 
 
 static CORE_ADDR

gdb/ia64-tdep.c

@@ -2162,16 +2162,16 @@ ia64_frame_prev_register (frame_info_ptr this_frame, void **this_cache,
     }
 }
  
-static const struct frame_unwind ia64_frame_unwind =
+static const struct frame_unwind_legacy ia64_frame_unwind (
-{
   "ia64 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   &ia64_frame_this_id,
   &ia64_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 /* Signal trampolines.  */
 
@@ -2351,16 +2351,16 @@ ia64_sigtramp_frame_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind ia64_sigtramp_frame_unwind =
+static const struct frame_unwind_legacy ia64_sigtramp_frame_unwind (
-{
   "ia64 sigtramp",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   ia64_sigtramp_frame_this_id,
   ia64_sigtramp_frame_prev_register,
   NULL,
   ia64_sigtramp_frame_sniffer
-};
+);
 
 
 
@@ -3011,17 +3011,17 @@ ia64_libunwind_frame_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind ia64_libunwind_frame_unwind =
+static const struct frame_unwind_legacy ia64_libunwind_frame_unwind (
-{
   "ia64 libunwind",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   ia64_libunwind_frame_this_id,
   ia64_libunwind_frame_prev_register,
   NULL,
   ia64_libunwind_frame_sniffer,
   libunwind_frame_dealloc_cache
-};
+);
 
 static void
 ia64_libunwind_sigtramp_frame_this_id (frame_info_ptr this_frame,
@@ -3100,16 +3100,16 @@ ia64_libunwind_sigtramp_frame_sniffer (const struct frame_unwind *self,
     return ia64_sigtramp_frame_sniffer (self, this_frame, this_cache);
 }
 
-static const struct frame_unwind ia64_libunwind_sigtramp_frame_unwind =
+static const struct frame_unwind_legacy ia64_libunwind_sigtramp_frame_unwind (
-{
   "ia64 libunwind sigtramp",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   ia64_libunwind_sigtramp_frame_this_id,
   ia64_libunwind_sigtramp_frame_prev_register,
   NULL,
   ia64_libunwind_sigtramp_frame_sniffer
-};
+);
 
 /* Set of libunwind callback acccessor functions.  */
 unw_accessors_t ia64_unw_accessors =

gdb/inline-frame.c

@@ -265,15 +265,16 @@ inline_frame_sniffer (const struct frame_unwind *self,
   return 1;
 }
 
-const struct frame_unwind inline_frame_unwind = {
+const struct frame_unwind_legacy inline_frame_unwind (
   "inline",
   INLINE_FRAME,
+  FRAME_UNWIND_GDB,
   default_frame_unwind_stop_reason,
   inline_frame_this_id,
   inline_frame_prev_register,
   NULL,
   inline_frame_sniffer
-};
+);
 
 /* Return non-zero if BLOCK, an inlined function block containing PC,
    has a group of contiguous instructions starting at PC (but not

gdb/inline-frame.h

@@ -27,7 +27,7 @@ struct process_stratum_target;
 
 /* The inline frame unwinder.  */
 
-extern const struct frame_unwind inline_frame_unwind;
+extern const struct frame_unwind_legacy inline_frame_unwind;
 
 /* Skip all inlined functions whose call sites are at the current PC.
 

gdb/iq2000-tdep.c

@@ -424,15 +424,16 @@ iq2000_frame_this_id (frame_info_ptr this_frame, void **this_cache,
   *this_id = frame_id_build (cache->saved_sp, cache->pc);
 }
 
-static const struct frame_unwind iq2000_frame_unwind = {
+static const struct frame_unwind_legacy iq2000_frame_unwind (
   "iq2000 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   iq2000_frame_this_id,
   iq2000_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 static CORE_ADDR
 iq2000_frame_base_address (frame_info_ptr this_frame, void **this_cache)

gdb/jit.c

@@ -1104,17 +1104,17 @@ jit_frame_prev_register (frame_info_ptr this_frame, void **cache, int reg)
 /* Relay everything back to the unwinder registered by the JIT debug
    info reader.*/
 
-static const struct frame_unwind jit_frame_unwind =
+static const struct frame_unwind_legacy jit_frame_unwind (
-{
   "jit",
   NORMAL_FRAME,
+  FRAME_UNWIND_EXTENSION,
   default_frame_unwind_stop_reason,
   jit_frame_this_id,
   jit_frame_prev_register,
   NULL,
   jit_frame_sniffer,
   jit_dealloc_cache
-};
+);
 
 
 /* This is the information that is stored at jit_gdbarch_data for each

gdb/lm32-tdep.c

@@ -447,15 +447,16 @@ lm32_frame_prev_register (frame_info_ptr this_frame,
   return trad_frame_get_prev_register (this_frame, info->saved_regs, regnum);
 }
 
-static const struct frame_unwind lm32_frame_unwind = {
+static const struct frame_unwind_legacy lm32_frame_unwind (
   "lm32 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   lm32_frame_this_id,
   lm32_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 static CORE_ADDR
 lm32_frame_base_address (frame_info_ptr this_frame, void **this_cache)

gdb/loongarch-tdep.c

@@ -450,17 +450,18 @@ loongarch_frame_prev_register (frame_info_ptr this_frame,
   return trad_frame_get_register (info, this_frame, regnum);
 }
 
-static const struct frame_unwind loongarch_frame_unwind = {
+static const struct frame_unwind_legacy loongarch_frame_unwind (
   "loongarch prologue",
   /*.type	   =*/NORMAL_FRAME,
+  /*.unwinder_class=*/FRAME_UNWIND_ARCH,
   /*.stop_reason   =*/default_frame_unwind_stop_reason,
   /*.this_id	   =*/loongarch_frame_this_id,
   /*.prev_register =*/loongarch_frame_prev_register,
   /*.unwind_data   =*/nullptr,
   /*.sniffer	   =*/default_frame_sniffer,
   /*.dealloc_cache =*/nullptr,
-  /*.prev_arch	   =*/nullptr,
+  /*.prev_arch	   =*/nullptr
-};
+);
 
 /* Write the contents of buffer VAL into the general-purpose argument
    register defined by GAR in REGCACHE.  GAR indicates the available

gdb/m32c-tdep.c

@@ -1955,15 +1955,16 @@ m32c_prev_register (frame_info_ptr this_frame,
 }
 
 
-static const struct frame_unwind m32c_unwind = {
+static const struct frame_unwind_legacy m32c_unwind (
   "m32c prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   m32c_this_id,
   m32c_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 
 /* Inferior calls.  */

gdb/m32r-linux-tdep.c

@@ -301,15 +301,16 @@ m32r_linux_sigtramp_frame_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind m32r_linux_sigtramp_frame_unwind = {
+static const struct frame_unwind_legacy m32r_linux_sigtramp_frame_unwind (
   "m32r linux sigtramp",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   m32r_linux_sigtramp_frame_this_id,
   m32r_linux_sigtramp_frame_prev_register,
   NULL,
   m32r_linux_sigtramp_frame_sniffer
-};
+);
 
 /* Mapping between the registers in `struct pt_regs'
    format and GDB's register array layout.  */

gdb/m32r-tdep.c

@@ -831,15 +831,16 @@ m32r_frame_prev_register (frame_info_ptr this_frame,
   return trad_frame_get_prev_register (this_frame, info->saved_regs, regnum);
 }
 
-static const struct frame_unwind m32r_frame_unwind = {
+static const struct frame_unwind_legacy m32r_frame_unwind (
   "m32r prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   m32r_frame_this_id,
   m32r_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 static CORE_ADDR
 m32r_frame_base_address (frame_info_ptr this_frame, void **this_cache)

gdb/m68hc11-tdep.c

@@ -936,15 +936,16 @@ m68hc11_frame_prev_register (frame_info_ptr this_frame,
   return value;
 }
 
-static const struct frame_unwind m68hc11_frame_unwind = {
+static const struct frame_unwind_legacy m68hc11_frame_unwind (
   "m68hc11 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   m68hc11_frame_this_id,
   m68hc11_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 static CORE_ADDR
 m68hc11_frame_base_address (frame_info_ptr this_frame, void **this_cache)

gdb/m68k-linux-tdep.c

@@ -314,16 +314,16 @@ m68k_linux_sigtramp_frame_sniffer (const struct frame_unwind *self,
   return m68k_linux_pc_in_sigtramp (this_frame);
 }
 
-static const struct frame_unwind m68k_linux_sigtramp_frame_unwind =
+static const struct frame_unwind_legacy m68k_linux_sigtramp_frame_unwind (
-{
   "m68k linux sigtramp",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   m68k_linux_sigtramp_frame_this_id,
   m68k_linux_sigtramp_frame_prev_register,
   NULL,
   m68k_linux_sigtramp_frame_sniffer
-};
+);
 
 /* Register maps for supply/collect regset functions.  */
 

gdb/m68k-tdep.c

@@ -1007,16 +1007,16 @@ m68k_frame_prev_register (frame_info_ptr this_frame, void **this_cache,
   return frame_unwind_got_register (this_frame, regnum, regnum);
 }
 
-static const struct frame_unwind m68k_frame_unwind =
+static const struct frame_unwind_legacy m68k_frame_unwind (
-{
   "m68k prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   m68k_frame_this_id,
   m68k_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 static CORE_ADDR
 m68k_frame_base_address (frame_info_ptr this_frame, void **this_cache)

gdb/mep-tdep.c

@@ -2061,15 +2061,16 @@ mep_frame_prev_register (frame_info_ptr this_frame,
 }
 
 
-static const struct frame_unwind mep_frame_unwind = {
+static const struct frame_unwind_legacy mep_frame_unwind (
   "mep prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   mep_frame_this_id,
   mep_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 
 /* Return values.  */

gdb/microblaze-tdep.c

@@ -478,16 +478,16 @@ microblaze_frame_prev_register (frame_info_ptr this_frame,
 
 }
 
-static const struct frame_unwind microblaze_frame_unwind =
+static const struct frame_unwind_legacy microblaze_frame_unwind (
-{
   "microblaze prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   microblaze_frame_this_id,
   microblaze_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 static CORE_ADDR
 microblaze_frame_base_address (frame_info_ptr next_frame,

gdb/mips-sde-tdep.c

@@ -161,16 +161,16 @@ mips_sde_frame_sniffer (const struct frame_unwind *self,
 
 /* Data structure for the SDE frame unwinder.  */
 
-static const struct frame_unwind mips_sde_frame_unwind =
+static const struct frame_unwind_legacy mips_sde_frame_unwind (
-{
   "mips sde sigtramp",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   mips_sde_frame_this_id,
   mips_sde_frame_prev_register,
   NULL,
   mips_sde_frame_sniffer
-};
+);
 
 /* Implement the this_base, this_locals, and this_args hooks
    for the normal unwinder.  */

gdb/mips-tdep.c

@@ -2929,16 +2929,16 @@ mips_insn16_frame_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind mips_insn16_frame_unwind =
+static const struct frame_unwind_legacy mips_insn16_frame_unwind (
-{
   "mips insn16 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   mips_insn16_frame_this_id,
   mips_insn16_frame_prev_register,
   NULL,
   mips_insn16_frame_sniffer
-};
+);
 
 static CORE_ADDR
 mips_insn16_frame_base_address (frame_info_ptr this_frame,
@@ -3365,16 +3365,16 @@ mips_micro_frame_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind mips_micro_frame_unwind =
+static const struct frame_unwind_legacy mips_micro_frame_unwind (
-{
   "mips micro prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   mips_micro_frame_this_id,
   mips_micro_frame_prev_register,
   NULL,
   mips_micro_frame_sniffer
-};
+);
 
 static CORE_ADDR
 mips_micro_frame_base_address (frame_info_ptr this_frame,
@@ -3744,16 +3744,16 @@ mips_insn32_frame_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind mips_insn32_frame_unwind =
+static const struct frame_unwind_legacy mips_insn32_frame_unwind (
-{
   "mips insn32 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   mips_insn32_frame_this_id,
   mips_insn32_frame_prev_register,
   NULL,
   mips_insn32_frame_sniffer
-};
+);
 
 static CORE_ADDR
 mips_insn32_frame_base_address (frame_info_ptr this_frame,
@@ -3861,16 +3861,16 @@ mips_stub_frame_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind mips_stub_frame_unwind =
+static const struct frame_unwind_legacy mips_stub_frame_unwind (
-{
   "mips stub",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   mips_stub_frame_this_id,
   mips_stub_frame_prev_register,
   NULL,
   mips_stub_frame_sniffer
-};
+);
 
 static CORE_ADDR
 mips_stub_frame_base_address (frame_info_ptr this_frame,

gdb/mn10300-tdep.c

@@ -1127,15 +1127,16 @@ mn10300_frame_prev_register (frame_info_ptr this_frame,
   return frame_unwind_got_register (this_frame, regnum, regnum);
 }
 
-static const struct frame_unwind mn10300_frame_unwind = {
+static const struct frame_unwind_legacy mn10300_frame_unwind (
   "mn10300 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   mn10300_frame_this_id, 
   mn10300_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 static void
 mn10300_frame_unwind_init (struct gdbarch *gdbarch)

gdb/moxie-tdep.c

@@ -585,15 +585,16 @@ moxie_frame_prev_register (frame_info_ptr this_frame,
   return frame_unwind_got_register (this_frame, regnum, regnum);
 }
 
-static const struct frame_unwind moxie_frame_unwind = {
+static const struct frame_unwind_legacy moxie_frame_unwind (
   "moxie prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   moxie_frame_this_id,
   moxie_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 /* Return the base address of this_frame.  */
 

gdb/msp430-tdep.c

@@ -542,15 +542,16 @@ msp430_prev_register (frame_info_ptr this_frame,
     return frame_unwind_got_register (this_frame, regnum, regnum);
 }
 
-static const struct frame_unwind msp430_unwind = {
+static const struct frame_unwind_legacy msp430_unwind (
   "msp430 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   msp430_this_id,
   msp430_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 /* Implement the "dwarf2_reg_to_regnum" gdbarch method.  */
 

gdb/nds32-tdep.c

@@ -988,16 +988,16 @@ nds32_frame_prev_register (frame_info_ptr this_frame, void **this_cache,
   return frame_unwind_got_register (this_frame, regnum, regnum);
 }
 
-static const struct frame_unwind nds32_frame_unwind =
+static const struct frame_unwind_legacy nds32_frame_unwind (
-{
   "nds32 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   nds32_frame_this_id,
   nds32_frame_prev_register,
   NULL,
-  default_frame_sniffer,
+  default_frame_sniffer
-};
+);
 
 /* Return the frame base address of *THIS_FRAME.  */
 
@@ -1372,16 +1372,16 @@ nds32_epilogue_frame_prev_register (frame_info_ptr this_frame,
   return frame_unwind_got_register (this_frame, regnum, regnum);
 }
 
-static const struct frame_unwind nds32_epilogue_frame_unwind =
+static const struct frame_unwind_legacy nds32_epilogue_frame_unwind (
-{
   "nds32 epilogue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   nds32_epilogue_frame_this_id,
   nds32_epilogue_frame_prev_register,
   NULL,
   nds32_epilogue_frame_sniffer
-};
+);
 
 
 /* Floating type and struct type that has only one floating type member

gdb/nios2-tdep.c

@@ -1977,16 +1977,16 @@ nios2_frame_base_address (frame_info_ptr this_frame, void **this_cache)
 /* Data structures for the normal prologue-analysis-based
    unwinder.  */
 
-static const struct frame_unwind nios2_frame_unwind =
+static const struct frame_unwind_legacy nios2_frame_unwind (
-{
   "nios2 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   nios2_frame_this_id,
   nios2_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 static const struct frame_base nios2_frame_base =
 {
@@ -2078,16 +2078,16 @@ nios2_stub_frame_sniffer (const struct frame_unwind *self,
 
 /* Define the data structures for the stub unwinder.  */
 
-static const struct frame_unwind nios2_stub_frame_unwind =
+static const struct frame_unwind_legacy nios2_stub_frame_unwind (
-{
   "nios2 stub",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   nios2_stub_frame_this_id,
   nios2_stub_frame_prev_register,
   NULL,
   nios2_stub_frame_sniffer
-};
+);
 
 
 

gdb/or1k-tdep.c

@@ -1125,16 +1125,17 @@ or1k_frame_prev_register (frame_info_ptr this_frame,
 
 /* Data structures for the normal prologue-analysis-based unwinder.  */
 
-static const struct frame_unwind or1k_frame_unwind = {
+static const struct frame_unwind_legacy or1k_frame_unwind (
   "or1k prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   or1k_frame_this_id,
   or1k_frame_prev_register,
   NULL,
   default_frame_sniffer,
-  NULL,
+  NULL
-};
+);
 
 /* Architecture initialization for OpenRISC 1000.  */
 

gdb/ppc-fbsd-tdep.c

@@ -262,15 +262,16 @@ ppcfbsd_sigtramp_frame_prev_register (frame_info_ptr this_frame,
   return trad_frame_get_register (cache, this_frame, regnum);
 }
 
-static const struct frame_unwind ppcfbsd_sigtramp_frame_unwind = {
+static const struct frame_unwind_legacy ppcfbsd_sigtramp_frame_unwind (
   "ppc freebsd sigtramp",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   ppcfbsd_sigtramp_frame_this_id,
   ppcfbsd_sigtramp_frame_prev_register,
   NULL,
   ppcfbsd_sigtramp_frame_sniffer
-};
+);
 
 static enum return_value_convention
 ppcfbsd_return_value (struct gdbarch *gdbarch, struct value *function,

gdb/ppc-obsd-tdep.c

@@ -231,15 +231,16 @@ ppcobsd_sigtramp_frame_prev_register (frame_info_ptr this_frame,
   return trad_frame_get_register (cache, this_frame, regnum);
 }
 
-static const struct frame_unwind ppcobsd_sigtramp_frame_unwind = {
+static const struct frame_unwind_legacy ppcobsd_sigtramp_frame_unwind (
   "ppc openbsd sigtramp",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   ppcobsd_sigtramp_frame_this_id,
   ppcobsd_sigtramp_frame_prev_register,
   NULL,
   ppcobsd_sigtramp_frame_sniffer
-};
+);
 
 
 static void

gdb/python/py-unwind.c

@@ -807,7 +807,7 @@ pyuw_sniffer (const struct frame_unwind *self, frame_info_ptr this_frame,
 {
   PYUW_SCOPED_DEBUG_ENTER_EXIT;
 
-  struct gdbarch *gdbarch = (struct gdbarch *) (self->unwind_data);
+  struct gdbarch *gdbarch = (struct gdbarch *) (self->unwind_data ());
   cached_frame_info *cached_frame;
 
   gdbpy_enter enter_py (gdbarch);
@@ -948,6 +948,41 @@ struct pyuw_gdbarch_data_type
 
 static const registry<gdbarch>::key<pyuw_gdbarch_data_type> pyuw_gdbarch_data;
 
+/* Class for frame unwinders registered by the Python architecture callback.  */
+class frame_unwind_python : public frame_unwind
+{
+public:
+  frame_unwind_python (const struct frame_data *newarch)
+    : frame_unwind ("python", NORMAL_FRAME, FRAME_UNWIND_EXTENSION, newarch)
+  { }
+
+  /* No need to override stop_reason, we want the default.  */
+
+  int sniffer (const frame_unwind *self, frame_info_ptr this_frame,
+		void **this_prologue_cache) const override
+  {
+    return pyuw_sniffer (self, this_frame, this_prologue_cache);
+  }
+
+  void this_id (frame_info_ptr this_frame, void **this_prologue_cache,
+		struct frame_id *id) const override
+  {
+    pyuw_this_id (this_frame, this_prologue_cache, id);
+  }
+
+  struct value *prev_register (frame_info_ptr this_frame,
+			       void **this_prologue_cache,
+			       int regnum) const override
+  {
+      return pyuw_prev_register (this_frame, this_prologue_cache, regnum);
+  }
+
+  void dealloc_cache (frame_info *self, void *this_cache) const override
+  {
+      pyuw_dealloc_cache (self, this_cache);
+  }
+};
+
 /* New inferior architecture callback: register the Python unwinders
    intermediary.  */
 
@@ -961,16 +996,9 @@ pyuw_on_new_gdbarch (gdbarch *newarch)
   if (!data->unwinder_registered)
     {
       struct frame_unwind *unwinder
-	  = GDBARCH_OBSTACK_ZALLOC (newarch, struct frame_unwind);
+	  = obstack_new<frame_unwind_python>
+	    (gdbarch_obstack(newarch), (const struct frame_data *) newarch);
 
-      unwinder->name = "python";
-      unwinder->type = NORMAL_FRAME;
-      unwinder->stop_reason = default_frame_unwind_stop_reason;
-      unwinder->this_id = pyuw_this_id;
-      unwinder->prev_register = pyuw_prev_register;
-      unwinder->unwind_data = (const struct frame_data *) newarch;
-      unwinder->sniffer = pyuw_sniffer;
-      unwinder->dealloc_cache = pyuw_dealloc_cache;
       frame_unwind_prepend_unwinder (newarch, unwinder);
       data->unwinder_registered = 1;
     }

gdb/record-btrace.c

@@ -1894,29 +1894,29 @@ record_btrace_frame_dealloc_cache (frame_info *self, void *this_cache)
    Therefore this unwinder reports any possibly unwound registers as
    <unavailable>.  */
 
-const struct frame_unwind record_btrace_frame_unwind =
+const struct frame_unwind_legacy record_btrace_frame_unwind (
-{
   "record-btrace",
   NORMAL_FRAME,
+  FRAME_UNWIND_GDB,
   record_btrace_frame_unwind_stop_reason,
   record_btrace_frame_this_id,
   record_btrace_frame_prev_register,
   NULL,
   record_btrace_frame_sniffer,
   record_btrace_frame_dealloc_cache
-};
+);
 
-const struct frame_unwind record_btrace_tailcall_frame_unwind =
+const struct frame_unwind_legacy record_btrace_tailcall_frame_unwind (
-{
   "record-btrace tailcall",
   TAILCALL_FRAME,
+  FRAME_UNWIND_GDB,
   record_btrace_frame_unwind_stop_reason,
   record_btrace_frame_this_id,
   record_btrace_frame_prev_register,
   NULL,
   record_btrace_tailcall_frame_sniffer,
   record_btrace_frame_dealloc_cache
-};
+);
 
 /* Implement the get_unwinder method.  */
 

gdb/record.h

@@ -36,8 +36,8 @@ extern struct cmd_list_element *show_record_cmdlist;
 extern struct cmd_list_element *info_record_cmdlist;
 
 /* Unwinders for some record targets.  */
-extern const struct frame_unwind record_btrace_frame_unwind;
+extern const struct frame_unwind_legacy record_btrace_frame_unwind;
-extern const struct frame_unwind record_btrace_tailcall_frame_unwind;
+extern const struct frame_unwind_legacy record_btrace_tailcall_frame_unwind;
 
 /* A list of different recording methods.  */
 enum record_method

gdb/riscv-tdep.c

@@ -3901,18 +3901,18 @@ riscv_frame_prev_register (frame_info_ptr this_frame,
    are the fallback unwinder (DWARF unwinder is used first), we use the
    default frame sniffer, which always accepts the frame.  */
 
-static const struct frame_unwind riscv_frame_unwind =
+static const struct frame_unwind_legacy riscv_frame_unwind (
-{
   /*.name          =*/ "riscv prologue",
   /*.type          =*/ NORMAL_FRAME,
+  /*.unwinder_class=*/FRAME_UNWIND_ARCH,
   /*.stop_reason   =*/ default_frame_unwind_stop_reason,
   /*.this_id       =*/ riscv_frame_this_id,
   /*.prev_register =*/ riscv_frame_prev_register,
   /*.unwind_data   =*/ NULL,
   /*.sniffer       =*/ default_frame_sniffer,
   /*.dealloc_cache =*/ NULL,
-  /*.prev_arch     =*/ NULL,
+  /*.prev_arch     =*/ NULL
-};
+);
 
 /* Extract a set of required target features out of ABFD.  If ABFD is
    nullptr then a RISCV_GDBARCH_FEATURES is returned in its default state.  */

gdb/rl78-tdep.c

@@ -1183,16 +1183,16 @@ rl78_prev_register (frame_info_ptr this_frame,
     return frame_unwind_got_register (this_frame, regnum, regnum);
 }
 
-static const struct frame_unwind rl78_unwind =
+static const struct frame_unwind_legacy rl78_unwind (
-{
   "rl78 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   rl78_this_id,
   rl78_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 /* Implement the "dwarf_reg_to_regnum" gdbarch method.  */
 

gdb/rs6000-aix-tdep.c

@@ -328,15 +328,16 @@ aix_sighandle_frame_sniffer (const struct frame_unwind *self,
 
 /* AIX signal handler frame unwinder */
 
-static const struct frame_unwind aix_sighandle_frame_unwind = {
+static const struct frame_unwind_legacy aix_sighandle_frame_unwind (
   "rs6000 aix sighandle",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   aix_sighandle_frame_this_id,
   aix_sighandle_frame_prev_register,
   NULL,
   aix_sighandle_frame_sniffer
-};
+);
 
 /* Core file support.  */
 

gdb/rs6000-tdep.c

@@ -3838,16 +3838,16 @@ rs6000_frame_prev_register (frame_info_ptr this_frame,
   return trad_frame_get_prev_register (this_frame, info->saved_regs, regnum);
 }
 
-static const struct frame_unwind rs6000_frame_unwind =
+static const struct frame_unwind_legacy rs6000_frame_unwind (
-{
   "rs6000 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   rs6000_frame_this_id,
   rs6000_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 /* Allocate and initialize a frame cache for an epilogue frame.
    SP is restored and prev-PC is stored in LR.  */
@@ -3979,15 +3979,15 @@ rs6000_epilogue_frame_sniffer (const struct frame_unwind *self,
 /* Frame unwinder for epilogue frame.  This is required for reverse step-over
    a function without debug information.  */
 
-static const struct frame_unwind rs6000_epilogue_frame_unwind =
+static const struct frame_unwind_legacy rs6000_epilogue_frame_unwind (
-{
   "rs6000 epilogue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   rs6000_epilogue_frame_this_id, rs6000_epilogue_frame_prev_register,
   NULL,
   rs6000_epilogue_frame_sniffer
-};
+);
 
 
 static CORE_ADDR

gdb/rx-tdep.c

@@ -631,29 +631,31 @@ rx_exception_sniffer (const struct frame_unwind *self,
 /* Data structure for normal code using instruction-based prologue
    analyzer.  */
 
-static const struct frame_unwind rx_frame_unwind = {
+static const struct frame_unwind_legacy rx_frame_unwind (
   "rx prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   rx_frame_this_id,
   rx_frame_prev_register,
   NULL,
   rx_frame_sniffer
-};
+);
 
 /* Data structure for exception code using instruction-based prologue
    analyzer.  */
 
-static const struct frame_unwind rx_exception_unwind = {
+static const struct frame_unwind_legacy rx_exception_unwind (
   "rx exception",
   /* SIGTRAMP_FRAME could be used here, but backtraces are less informative.  */
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   rx_frame_this_id,
   rx_frame_prev_register,
   NULL,
   rx_exception_sniffer
-};
+);
 
 /* Implement the "push_dummy_call" gdbarch method.  */
 static CORE_ADDR

gdb/s12z-tdep.c

@@ -442,16 +442,17 @@ s12z_frame_prev_register (frame_info_ptr this_frame,
 }
 
 /* Data structures for the normal prologue-analysis-based unwinder.  */
-static const struct frame_unwind s12z_frame_unwind = {
+static const struct frame_unwind_legacy s12z_frame_unwind (
   "s12z prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   s12z_frame_this_id,
   s12z_frame_prev_register,
   NULL,
   default_frame_sniffer,
-  NULL,
+  NULL
-};
+);
 
 
 constexpr gdb_byte s12z_break_insn[] = {0x00};

gdb/s390-linux-tdep.c

@@ -542,15 +542,16 @@ s390_sigtramp_frame_sniffer (const struct frame_unwind *self,
 
 /* S390 sigtramp frame unwinder.  */
 
-static const struct frame_unwind s390_sigtramp_frame_unwind = {
+static const struct frame_unwind_legacy s390_sigtramp_frame_unwind (
   "s390 linux sigtramp",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   s390_sigtramp_frame_this_id,
   s390_sigtramp_frame_prev_register,
   NULL,
   s390_sigtramp_frame_sniffer
-};
+);
 
 /* Syscall handling.  */
 

gdb/s390-tdep.c

@@ -2646,15 +2646,16 @@ s390_frame_prev_register (frame_info_ptr this_frame,
 
 /* Default S390 frame unwinder.  */
 
-static const struct frame_unwind s390_frame_unwind = {
+static const struct frame_unwind_legacy s390_frame_unwind (
   "s390 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   s390_frame_this_id,
   s390_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 /* Code stubs and their stack frames.  For things like PLTs and NULL
    function calls (where there is no true frame and the return address
@@ -2740,15 +2741,16 @@ s390_stub_frame_sniffer (const struct frame_unwind *self,
 
 /* S390 stub frame unwinder.  */
 
-static const struct frame_unwind s390_stub_frame_unwind = {
+static const struct frame_unwind_legacy s390_stub_frame_unwind (
   "s390 stub",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   s390_stub_frame_this_id,
   s390_stub_frame_prev_register,
   NULL,
   s390_stub_frame_sniffer
-};
+);
 
 /* Frame base handling.  */
 

gdb/sentinel-frame.c

@@ -79,15 +79,15 @@ sentinel_frame_prev_arch (frame_info_ptr this_frame,
   return cache->regcache->arch ();
 }
 
-const struct frame_unwind sentinel_frame_unwind =
+const struct frame_unwind_legacy sentinel_frame_unwind (
-{
   "sentinel",
   SENTINEL_FRAME,
+  FRAME_UNWIND_GDB,
   default_frame_unwind_stop_reason,
   sentinel_frame_this_id,
   sentinel_frame_prev_register,
   NULL,
   NULL,
   NULL,
-  sentinel_frame_prev_arch,
+  sentinel_frame_prev_arch
-};
+);

gdb/sentinel-frame.h

@@ -34,6 +34,6 @@ extern void *sentinel_frame_cache (struct regcache *regcache);
 
 /* At present there is only one type of sentinel frame.  */
 
-extern const struct frame_unwind sentinel_frame_unwind;
+extern const struct frame_unwind_legacy sentinel_frame_unwind;
 
 #endif /* !defined (SENTINEL_FRAME_H)  */

gdb/sh-tdep.c

@@ -1929,15 +1929,16 @@ sh_frame_this_id (frame_info_ptr this_frame, void **this_cache,
   *this_id = frame_id_build (cache->saved_sp, cache->pc);
 }
 
-static const struct frame_unwind sh_frame_unwind = {
+static const struct frame_unwind_legacy sh_frame_unwind (
   "sh prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   sh_frame_this_id,
   sh_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 static CORE_ADDR
 sh_frame_base_address (frame_info_ptr this_frame, void **this_cache)
@@ -1995,16 +1996,16 @@ sh_stub_unwind_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind sh_stub_unwind =
+static const struct frame_unwind_legacy sh_stub_unwind (
-{
   "sh stub",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   sh_stub_this_id,
   sh_frame_prev_register,
   NULL,
   sh_stub_unwind_sniffer
-};
+);
 
 /* Implement the stack_frame_destroyed_p gdbarch method.
 

gdb/sparc-netbsd-tdep.c

@@ -249,16 +249,16 @@ sparc32nbsd_sigcontext_frame_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind sparc32nbsd_sigcontext_frame_unwind =
+static const struct frame_unwind_legacy sparc32nbsd_sigcontext_frame_unwind (
-{
   "sparc32 netbsd sigcontext",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   sparc32nbsd_sigcontext_frame_this_id,
   sparc32nbsd_sigcontext_frame_prev_register,
   NULL,
   sparc32nbsd_sigcontext_frame_sniffer
-};
+);
 
 /* Return the address of a system call's alternative return
    address.  */

gdb/sparc-obsd-tdep.c

@@ -134,16 +134,16 @@ sparc32obsd_sigtramp_frame_sniffer (const struct frame_unwind *self,
 
   return 0;
 }
-static const struct frame_unwind sparc32obsd_sigtramp_frame_unwind =
+static const struct frame_unwind_legacy sparc32obsd_sigtramp_frame_unwind (
-{
   "sparc32 openbsd sigtramp",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   sparc32obsd_sigtramp_frame_this_id,
   sparc32obsd_sigtramp_frame_prev_register,
   NULL,
   sparc32obsd_sigtramp_frame_sniffer
-};
+);
 
 
 

gdb/sparc-sol2-tdep.c

@@ -180,16 +180,16 @@ sparc32_sol2_sigtramp_frame_sniffer (const struct frame_unwind *self,
   return sol2_sigtramp_p (this_frame);
 }
 
-static const struct frame_unwind sparc32_sol2_sigtramp_frame_unwind =
+static const struct frame_unwind_legacy sparc32_sol2_sigtramp_frame_unwind (
-{
   "sparc32 solaris sigtramp",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   sparc32_sol2_sigtramp_frame_this_id,
   sparc32_sol2_sigtramp_frame_prev_register,
   NULL,
   sparc32_sol2_sigtramp_frame_sniffer
-};
+);
 
 
 

gdb/sparc-tdep.c

@@ -1346,16 +1346,16 @@ sparc32_frame_prev_register (frame_info_ptr this_frame,
   return frame_unwind_got_register (this_frame, regnum, regnum);
 }
 
-static const struct frame_unwind sparc32_frame_unwind =
+static const struct frame_unwind_legacy sparc32_frame_unwind (
-{
   "sparc32 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   sparc32_frame_this_id,
   sparc32_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 
 static CORE_ADDR

gdb/sparc64-fbsd-tdep.c

@@ -197,16 +197,16 @@ sparc64fbsd_sigtramp_frame_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind sparc64fbsd_sigtramp_frame_unwind =
+static const struct frame_unwind_legacy sparc64fbsd_sigtramp_frame_unwind (
-{
   "sparc64 freebsd sigtramp",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   sparc64fbsd_sigtramp_frame_this_id,
   sparc64fbsd_sigtramp_frame_prev_register,
   NULL,
   sparc64fbsd_sigtramp_frame_sniffer
-};
+);
 
 
 static const struct regset sparc64fbsd_gregset =

gdb/sparc64-netbsd-tdep.c

@@ -223,16 +223,16 @@ sparc64nbsd_sigtramp_frame_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind sparc64nbsd_sigcontext_frame_unwind =
+static const struct frame_unwind_legacy sparc64nbsd_sigcontext_frame_unwind (
-{
   "sparc64 netbsd sigcontext",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   sparc64nbsd_sigcontext_frame_this_id,
   sparc64nbsd_sigcontext_frame_prev_register,
   NULL,
   sparc64nbsd_sigtramp_frame_sniffer
-};
+);
 
 
 static const struct regset sparc64nbsd_gregset =

gdb/sparc64-obsd-tdep.c

@@ -220,16 +220,16 @@ sparc64obsd_sigtramp_frame_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind sparc64obsd_frame_unwind =
+static const struct frame_unwind_legacy sparc64obsd_frame_unwind (
-{
   "sparc64 openbsd sigtramp",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   sparc64obsd_frame_this_id,
   sparc64obsd_frame_prev_register,
   NULL,
   sparc64obsd_sigtramp_frame_sniffer
-};
+);
 
 /* Kernel debugging support.  */
 
@@ -304,16 +304,16 @@ sparc64obsd_trapframe_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind sparc64obsd_trapframe_unwind =
+static const struct frame_unwind_legacy sparc64obsd_trapframe_unwind (
-{
   "sparc64 openbsd trap",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   sparc64obsd_trapframe_this_id,
   sparc64obsd_trapframe_prev_register,
   NULL,
   sparc64obsd_trapframe_sniffer
-};
+);
 
 
 /* Threads support.  */

gdb/sparc64-sol2-tdep.c

@@ -183,16 +183,16 @@ sparc64_sol2_sigtramp_frame_sniffer (const struct frame_unwind *self,
   return sol2_sigtramp_p (this_frame);
 }
 
-static const struct frame_unwind sparc64_sol2_sigtramp_frame_unwind =
+static const struct frame_unwind_legacy sparc64_sol2_sigtramp_frame_unwind (
-{
   "sparc64 solaris sigtramp",
   SIGTRAMP_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   sparc64_sol2_sigtramp_frame_this_id,
   sparc64_sol2_sigtramp_frame_prev_register,
   NULL,
   sparc64_sol2_sigtramp_frame_sniffer
-};
+);
 
 
 

gdb/sparc64-tdep.c

@@ -1134,16 +1134,16 @@ sparc64_frame_prev_register (frame_info_ptr this_frame, void **this_cache,
   return frame_unwind_got_register (this_frame, regnum, regnum);
 }
 
-static const struct frame_unwind sparc64_frame_unwind =
+static const struct frame_unwind_legacy sparc64_frame_unwind (
-{
   "sparc64 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   sparc64_frame_this_id,
   sparc64_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 
 static CORE_ADDR

gdb/testsuite/gdb.base/backtrace-through-cu-nodebug-caller.c

@@ -0,0 +1,28 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2005-2023 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+typedef int (*callback_t) (void);
+
+int
+caller (callback_t callback)
+{
+  /* Ensure some frame content to push away the return address.  */
+  volatile const long one = 1;
+
+  /* Modify the return value to prevent any tail-call optimization.  */
+  return (*callback) () - one;
+}

gdb/testsuite/gdb.base/backtrace-through-cu-nodebug-main.c

@@ -0,0 +1,32 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2005-2023 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+typedef int (*callback_t) (void);
+
+extern int caller (callback_t callback);
+
+int
+callback (void)
+{
+  return 1;
+}
+
+int
+main (void)
+{
+  return caller (callback);
+}

gdb/testsuite/gdb.base/backtrace-through-cu-nodebug.exp

@@ -0,0 +1,91 @@
+# Copyright 2010-2023 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Test that GDB can generate accurate backtraces even if some of the stack
+# trace goes through a function with no debug information.
+
+standard_testfile -caller.c -main.c
+set objmainfile ${testfile}-main.o
+set objcallerfile ${testfile}-caller.o
+
+# recompile the inferior with or without CFI information, then run the
+# inferior until the point where the important test starts
+# returns TRUE on an ERROR.
+proc prepare_test {has_cfi} {
+    global srcdir subdir srcfile srcfile2 objmainfile objcallerfile binfile
+    if {$has_cfi} {
+	set extension "cfi"
+	if {[gdb_compile "${srcdir}/${subdir}/${srcfile}" ${objcallerfile} \
+	     object [list {additional_flags=-fomit-frame-pointer \
+		 -funwind-tables -fasynchronous-unwind-tables}]] != "" } {
+	    untested "couldn't compile without cfi"
+	    return true
+      }
+    } else {
+	set extension "no-cfi"
+	if {[gdb_compile "${srcdir}/${subdir}/${srcfile}" ${objcallerfile} \
+	     object [list {additional_flags=-fomit-frame-pointer \
+		 -fno-unwind-tables \
+		 -fno-asynchronous-unwind-tables}]] != "" } {
+	    untested "couldn't compile with cfi"
+	    return true
+      }
+    }
+    if {[gdb_compile "${objmainfile} ${objcallerfile}" \
+	    "${binfile}-${extension}" binfile {}] != ""} {
+	untested "couldn't link object files"
+	return true
+    }
+
+    clean_restart "$binfile-${extension}"
+
+    if ![runto callback] then {
+       fail "has_cfi=$has_cfi: Can't run to callback"
+       return true
+    }
+    return false
+}
+
+if {[gdb_compile "${srcdir}/${subdir}/${srcfile2}" ${objmainfile} \
+	object {debug}] != "" } {
+    untested "couldn't compile main file"
+    return
+}
+
+if { [prepare_test false] } {
+     untested ${testfile}.exp
+} else {
+    gdb_test_multiple "bt" "verify unwinding breaks without CFI" {
+	-re -wrap " in \[?\]\[?\] .*" {
+	    # It may backtrace through some random frames even to main().
+	    pass $gdb_test_name
+	}
+	-re -wrap " in main .*" {
+	    fail $gdb_test_name
+	}
+    }
+}
+
+if { [prepare_test true] } {
+     untested ${testfile}.exp
+} else {
+
+    # #0  callback () at ...
+    # #1  0x00000000004004e9 in caller ()
+    # #2  0x00000000004004cd in main () at ...
+    gdb_test "bt" \
+	"#0 +callback \[^\r\n\]+\r\n#1 \[^\r\n\]+ in caller \[^\r\n\]+\r\n#2 \[^\r\n\]+ in main \[^\r\n\]+" \
+	"verify unwinding works for CFI without DIEs"
+}

gdb/tic6x-tdep.c

@@ -452,16 +452,16 @@ tic6x_frame_base_address (frame_info_ptr this_frame, void **this_cache)
   return info->base;
 }
 
-static const struct frame_unwind tic6x_frame_unwind =
+static const struct frame_unwind_legacy tic6x_frame_unwind (
-{
   "tic6x prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   tic6x_frame_this_id,
   tic6x_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 static const struct frame_base tic6x_frame_base =
 {
@@ -515,16 +515,16 @@ tic6x_stub_unwind_sniffer (const struct frame_unwind *self,
   return 0;
 }
 
-static const struct frame_unwind tic6x_stub_unwind =
+static const struct frame_unwind_legacy tic6x_stub_unwind (
-{
   "tic6x stub",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   tic6x_stub_this_id,
   tic6x_frame_prev_register,
   NULL,
   tic6x_stub_unwind_sniffer
-};
+);
 
 /* Return the instruction on address PC.  */
 

gdb/tilegx-tdep.c

@@ -900,16 +900,17 @@ tilegx_frame_base_address (frame_info_ptr this_frame, void **this_cache)
   return cache->base;
 }
 
-static const struct frame_unwind tilegx_frame_unwind = {
+static const struct frame_unwind_legacy tilegx_frame_unwind (
   "tilegx prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   tilegx_frame_this_id,
   tilegx_frame_prev_register,
   NULL,                        /* const struct frame_data *unwind_data  */
   default_frame_sniffer,       /* frame_sniffer_ftype *sniffer  */
   NULL                         /* frame_prev_pc_ftype *prev_pc  */
-};
+);
 
 static const struct frame_base tilegx_frame_base = {
   &tilegx_frame_unwind,

gdb/tramp-frame.c

@@ -58,6 +58,7 @@ tramp_frame_cache (frame_info_ptr this_frame,
 }
 
 static void
+__attribute__ ((__used__))
 tramp_frame_this_id (frame_info_ptr this_frame,
 		     void **this_cache,
 		     struct frame_id *this_id)
@@ -69,6 +70,7 @@ tramp_frame_this_id (frame_info_ptr this_frame,
 }
 
 static struct value *
+__attribute__ ((__used__))
 tramp_frame_prev_register (frame_info_ptr this_frame,
 			   void **this_cache,
 			   int prev_regnum)
@@ -80,6 +82,7 @@ tramp_frame_prev_register (frame_info_ptr this_frame,
 }
 
 static CORE_ADDR
+__attribute__ ((__used__))
 tramp_frame_start (const struct tramp_frame *tramp,
 		   frame_info_ptr this_frame, CORE_ADDR pc)
 {
@@ -120,11 +123,12 @@ tramp_frame_start (const struct tramp_frame *tramp,
 }
 
 static int
+__attribute__ ((__used__))
 tramp_frame_sniffer (const struct frame_unwind *self,
 		     frame_info_ptr this_frame,
 		     void **this_cache)
 {
-  const struct tramp_frame *tramp = self->unwind_data->tramp_frame;
+  const struct tramp_frame *tramp = self->unwind_data ()->tramp_frame;
   CORE_ADDR pc = get_frame_pc (this_frame);
   CORE_ADDR func;
   struct tramp_frame_cache *tramp_cache;
@@ -143,6 +147,39 @@ tramp_frame_sniffer (const struct frame_unwind *self,
   return 1;
 }
 
+class frame_unwind_trampoline : public frame_unwind {
+private:
+  frame_prev_arch_ftype *prev_arch_p;
+public:
+  frame_unwind_trampoline (enum frame_type t, const struct frame_data *d,
+			   frame_prev_arch_ftype *pa)
+    : frame_unwind ("trampoline", t, FRAME_UNWIND_GDB, d), prev_arch_p (pa)
+  { }
+
+  int sniffer(const frame_unwind *self, frame_info_ptr this_frame,
+	      void **this_prologue_cache) const override
+  {
+    return tramp_frame_sniffer (self, this_frame, this_prologue_cache);
+  }
+  void this_id (frame_info_ptr this_frame, void **this_prologue_cache,
+		struct frame_id *id) const override
+  {
+    tramp_frame_this_id (this_frame, this_prologue_cache, id);
+  }
+  struct value *prev_register (frame_info_ptr this_frame,
+			       void **this_prologue_cache,
+			       int regnum) const override
+  {
+    return tramp_frame_prev_register (this_frame, this_prologue_cache, regnum);
+  }
+
+  struct gdbarch *prev_arch (frame_info_ptr this_frame,
+			     void **this_prologue_cache) const override
+  {
+    return prev_arch_p (this_frame, this_prologue_cache);
+  }
+};
+
 void
 tramp_frame_prepend_unwinder (struct gdbarch *gdbarch,
 			      const struct tramp_frame *tramp_frame)
@@ -161,15 +198,11 @@ tramp_frame_prepend_unwinder (struct gdbarch *gdbarch,
   gdb_assert (tramp_frame->insn_size <= sizeof (tramp_frame->insn[0].bytes));
 
   data = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_data);
-  unwinder = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct frame_unwind);
-
   data->tramp_frame = tramp_frame;
-  unwinder->type = tramp_frame->frame_type;
+
-  unwinder->unwind_data = data;
+  unwinder = obstack_new <frame_unwind_trampoline> (gdbarch_obstack (gdbarch),
-  unwinder->sniffer = tramp_frame_sniffer;
+						    tramp_frame->frame_type,
-  unwinder->stop_reason = default_frame_unwind_stop_reason;
+						    data,
-  unwinder->this_id = tramp_frame_this_id;
+						    tramp_frame->prev_arch);
-  unwinder->prev_register = tramp_frame_prev_register;
-  unwinder->prev_arch = tramp_frame->prev_arch;
   frame_unwind_prepend_unwinder (gdbarch, unwinder);
 }

gdb/v850-tdep.c

@@ -1320,15 +1320,16 @@ v850_frame_this_id (frame_info_ptr this_frame, void **this_cache,
   *this_id = frame_id_build (cache->saved_regs[E_SP_REGNUM].addr (), cache->pc);
 }
 
-static const struct frame_unwind v850_frame_unwind = {
+static const struct frame_unwind_legacy v850_frame_unwind (
   "v850 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   v850_frame_this_id,
   v850_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 static CORE_ADDR
 v850_frame_base_address (frame_info_ptr this_frame, void **this_cache)

gdb/vax-tdep.c

@@ -386,16 +386,16 @@ vax_frame_prev_register (frame_info_ptr this_frame,
   return trad_frame_get_prev_register (this_frame, cache->saved_regs, regnum);
 }
 
-static const struct frame_unwind vax_frame_unwind =
+static const struct frame_unwind_legacy vax_frame_unwind (
-{
   "vax prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   vax_frame_this_id,
   vax_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 
 static CORE_ADDR

gdb/xstormy16-tdep.c

@@ -728,15 +728,16 @@ xstormy16_frame_base_address (frame_info_ptr this_frame, void **this_cache)
   return cache->base;
 }
 
-static const struct frame_unwind xstormy16_frame_unwind = {
+static const struct frame_unwind_legacy xstormy16_frame_unwind (
   "xstormy16 prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   xstormy16_frame_this_id,
   xstormy16_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 static const struct frame_base xstormy16_frame_base = {
   &xstormy16_frame_unwind,

gdb/xtensa-tdep.c

@@ -1496,17 +1496,17 @@ xtensa_frame_prev_register (frame_info_ptr this_frame,
 }
 
 
-static const struct frame_unwind
+static const struct frame_unwind_legacy
-xtensa_unwind =
+xtensa_unwind (
-{
   "xtensa prologue",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   xtensa_frame_this_id,
   xtensa_frame_prev_register,
   NULL,
   default_frame_sniffer
-};
+);
 
 static CORE_ADDR
 xtensa_frame_base_address (frame_info_ptr this_frame, void **this_cache)

gdb/z80-tdep.c

@@ -1063,11 +1063,10 @@ z80_insn_is_jump (struct gdbarch *gdbarch, CORE_ADDR addr)
   return 0;
 }
 
-static const struct frame_unwind
+static const struct frame_unwind_legacy z80_frame_unwind (
-z80_frame_unwind =
-{
   "z80",
   NORMAL_FRAME,
+  FRAME_UNWIND_ARCH,
   default_frame_unwind_stop_reason,
   z80_frame_this_id,
   z80_frame_prev_register,
@@ -1075,7 +1074,7 @@ z80_frame_unwind =
   default_frame_sniffer
   /*dealloc_cache*/
   /*prev_arch*/
-};
+);
 
 /* Initialize the gdbarch struct for the Z80 arch */
 static struct gdbarch *