gdb/

	* frame.c (frame_unwind_register): Throw an error if unwinding the
	register failed.
	* get_prev_frame_1 (get_prev_frame_1): Ask the unwinder if there's
	an unwind stop reason.
	(frame_stop_reason_string): Handle UNWIND_UNAVAILABLE.
	* frame.h (enum unwind_stop_reason) <UNWIND_OUTERMOST,
	UNWIND_UNAVAILABLE>: New.
	* inline-frame.c (inline_frame_unwind): Install
	default_frame_unwind_stop_reason.
	* frame-unwind.c: Include "exceptions.h".
	(frame_unwind_find_by_frame): Swallow NOT_AVAILABLE_ERROR errors.
	(default_frame_unwind_stop_reason): New.
	* frame-unwind.h (frame_unwind_stop_reason_ftype): New typedef.
	(default_frame_unwind_stop_reason): Declare.
	(struct frame_unwind) <stop_reason>: New function pointer.

	* dummy-frame.c: Install default_frame_unwind_stop_reason.
	* dwarf2-frame.c: Include exceptions.h.
	(struct dwarf2_frame_cache) <unavailable_retaddr>: New field.
	(dwarf2_frame_cache): Swallow NOT_AVAILABLE_ERROR errors when
	computing the CFA.  If such an error was thrown, set
	unavailable_retaddr.
	(dwarf2_frame_unwind_stop_reason): New.
	(dwarf2_frame_this_id): Don't build a frame id if the CFA was
	unavailable.
	(dwarf2_frame_unwind): Install dwarf2_frame_unwind_stop_reason.
	(dwarf2_signal_frame_unwind): Ditto.

	* amd64-tdep.c: Include "exceptions.h".
	(struct amd64_frame_cache): New field "base_p".
	(amd64_init_frame_cache): Clear it.
	(amd64_frame_cache_1): New, factored out from amd64_frame_cache.
	Avoid reading registers with functions that throw if the register
	is not necessary to compute the frame base.
	(amd64_frame_cache): Reimplement wrapping amd64_frame_cache_1, and
	swallowing NOT_AVAILABLE_ERROR.
	(amd64_frame_unwind_stop_reason): New.
	(amd64_frame_this_id): Don't build a frame id if the frame base
	was unavailable.
	(amd64_frame_unwind): Install amd64_frame_unwind_stop_reason.
	(amd64_sigtramp_frame_cache): Swallow NOT_AVAILABLE_ERROR, and set
	base_p if the frame base was computable.
	(amd64_sigtramp_frame_unwind_stop_reason): New.
	(amd64_sigtramp_frame_this_id): Don't build a frame id if the
	frame base was unavailable.
	(amd64_sigtramp_frame_unwind): Install
	amd64_sigtramp_frame_unwind_stop_reason.
	(amd64_epilogue_frame_cache): Swallow NOT_AVAILABLE_ERROR, and set
	base_p if the frame base was computable.
	(amd64_epilogue_frame_unwind_stop_reason): New.
	(amd64_epilogue_frame_this_id): Don't build a frame id if the
	frame base was unavailable.
	(amd64_epilogue_frame_unwind): Install
	amd64_epilogue_frame_unwind_stop_reason.
	* i386-tdep.c: Include "exceptions.h".
	(struct i386_frame_cache): New field "base_p".
	(i386_init_frame_cache): Clear it.
	(i386_frame_cache_1): New, factored out from amd64_frame_cache.
	Avoid reading registers with functions that throw if the register
	is not necessary to compute the frame base.
	(i386_frame_cache): Reimplement wrapping amd64_frame_cache_1, and
	swallowing NOT_AVAILABLE_ERROR.
	(i386_frame_unwind_stop_reason): New.
	(i386_frame_this_id): Don't build a frame id if the frame base was
	unavailable.
	(i386_frame_prev_register): Handle unavailable SP.
	(i386_frame_unwind): Install i386_frame_unwind_stop_reason.
	(i386_epilogue_frame_cache): Swallow NOT_AVAILABLE_ERROR, and set
	base_p if the frame base was computable.
	(i386_epilogue_frame_unwind_stop_reason): New.
	(i386_epilogue_frame_this_id): Don't build a frame id if the frame
	base was unavailable.
	(i386_epilogue_frame_unwind): Install
	i386_epilogue_frame_unwind_stop_reason.
	(i386_sigtramp_frame_cache): Swallow NOT_AVAILABLE_ERROR, and set
	base_p if the frame base was computable.
	(i386_sigtramp_frame_unwind_stop_reason): New.
	(i386_sigtramp_frame_this_id): Don't build a frame id if the frame
	base was unavailable.
	(i386_sigtramp_frame_unwind): Install
	i386_sigtramp_frame_unwind_stop_reason.
	* sentinel-frame.c (sentinel_frame_prev_register): Use the value
	type's size, not the register's.
	(sentinel_frame_unwind): Install default_frame_unwind_stop_reason.

	* alpha-mdebug-tdep.c (alpha_mdebug_frame_unwind): Install
	default_frame_unwind_stop_reason.
	* alpha-tdep.c (alpha_sigtramp_frame_unwind)
	(alpha_heuristic_frame_unwind): Ditto.
	* amd64obsd-tdep.c (amd64obsd_trapframe_unwind): Ditto.
	* arm-tdep.c (arm_prologue_unwind, arm_stub_unwind): Ditto.
	* avr-tdep.c (avr_frame_unwind): Ditto.
	* cris-tdep.c (cris_sigtramp_frame_unwind, cris_frame_unwind):
	Ditto.
	* frv-linux-tdep.c (frv_linux_sigtramp_frame_unwind): Ditto.
	* frv-tdep.c (frv_frame_unwind): Ditto.
	* h8300-tdep.c (h8300_frame_unwind): Ditto.
	* hppa-hpux-tdep.c (hppa_hpux_sigtramp_frame_unwind): Ditto.
	* hppa-linux-tdep.c (hppa_linux_sigtramp_frame_unwind): Ditto.
	* hppa-tdep.c (hppa_frame_unwind, hppa_fallback_frame_unwind)
	(hppa_stub_frame_unwind): Ditto.
	* i386obsd-tdep.c (i386obsd_trapframe_unwind): Ditto.
	* ia64-tdep.c (ia64_frame_unwind, ia64_sigtramp_frame_unwind)
	(ia64_libunwind_frame_unwind)
	(ia64_libunwind_sigtramp_frame_unwind): Ditto.
	* iq2000-tdep.c (iq2000_frame_unwind): Ditto.
	* lm32-tdep.c (lm32_frame_unwind): Ditto.
	* m32c-tdep.c (m32c_unwind): Ditto.
	* m32r-linux-tdep.c (m32r_linux_sigtramp_frame_unwind): Ditto.
	* m32r-tdep.c (m32r_frame_unwind): Ditto.
	* m68hc11-tdep.c (m68hc11_frame_unwind): Ditto.
	* m68k-tdep.c (m68k_frame_unwind): Ditto.
	* m68klinux-tdep.c (m68k_linux_sigtramp_frame_unwind): Ditto.
	* m88k-tdep.c (m88k_frame_unwind): Ditto.
	* mep-tdep.c (mep_frame_unwind): Ditto.
	* microblaze-tdep.c (microblaze_frame_unwind): Ditto.
	* mips-tdep.c (mips_insn16_frame_unwind, mips_insn32_frame_unwind)
	(mips_stub_frame_unwind): Ditto.
	* mn10300-tdep.c (mn10300_frame_unwind): Ditto.
	* moxie-tdep.c (moxie_frame_unwind): Ditto.
	* mt-tdep.c (mt_frame_unwind): Ditto.
	* ppc-linux-tdep.c (ppu2spu_unwind): Ditto.
	* ppcobsd-tdep.c (ppcobsd_sigtramp_frame_unwind): Ditto.
	* rs6000-tdep.c (rs6000_frame_unwind): Ditto.
	* s390-tdep.c (s390_frame_unwind, s390_stub_frame_unwind)
	(s390_sigtramp_frame_unwind): Ditto.
	* score-tdep.c (score_prologue_unwind): Ditto.
	* sh-tdep.c (sh_frame_unwind): Ditto.
	* sh64-tdep.c (sh64_frame_unwind): Ditto.
	* sparc-sol2-tdep.c (sparc32_sol2_sigtramp_frame_unwind): Ditto.
	* sparc-tdep.c (sparc32_frame_unwind): Ditto.
	* sparc64-sol2-tdep.c (sparc64_sol2_sigtramp_frame_unwind): Ditto.
	* sparc64-tdep.c (sparc64_frame_unwind): Ditto.
	* sparc64fbsd-tdep.c (sparc64fbsd_sigtramp_frame_unwind): Ditto.
	* sparc64nbsd-tdep.c (sparc64nbsd_sigcontext_frame_unwind): Ditto.
	* sparc64obsd-tdep.c (sparc64obsd_frame_unwind)
	(sparc64obsd_trapframe_unwind): Ditto.
	* sparcnbsd-tdep.c (sparc32nbsd_sigcontext_frame_unwind): Ditto.
	* sparcobsd-tdep.c (sparc32obsd_sigtramp_frame_unwind): Ditto.
	* spu-tdep.c (spu_frame_unwind, spu2ppu_unwind): Ditto.
	* v850-tdep.c (v850_frame_unwind): Ditto.
	* vax-tdep.c (vax_frame_unwind): Ditto.
	* vaxobsd-tdep.c (vaxobsd_sigtramp_frame_unwind): Ditto.
	* xstormy16-tdep.c (frame_unwind xstormy16_frame_unwind): Ditto.
	* xtensa-tdep.c (xtensa_unwind): Ditto.

63 files changed, 617 insertions, 109 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 0dbc501d99e..64d8391ca6c 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,151 @@
+2012-03-18  Pedro Alves  <pedro@codesourcery.com>
+
+	* frame.c (frame_unwind_register): Throw an error if unwinding the
+	register failed.
+	* get_prev_frame_1 (get_prev_frame_1): Ask the unwinder if there's
+	an unwind stop reason.
+	(frame_stop_reason_string): Handle UNWIND_UNAVAILABLE.
+	* frame.h (enum unwind_stop_reason) <UNWIND_OUTERMOST,
+	UNWIND_UNAVAILABLE>: New.
+	* inline-frame.c (inline_frame_unwind): Install
+	default_frame_unwind_stop_reason.
+	* frame-unwind.c: Include "exceptions.h".
+	(frame_unwind_find_by_frame): Swallow NOT_AVAILABLE_ERROR errors.
+	(default_frame_unwind_stop_reason): New.
+	* frame-unwind.h (frame_unwind_stop_reason_ftype): New typedef.
+	(default_frame_unwind_stop_reason): Declare.
+	(struct frame_unwind) <stop_reason>: New function pointer.
+
+	* dummy-frame.c: Install default_frame_unwind_stop_reason.
+	* dwarf2-frame.c: Include exceptions.h.
+	(struct dwarf2_frame_cache) <unavailable_retaddr>: New field.
+	(dwarf2_frame_cache): Swallow NOT_AVAILABLE_ERROR errors when
+	computing the CFA.  If such an error was thrown, set
+	unavailable_retaddr.
+	(dwarf2_frame_unwind_stop_reason): New.
+	(dwarf2_frame_this_id): Don't build a frame id if the CFA was
+	unavailable.
+	(dwarf2_frame_unwind): Install dwarf2_frame_unwind_stop_reason.
+	(dwarf2_signal_frame_unwind): Ditto.
+
+	* amd64-tdep.c: Include "exceptions.h".
+	(struct amd64_frame_cache): New field "base_p".
+	(amd64_init_frame_cache): Clear it.
+	(amd64_frame_cache_1): New, factored out from amd64_frame_cache.
+	Avoid reading registers with functions that throw if the register
+	is not necessary to compute the frame base.
+	(amd64_frame_cache): Reimplement wrapping amd64_frame_cache_1, and
+	swallowing NOT_AVAILABLE_ERROR.
+	(amd64_frame_unwind_stop_reason): New.
+	(amd64_frame_this_id): Don't build a frame id if the frame base
+	was unavailable.
+	(amd64_frame_unwind): Install amd64_frame_unwind_stop_reason.
+	(amd64_sigtramp_frame_cache): Swallow NOT_AVAILABLE_ERROR, and set
+	base_p if the frame base was computable.
+	(amd64_sigtramp_frame_unwind_stop_reason): New.
+	(amd64_sigtramp_frame_this_id): Don't build a frame id if the
+	frame base was unavailable.
+	(amd64_sigtramp_frame_unwind): Install
+	amd64_sigtramp_frame_unwind_stop_reason.
+	(amd64_epilogue_frame_cache): Swallow NOT_AVAILABLE_ERROR, and set
+	base_p if the frame base was computable.
+	(amd64_epilogue_frame_unwind_stop_reason): New.
+	(amd64_epilogue_frame_this_id): Don't build a frame id if the
+	frame base was unavailable.
+	(amd64_epilogue_frame_unwind): Install
+	amd64_epilogue_frame_unwind_stop_reason.
+	* i386-tdep.c: Include "exceptions.h".
+	(struct i386_frame_cache): New field "base_p".
+	(i386_init_frame_cache): Clear it.
+	(i386_frame_cache_1): New, factored out from amd64_frame_cache.
+	Avoid reading registers with functions that throw if the register
+	is not necessary to compute the frame base.
+	(i386_frame_cache): Reimplement wrapping amd64_frame_cache_1, and
+	swallowing NOT_AVAILABLE_ERROR.
+	(i386_frame_unwind_stop_reason): New.
+	(i386_frame_this_id): Don't build a frame id if the frame base was
+	unavailable.
+	(i386_frame_prev_register): Handle unavailable SP.
+	(i386_frame_unwind): Install i386_frame_unwind_stop_reason.
+	(i386_epilogue_frame_cache): Swallow NOT_AVAILABLE_ERROR, and set
+	base_p if the frame base was computable.
+	(i386_epilogue_frame_unwind_stop_reason): New.
+	(i386_epilogue_frame_this_id): Don't build a frame id if the frame
+	base was unavailable.
+	(i386_epilogue_frame_unwind): Install
+	i386_epilogue_frame_unwind_stop_reason.
+	(i386_sigtramp_frame_cache): Swallow NOT_AVAILABLE_ERROR, and set
+	base_p if the frame base was computable.
+	(i386_sigtramp_frame_unwind_stop_reason): New.
+	(i386_sigtramp_frame_this_id): Don't build a frame id if the frame
+	base was unavailable.
+	(i386_sigtramp_frame_unwind): Install
+	i386_sigtramp_frame_unwind_stop_reason.
+	* sentinel-frame.c (sentinel_frame_prev_register): Use the value
+	type's size, not the register's.
+	(sentinel_frame_unwind): Install default_frame_unwind_stop_reason.
+
+	* alpha-mdebug-tdep.c (alpha_mdebug_frame_unwind): Install
+	default_frame_unwind_stop_reason.
+	* alpha-tdep.c (alpha_sigtramp_frame_unwind)
+	(alpha_heuristic_frame_unwind): Ditto.
+	* amd64obsd-tdep.c (amd64obsd_trapframe_unwind): Ditto.
+	* arm-tdep.c (arm_prologue_unwind, arm_stub_unwind): Ditto.
+	* avr-tdep.c (avr_frame_unwind): Ditto.
+	* cris-tdep.c (cris_sigtramp_frame_unwind, cris_frame_unwind):
+	Ditto.
+	* frv-linux-tdep.c (frv_linux_sigtramp_frame_unwind): Ditto.
+	* frv-tdep.c (frv_frame_unwind): Ditto.
+	* h8300-tdep.c (h8300_frame_unwind): Ditto.
+	* hppa-hpux-tdep.c (hppa_hpux_sigtramp_frame_unwind): Ditto.
+	* hppa-linux-tdep.c (hppa_linux_sigtramp_frame_unwind): Ditto.
+	* hppa-tdep.c (hppa_frame_unwind, hppa_fallback_frame_unwind)
+	(hppa_stub_frame_unwind): Ditto.
+	* i386obsd-tdep.c (i386obsd_trapframe_unwind): Ditto.
+	* ia64-tdep.c (ia64_frame_unwind, ia64_sigtramp_frame_unwind)
+	(ia64_libunwind_frame_unwind)
+	(ia64_libunwind_sigtramp_frame_unwind): Ditto.
+	* iq2000-tdep.c (iq2000_frame_unwind): Ditto.
+	* lm32-tdep.c (lm32_frame_unwind): Ditto.
+	* m32c-tdep.c (m32c_unwind): Ditto.
+	* m32r-linux-tdep.c (m32r_linux_sigtramp_frame_unwind): Ditto.
+	* m32r-tdep.c (m32r_frame_unwind): Ditto.
+	* m68hc11-tdep.c (m68hc11_frame_unwind): Ditto.
+	* m68k-tdep.c (m68k_frame_unwind): Ditto.
+	* m68klinux-tdep.c (m68k_linux_sigtramp_frame_unwind): Ditto.
+	* m88k-tdep.c (m88k_frame_unwind): Ditto.
+	* mep-tdep.c (mep_frame_unwind): Ditto.
+	* microblaze-tdep.c (microblaze_frame_unwind): Ditto.
+	* mips-tdep.c (mips_insn16_frame_unwind, mips_insn32_frame_unwind)
+	(mips_stub_frame_unwind): Ditto.
+	* mn10300-tdep.c (mn10300_frame_unwind): Ditto.
+	* moxie-tdep.c (moxie_frame_unwind): Ditto.
+	* mt-tdep.c (mt_frame_unwind): Ditto.
+	* ppc-linux-tdep.c (ppu2spu_unwind): Ditto.
+	* ppcobsd-tdep.c (ppcobsd_sigtramp_frame_unwind): Ditto.
+	* rs6000-tdep.c (rs6000_frame_unwind): Ditto.
+	* s390-tdep.c (s390_frame_unwind, s390_stub_frame_unwind)
+	(s390_sigtramp_frame_unwind): Ditto.
+	* score-tdep.c (score_prologue_unwind): Ditto.
+	* sh-tdep.c (sh_frame_unwind): Ditto.
+	* sh64-tdep.c (sh64_frame_unwind): Ditto.
+	* sparc-sol2-tdep.c (sparc32_sol2_sigtramp_frame_unwind): Ditto.
+	* sparc-tdep.c (sparc32_frame_unwind): Ditto.
+	* sparc64-sol2-tdep.c (sparc64_sol2_sigtramp_frame_unwind): Ditto.
+	* sparc64-tdep.c (sparc64_frame_unwind): Ditto.
+	* sparc64fbsd-tdep.c (sparc64fbsd_sigtramp_frame_unwind): Ditto.
+	* sparc64nbsd-tdep.c (sparc64nbsd_sigcontext_frame_unwind): Ditto.
+	* sparc64obsd-tdep.c (sparc64obsd_frame_unwind)
+	(sparc64obsd_trapframe_unwind): Ditto.
+	* sparcnbsd-tdep.c (sparc32nbsd_sigcontext_frame_unwind): Ditto.
+	* sparcobsd-tdep.c (sparc32obsd_sigtramp_frame_unwind): Ditto.
+	* spu-tdep.c (spu_frame_unwind, spu2ppu_unwind): Ditto.
+	* v850-tdep.c (v850_frame_unwind): Ditto.
+	* vax-tdep.c (vax_frame_unwind): Ditto.
+	* vaxobsd-tdep.c (vaxobsd_sigtramp_frame_unwind): Ditto.
+	* xstormy16-tdep.c (frame_unwind xstormy16_frame_unwind): Ditto.
+	* xtensa-tdep.c (xtensa_unwind): Ditto.
+
 2011-03-18  Pedro Alves  <pedro@codesourcery.com>
 
 	* tui/tui-hooks.c (tui_selected_frame_level_changed_hook): Assume
diff --git a/gdb/alpha-mdebug-tdep.c b/gdb/alpha-mdebug-tdep.c
index 8773437e21e..f48a121e2df 100644
--- a/gdb/alpha-mdebug-tdep.c
+++ b/gdb/alpha-mdebug-tdep.c
@@ -336,6 +336,7 @@ alpha_mdebug_frame_sniffer (const struct frame_unwind *self,
 
 static const struct frame_unwind alpha_mdebug_frame_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   alpha_mdebug_frame_this_id,
   alpha_mdebug_frame_prev_register,
   NULL,
diff --git a/gdb/alpha-tdep.c b/gdb/alpha-tdep.c
index 2f309a7c998..51eb6e431d1 100644
--- a/gdb/alpha-tdep.c
+++ b/gdb/alpha-tdep.c
@@ -936,6 +936,7 @@ alpha_sigtramp_frame_sniffer (const struct frame_unwind *self,
 
 static const struct frame_unwind alpha_sigtramp_frame_unwind = {
   SIGTRAMP_FRAME,
+  default_frame_unwind_stop_reason,
   alpha_sigtramp_frame_this_id,
   alpha_sigtramp_frame_prev_register,
   NULL,
@@ -1351,6 +1352,7 @@ alpha_heuristic_frame_prev_register (struct frame_info *this_frame,
 
 static const struct frame_unwind alpha_heuristic_frame_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   alpha_heuristic_frame_this_id,
   alpha_heuristic_frame_prev_register,
   NULL,
diff --git a/gdb/amd64-tdep.c b/gdb/amd64-tdep.c
index 54b17236db9..9b5d5bb43af 100644
--- a/gdb/amd64-tdep.c
+++ b/gdb/amd64-tdep.c
@@ -38,7 +38,7 @@
 #include "symfile.h"
 #include "disasm.h"
 #include "gdb_assert.h"
-
+#include "exceptions.h"
 #include "amd64-tdep.h"
 #include "i387-tdep.h"
 
@@ -1635,6 +1635,7 @@ struct amd64_frame_cache
 {
   /* Base address.  */
   CORE_ADDR base;
+  int base_p;
   CORE_ADDR sp_offset;
   CORE_ADDR pc;
 
@@ -1656,6 +1657,7 @@ amd64_init_frame_cache (struct amd64_frame_cache *cache)
 
   /* Base address.  */
   cache->base = 0;
+  cache->base_p = 0;
   cache->sp_offset = -8;
   cache->pc = 0;
 
@@ -1913,33 +1915,20 @@ amd64_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR start_pc)
 
 /* Normal frames.  */
 
-static struct amd64_frame_cache *
-amd64_frame_cache (struct frame_info *this_frame, void **this_cache)
+static void
+amd64_frame_cache_1 (struct frame_info *this_frame,
+		     struct amd64_frame_cache *cache)
 {
   struct gdbarch *gdbarch = get_frame_arch (this_frame);
   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
-  struct amd64_frame_cache *cache;
   gdb_byte buf[8];
   int i;
 
-  if (*this_cache)
-    return *this_cache;
-
-  cache = amd64_alloc_frame_cache ();
-  *this_cache = cache;
-
   cache->pc = get_frame_func (this_frame);
   if (cache->pc != 0)
     amd64_analyze_prologue (gdbarch, cache->pc, get_frame_pc (this_frame),
 			    cache);
 
-  if (cache->saved_sp_reg != -1)
-    {
-      /* Stack pointer has been saved.  */
-      get_frame_register (this_frame, cache->saved_sp_reg, buf);
-      cache->saved_sp = extract_unsigned_integer(buf, 8, byte_order);
-    }
-
   if (cache->frameless_p)
     {
       /* We didn't find a valid frame.  If we're at the start of a
@@ -1951,6 +1940,10 @@ amd64_frame_cache (struct frame_info *this_frame, void **this_cache)
 
       if (cache->saved_sp_reg != -1)
 	{
+	  /* Stack pointer has been saved.  */
+	  get_frame_register (this_frame, cache->saved_sp_reg, buf);
+	  cache->saved_sp = extract_unsigned_integer (buf, 8, byte_order);
+
 	  /* We're halfway aligning the stack.  */
 	  cache->base = ((cache->saved_sp - 8) & 0xfffffffffffffff0LL) - 8;
 	  cache->saved_regs[AMD64_RIP_REGNUM] = cache->saved_sp - 8;
@@ -1988,9 +1981,48 @@ amd64_frame_cache (struct frame_info *this_frame, void **this_cache)
     if (cache->saved_regs[i] != -1)
       cache->saved_regs[i] += cache->base;
 
+  cache->base_p = 1;
+}
+
+static struct amd64_frame_cache *
+amd64_frame_cache (struct frame_info *this_frame, void **this_cache)
+{
+  volatile struct gdb_exception ex;
+  struct amd64_frame_cache *cache;
+
+  if (*this_cache)
+    return *this_cache;
+
+  cache = amd64_alloc_frame_cache ();
+  *this_cache = cache;
+
+  TRY_CATCH (ex, RETURN_MASK_ERROR)
+    {
+      amd64_frame_cache_1 (this_frame, cache);
+    }
+  if (ex.reason < 0 && ex.error != NOT_AVAILABLE_ERROR)
+    throw_exception (ex);
+
   return cache;
 }
 
+static enum unwind_stop_reason
+amd64_frame_unwind_stop_reason (struct frame_info *this_frame,
+				void **this_cache)
+{
+  struct amd64_frame_cache *cache =
+    amd64_frame_cache (this_frame, this_cache);
+
+  if (!cache->base_p)
+    return UNWIND_UNAVAILABLE;
+
+  /* This marks the outermost frame.  */
+  if (cache->base == 0)
+    return UNWIND_OUTERMOST;
+
+  return UNWIND_NO_REASON;
+}
+
 static void
 amd64_frame_this_id (struct frame_info *this_frame, void **this_cache,
 		     struct frame_id *this_id)
@@ -1998,6 +2030,9 @@ amd64_frame_this_id (struct frame_info *this_frame, void **this_cache,
   struct amd64_frame_cache *cache =
     amd64_frame_cache (this_frame, this_cache);
 
+  if (!cache->base_p)
+    return;
+
   /* This marks the outermost frame.  */
   if (cache->base == 0)
     return;
@@ -2028,6 +2063,7 @@ amd64_frame_prev_register (struct frame_info *this_frame, void **this_cache,
 static const struct frame_unwind amd64_frame_unwind =
 {
   NORMAL_FRAME,
+  amd64_frame_unwind_stop_reason,
   amd64_frame_this_id,
   amd64_frame_prev_register,
   NULL,
@@ -2047,6 +2083,7 @@ amd64_sigtramp_frame_cache (struct frame_info *this_frame, void **this_cache)
   struct gdbarch *gdbarch = get_frame_arch (this_frame);
   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
+  volatile struct gdb_exception ex;
   struct amd64_frame_cache *cache;
   CORE_ADDR addr;
   gdb_byte buf[8];
@@ -2057,20 +2094,40 @@ amd64_sigtramp_frame_cache (struct frame_info *this_frame, void **this_cache)
 
   cache = amd64_alloc_frame_cache ();
 
-  get_frame_register (this_frame, AMD64_RSP_REGNUM, buf);
-  cache->base = extract_unsigned_integer (buf, 8, byte_order) - 8;
+  TRY_CATCH (ex, RETURN_MASK_ERROR)
+    {
+      get_frame_register (this_frame, AMD64_RSP_REGNUM, buf);
+      cache->base = extract_unsigned_integer (buf, 8, byte_order) - 8;
+
+      addr = tdep->sigcontext_addr (this_frame);
+      gdb_assert (tdep->sc_reg_offset);
+      gdb_assert (tdep->sc_num_regs <= AMD64_NUM_SAVED_REGS);
+      for (i = 0; i < tdep->sc_num_regs; i++)
+	if (tdep->sc_reg_offset[i] != -1)
+	  cache->saved_regs[i] = addr + tdep->sc_reg_offset[i];
 
-  addr = tdep->sigcontext_addr (this_frame);
-  gdb_assert (tdep->sc_reg_offset);
-  gdb_assert (tdep->sc_num_regs <= AMD64_NUM_SAVED_REGS);
-  for (i = 0; i < tdep->sc_num_regs; i++)
-    if (tdep->sc_reg_offset[i] != -1)
-      cache->saved_regs[i] = addr + tdep->sc_reg_offset[i];
+      cache->base_p = 1;
+    }
+  if (ex.reason < 0 && ex.error != NOT_AVAILABLE_ERROR)
+    throw_exception (ex);
 
   *this_cache = cache;
   return cache;
 }
 
+static enum unwind_stop_reason
+amd64_sigtramp_frame_unwind_stop_reason (struct frame_info *this_frame,
+					 void **this_cache)
+{
+  struct amd64_frame_cache *cache =
+    amd64_sigtramp_frame_cache (this_frame, this_cache);
+
+  if (!cache->base_p)
+    return UNWIND_UNAVAILABLE;
+
+  return UNWIND_NO_REASON;
+}
+
 static void
 amd64_sigtramp_frame_this_id (struct frame_info *this_frame,
 			      void **this_cache, struct frame_id *this_id)
@@ -2078,6 +2135,9 @@ amd64_sigtramp_frame_this_id (struct frame_info *this_frame,
   struct amd64_frame_cache *cache =
     amd64_sigtramp_frame_cache (this_frame, this_cache);
 
+  if (!cache->base_p)
+    return;
+
   (*this_id) = frame_id_build (cache->base + 16, get_frame_pc (this_frame));
 }
 
@@ -2124,6 +2184,7 @@ amd64_sigtramp_frame_sniffer (const struct frame_unwind *self,
 static const struct frame_unwind amd64_sigtramp_frame_unwind =
 {
   SIGTRAMP_FRAME,
+  amd64_sigtramp_frame_unwind_stop_reason,
   amd64_sigtramp_frame_this_id,
   amd64_sigtramp_frame_prev_register,
   NULL,
@@ -2185,6 +2246,7 @@ amd64_epilogue_frame_cache (struct frame_info *this_frame, void **this_cache)
 {
   struct gdbarch *gdbarch = get_frame_arch (this_frame);
   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
+  volatile struct gdb_exception ex;
   struct amd64_frame_cache *cache;
   gdb_byte buf[8];
 
@@ -2194,23 +2256,43 @@ amd64_epilogue_frame_cache (struct frame_info *this_frame, void **this_cache)
   cache = amd64_alloc_frame_cache ();
   *this_cache = cache;
 
-  /* Cache base will be %esp plus cache->sp_offset (-8).  */
-  get_frame_register (this_frame, AMD64_RSP_REGNUM, buf);
-  cache->base = extract_unsigned_integer (buf, 8, 
-					  byte_order) + cache->sp_offset;
+  TRY_CATCH (ex, RETURN_MASK_ERROR)
+    {
+      /* Cache base will be %esp plus cache->sp_offset (-8).  */
+      get_frame_register (this_frame, AMD64_RSP_REGNUM, buf);
+      cache->base = extract_unsigned_integer (buf, 8,
+					      byte_order) + cache->sp_offset;
+
+      /* Cache pc will be the frame func.  */
+      cache->pc = get_frame_pc (this_frame);
 
-  /* Cache pc will be the frame func.  */
-  cache->pc = get_frame_pc (this_frame);
+      /* The saved %esp will be at cache->base plus 16.  */
+      cache->saved_sp = cache->base + 16;
 
-  /* The saved %esp will be at cache->base plus 16.  */
-  cache->saved_sp = cache->base + 16;
+      /* The saved %eip will be at cache->base plus 8.  */
+      cache->saved_regs[AMD64_RIP_REGNUM] = cache->base + 8;
 
-  /* The saved %eip will be at cache->base plus 8.  */
-  cache->saved_regs[AMD64_RIP_REGNUM] = cache->base + 8;
+      cache->base_p = 1;
+    }
+  if (ex.reason < 0 && ex.error != NOT_AVAILABLE_ERROR)
+    throw_exception (ex);
 
   return cache;
 }
 
+static enum unwind_stop_reason
+amd64_epilogue_frame_unwind_stop_reason (struct frame_info *this_frame,
+					 void **this_cache)
+{
+  struct amd64_frame_cache *cache
+    = amd64_epilogue_frame_cache (this_frame, this_cache);
+
+  if (!cache->base_p)
+    return UNWIND_UNAVAILABLE;
+
+  return UNWIND_NO_REASON;
+}
+
 static void
 amd64_epilogue_frame_this_id (struct frame_info *this_frame,
 			      void **this_cache,
@@ -2219,12 +2301,16 @@ amd64_epilogue_frame_this_id (struct frame_info *this_frame,
   struct amd64_frame_cache *cache = amd64_epilogue_frame_cache (this_frame,
 							       this_cache);
 
+  if (!cache->base_p)
+    return;
+
   (*this_id) = frame_id_build (cache->base + 8, cache->pc);
 }
 
 static const struct frame_unwind amd64_epilogue_frame_unwind =
 {
   NORMAL_FRAME,
+  amd64_epilogue_frame_unwind_stop_reason,
   amd64_epilogue_frame_this_id,
   amd64_frame_prev_register,
   NULL, 
diff --git a/gdb/amd64obsd-tdep.c b/gdb/amd64obsd-tdep.c
index f5dd259aa38..2ff5c8f9182 100644
--- a/gdb/amd64obsd-tdep.c
+++ b/gdb/amd64obsd-tdep.c
@@ -437,6 +437,7 @@ static const struct frame_unwind amd64obsd_trapframe_unwind = {
      frame, but SIGTRAMP_FRAME would print <signal handler called>,
      which really is not what we want here.  */
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   amd64obsd_trapframe_this_id,
   amd64obsd_trapframe_prev_register,
   NULL,
diff --git a/gdb/arm-tdep.c b/gdb/arm-tdep.c
index 0020b47c0d2..754c431fabd 100644
--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -2146,6 +2146,7 @@ arm_prologue_prev_register (struct frame_info *this_frame,
 
 struct frame_unwind arm_prologue_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   arm_prologue_this_id,
   arm_prologue_prev_register,
   NULL,
@@ -2884,6 +2885,7 @@ arm_exidx_unwind_sniffer (const struct frame_unwind *self,
 
 struct frame_unwind arm_exidx_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   arm_prologue_this_id,
   arm_prologue_prev_register,
   NULL,
@@ -2939,6 +2941,7 @@ arm_stub_unwind_sniffer (const struct frame_unwind *self,
 
 struct frame_unwind arm_stub_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   arm_stub_this_id,
   arm_prologue_prev_register,
   NULL,
diff --git a/gdb/avr-tdep.c b/gdb/avr-tdep.c
index 31dd7df4ab5..20e7fcad33e 100644
--- a/gdb/avr-tdep.c
+++ b/gdb/avr-tdep.c
@@ -1131,6 +1131,7 @@ avr_frame_prev_register (struct frame_info *this_frame,
 
 static const struct frame_unwind avr_frame_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   avr_frame_this_id,
   avr_frame_prev_register,
   NULL,
diff --git a/gdb/bfin-tdep.c b/gdb/bfin-tdep.c
index 8c0cb5a325b..8322af5f81b 100644
--- a/gdb/bfin-tdep.c
+++ b/gdb/bfin-tdep.c
@@ -376,6 +376,7 @@ bfin_frame_prev_register (struct frame_info *this_frame,
 static const struct frame_unwind bfin_frame_unwind =
 {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   bfin_frame_this_id,
   bfin_frame_prev_register,
   NULL,
diff --git a/gdb/cris-tdep.c b/gdb/cris-tdep.c
index f99eabd4652..f79e84cd2e1 100644
--- a/gdb/cris-tdep.c
+++ b/gdb/cris-tdep.c
@@ -448,6 +448,7 @@ cris_sigtramp_frame_sniffer (const struct frame_unwind *self,
 static const struct frame_unwind cris_sigtramp_frame_unwind =
 {
   SIGTRAMP_FRAME,
+  default_frame_unwind_stop_reason,
   cris_sigtramp_frame_this_id,
   cris_sigtramp_frame_prev_register,
   NULL,
@@ -985,6 +986,7 @@ cris_push_dummy_call (struct gdbarch *gdbarch, struct value *function,
 static const struct frame_unwind cris_frame_unwind = 
 {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   cris_frame_this_id,
   cris_frame_prev_register,
   NULL,
diff --git a/gdb/dummy-frame.c b/gdb/dummy-frame.c
index f63659fd223..709cd684951 100644
--- a/gdb/dummy-frame.c
+++ b/gdb/dummy-frame.c
@@ -278,6 +278,7 @@ dummy_frame_this_id (struct frame_info *this_frame,
 const struct frame_unwind dummy_frame_unwind =
 {
   DUMMY_FRAME,
+  default_frame_unwind_stop_reason,
   dummy_frame_this_id,
   dummy_frame_prev_register,
   NULL,
diff --git a/gdb/dwarf2-frame.c b/gdb/dwarf2-frame.c
index edd6a9c5267..e78c3284ade 100644
--- a/gdb/dwarf2-frame.c
+++ b/gdb/dwarf2-frame.c
@@ -40,6 +40,7 @@
 #include "dwarf2-frame.h"
 #include "ax.h"
 #include "dwarf2loc.h"
+#include "exceptions.h"
 
 struct comp_unit;
 
@@ -986,6 +987,10 @@ struct dwarf2_frame_cache
   /* DWARF Call Frame Address.  */
   CORE_ADDR cfa;
 
+  /* Set if the return address column was marked as unavailable
+     (required non-collected memory or registers to compute).  */
+  int unavailable_retaddr;
+
   /* Set if the return address column was marked as undefined.  */
   int undefined_retaddr;
 
@@ -1013,6 +1018,7 @@ dwarf2_frame_cache (struct frame_info *this_frame, void **this_cache)
   struct dwarf2_frame_cache *cache;
   struct dwarf2_frame_state *fs;
   struct dwarf2_fde *fde;
+  volatile struct gdb_exception ex;
 
   if (*this_cache)
     return *this_cache;
@@ -1020,10 +1026,10 @@ dwarf2_frame_cache (struct frame_info *this_frame, void **this_cache)
   /* Allocate a new cache.  */
   cache = FRAME_OBSTACK_ZALLOC (struct dwarf2_frame_cache);
   cache->reg = FRAME_OBSTACK_CALLOC (num_regs, struct dwarf2_frame_state_reg);
+  *this_cache = cache;
 
   /* Allocate and initialize the frame state.  */
-  fs = XMALLOC (struct dwarf2_frame_state);
-  memset (fs, 0, sizeof (struct dwarf2_frame_state));
+  fs = XZALLOC (struct dwarf2_frame_state);
   old_chain = make_cleanup (dwarf2_frame_state_free, fs);
 
   /* Unwind the PC.
@@ -1068,26 +1074,39 @@ dwarf2_frame_cache (struct frame_info *this_frame, void **this_cache)
   execute_cfa_program (fde, fde->instructions, fde->end, gdbarch,
 		       get_frame_pc (this_frame), fs);
 
-  /* Calculate the CFA.  */
-  switch (fs->regs.cfa_how)
+  TRY_CATCH (ex, RETURN_MASK_ERROR)
     {
-    case CFA_REG_OFFSET:
-      cache->cfa = read_reg (this_frame, fs->regs.cfa_reg);
-      if (fs->armcc_cfa_offsets_reversed)
-	cache->cfa -= fs->regs.cfa_offset;
-      else
-	cache->cfa += fs->regs.cfa_offset;
-      break;
-
-    case CFA_EXP:
-      cache->cfa =
-	execute_stack_op (fs->regs.cfa_exp, fs->regs.cfa_exp_len,
-			  cache->addr_size, cache->text_offset,
-			  this_frame, 0, 0);
-      break;
+      /* Calculate the CFA.  */
+      switch (fs->regs.cfa_how)
+	{
+	case CFA_REG_OFFSET:
+	  cache->cfa = read_reg (this_frame, fs->regs.cfa_reg);
+	  if (fs->armcc_cfa_offsets_reversed)
+	    cache->cfa -= fs->regs.cfa_offset;
+	  else
+	    cache->cfa += fs->regs.cfa_offset;
+	  break;
+
+	case CFA_EXP:
+	  cache->cfa =
+	    execute_stack_op (fs->regs.cfa_exp, fs->regs.cfa_exp_len,
+			      cache->addr_size, cache->text_offset,
+			      this_frame, 0, 0);
+	  break;
+
+	default:
+	  internal_error (__FILE__, __LINE__, _("Unknown CFA rule."));
+	}
+    }
+  if (ex.reason < 0)
+    {
+      if (ex.error == NOT_AVAILABLE_ERROR)
+	{
+	  cache->unavailable_retaddr = 1;
+	  return cache;
+	}
 
-    default:
-      internal_error (__FILE__, __LINE__, _("Unknown CFA rule."));
+      throw_exception (ex);
     }
 
   /* Initialize the register state.  */
@@ -1193,10 +1212,25 @@ incomplete CFI data; unspecified registers (e.g., %s) at %s"),
 
   do_cleanups (old_chain);
 
-  *this_cache = cache;
   return cache;
 }
 
+static enum unwind_stop_reason
+dwarf2_frame_unwind_stop_reason (struct frame_info *this_frame,
+				 void **this_cache)
+{
+  struct dwarf2_frame_cache *cache
+    = dwarf2_frame_cache (this_frame, this_cache);
+
+  if (cache->unavailable_retaddr)
+    return UNWIND_UNAVAILABLE;
+
+  if (cache->undefined_retaddr)
+    return UNWIND_OUTERMOST;
+
+  return UNWIND_NO_REASON;
+}
+
 static void
 dwarf2_frame_this_id (struct frame_info *this_frame, void **this_cache,
 		      struct frame_id *this_id)
@@ -1204,6 +1238,9 @@ dwarf2_frame_this_id (struct frame_info *this_frame, void **this_cache,
   struct dwarf2_frame_cache *cache =
     dwarf2_frame_cache (this_frame, this_cache);
 
+  if (cache->unavailable_retaddr)
+    return;
+
   if (cache->undefined_retaddr)
     return;
 
@@ -1321,6 +1358,7 @@ dwarf2_frame_sniffer (const struct frame_unwind *self,
 static const struct frame_unwind dwarf2_frame_unwind =
 {
   NORMAL_FRAME,
+  dwarf2_frame_unwind_stop_reason,
   dwarf2_frame_this_id,
   dwarf2_frame_prev_register,
   NULL,
@@ -1330,6 +1368,7 @@ static const struct frame_unwind dwarf2_frame_unwind =
 static const struct frame_unwind dwarf2_signal_frame_unwind =
 {
   SIGTRAMP_FRAME,
+  dwarf2_frame_unwind_stop_reason,
   dwarf2_frame_this_id,
   dwarf2_frame_prev_register,
   NULL,
diff --git a/gdb/frame-unwind.c b/gdb/frame-unwind.c
index 27a53502346..cc04b301101 100644
--- a/gdb/frame-unwind.c
+++ b/gdb/frame-unwind.c
@@ -25,7 +25,7 @@
 #include "inline-frame.h"
 #include "value.h"
 #include "regcache.h"
-
+#include "exceptions.h"
 #include "gdb_assert.h"
 #include "gdb_obstack.h"
 
@@ -103,14 +103,31 @@ frame_unwind_find_by_frame (struct frame_info *this_frame, void **this_cache)
   for (entry = table->list; entry != NULL; entry = entry->next)
     {
       struct cleanup *old_cleanup;
+      volatile struct gdb_exception ex;
+      int res = 0;
 
       old_cleanup = frame_prepare_for_sniffer (this_frame, entry->unwinder);
-      if (entry->unwinder->sniffer (entry->unwinder, this_frame,
-				    this_cache))
+
+      TRY_CATCH (ex, RETURN_MASK_ERROR)
 	{
-	  discard_cleanups (old_cleanup);
-	  return;
+	  res = entry->unwinder->sniffer (entry->unwinder, this_frame,
+					  this_cache);
 	}
+      if (ex.reason < 0 && ex.error == NOT_AVAILABLE_ERROR)
+	{
+	  /* This usually means that not even the PC is available,
+	     thus most unwinders aren't able to determine if they're
+	     the best fit.  Keep trying.  Fallback prologue unwinders
+	     should always accept the frame.  */
+	}
+      else if (ex.reason < 0)
+	throw_exception (ex);
+      else if (res)
+        {
+          discard_cleanups (old_cleanup);
+          return;
+        }
+
       do_cleanups (old_cleanup);
     }
   internal_error (__FILE__, __LINE__, _("frame_unwind_find_by_frame failed"));
@@ -127,6 +144,16 @@ default_frame_sniffer (const struct frame_unwind *self,
   return 1;
 }
 
+/* A default frame unwinder stop_reason callback that always claims
+   the frame is unwindable.  */
+
+enum unwind_stop_reason
+default_frame_unwind_stop_reason (struct frame_info *this_frame,
+				  void **this_cache)
+{
+  return UNWIND_NO_REASON;
+}
+
 /* Helper functions for value-based register unwinding.  These return
    a (possibly lazy) value of the appropriate type.  */
 
diff --git a/gdb/frame-unwind.h b/gdb/frame-unwind.h
index e449766b253..5b04a1cb306 100644
--- a/gdb/frame-unwind.h
+++ b/gdb/frame-unwind.h
@@ -51,6 +51,9 @@ typedef int (frame_sniffer_ftype) (const struct frame_unwind *self,
 				   struct frame_info *this_frame,
 				   void **this_prologue_cache);
 
+typedef enum unwind_stop_reason (frame_unwind_stop_reason_ftype)
+  (struct frame_info *this_frame, void **this_prologue_cache);
+
 /* A default frame sniffer which always accepts the frame.  Used by
    fallback prologue unwinders.  */
 
@@ -58,6 +61,13 @@ int default_frame_sniffer (const struct frame_unwind *self,
 			   struct frame_info *this_frame,
 			   void **this_prologue_cache);
 
+/* A default stop_reason callback which always claims the frame is
+   unwindable.  */
+
+enum unwind_stop_reason
+  default_frame_unwind_stop_reason (struct frame_info *this_frame,
+				    void **this_cache);
+
 /* Assuming the frame chain: (outer) prev <-> this <-> next (inner);
    use THIS frame, and through it the NEXT frame's register unwind
    method, to determine the frame ID of THIS frame.
@@ -136,6 +146,7 @@ struct frame_unwind
   enum frame_type type;
   /* Should an attribute indicating the frame's address-in-block go
      here?  */
+  frame_unwind_stop_reason_ftype *stop_reason;
   frame_this_id_ftype *this_id;
   frame_prev_register_ftype *prev_register;
   const struct frame_data *unwind_data;
diff --git a/gdb/frame.c b/gdb/frame.c
index a817e4d6eb8..7a3519222ff 100644
--- a/gdb/frame.c
+++ b/gdb/frame.c
@@ -912,6 +912,12 @@ frame_unwind_register (struct frame_info *frame, int regnum, gdb_byte *buf)
 
   frame_register_unwind (frame, regnum, &optimized, &unavailable,
 			 &lval, &addr, &realnum, buf);
+
+  if (optimized)
+    error (_("Register %d was optimized out"), regnum);
+  if (unavailable)
+    throw_error (NOT_AVAILABLE_ERROR,
+		 _("Register %d is not available"), regnum);
 }
 
 void
@@ -1607,6 +1613,15 @@ get_prev_frame_1 (struct frame_info *this_frame)
   if (get_frame_type (this_frame) == INLINE_FRAME)
     return get_prev_frame_raw (this_frame);
 
+  /* Check that this frame is unwindable.  If it isn't, don't try to
+     unwind to the prev frame.  */
+  this_frame->stop_reason
+    = this_frame->unwind->stop_reason (this_frame,
+				       &this_frame->prologue_cache);
+
+  if (this_frame->stop_reason != UNWIND_NO_REASON)
+    return NULL;
+
   /* Check that this frame's ID was valid.  If it wasn't, don't try to
      unwind to the prev frame.  Be careful to not apply this test to
      the sentinel frame.  */
@@ -2333,6 +2348,9 @@ frame_stop_reason_string (enum unwind_stop_reason reason)
     case UNWIND_NULL_ID:
       return _("unwinder did not report frame ID");
 
+    case UNWIND_UNAVAILABLE:
+      return _("Not enough registers or memory available to unwind further");
+
     case UNWIND_INNER_ID:
       return _("previous frame inner to this frame (corrupt stack?)");
 
diff --git a/gdb/frame.h b/gdb/frame.h
index 7bc11480afd..a2052c030d7 100644
--- a/gdb/frame.h
+++ b/gdb/frame.h
@@ -457,12 +457,19 @@ enum unwind_stop_reason
        error.  But that's a project for another day.  */
     UNWIND_NULL_ID,
 
+    /* This frame is the outermost.  */
+    UNWIND_OUTERMOST,
+
     /* All the conditions after this point are considered errors;
        abnormal stack termination.  If a backtrace stops for one
        of these reasons, we'll let the user know.  This marker
        is not a valid stop reason.  */
     UNWIND_FIRST_ERROR,
 
+    /* Can't unwind further, because that would require knowing the
+       values of registers or memory that haven't been collected.  */
+    UNWIND_UNAVAILABLE,
+
     /* This frame ID looks like it ought to belong to a NEXT frame,
        but we got it for a PREV frame.  Normally, this is a sign of
        unwinder failure.  It could also indicate stack corruption.  */
diff --git a/gdb/frv-linux-tdep.c b/gdb/frv-linux-tdep.c
index 924a06b9828..b13554b743e 100644
--- a/gdb/frv-linux-tdep.c
+++ b/gdb/frv-linux-tdep.c
@@ -336,6 +336,7 @@ frv_linux_sigtramp_frame_sniffer (const struct frame_unwind *self,
 static const struct frame_unwind frv_linux_sigtramp_frame_unwind =
 {
   SIGTRAMP_FRAME,
+  default_frame_unwind_stop_reason,
   frv_linux_sigtramp_frame_this_id,
   frv_linux_sigtramp_frame_prev_register,
   NULL,
diff --git a/gdb/frv-tdep.c b/gdb/frv-tdep.c
index 66c25a854f2..98e64726fda 100644
--- a/gdb/frv-tdep.c
+++ b/gdb/frv-tdep.c
@@ -1494,6 +1494,7 @@ frv_frame_prev_register (struct frame_info *this_frame,
 
 static const struct frame_unwind frv_frame_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   frv_frame_this_id,
   frv_frame_prev_register,
   NULL,
diff --git a/gdb/h8300-tdep.c b/gdb/h8300-tdep.c
index 0b11df36d52..fa39dee36f5 100644
--- a/gdb/h8300-tdep.c
+++ b/gdb/h8300-tdep.c
@@ -526,6 +526,7 @@ h8300_frame_prev_register (struct frame_info *this_frame, void **this_cache,
 
 static const struct frame_unwind h8300_frame_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   h8300_frame_this_id,
   h8300_frame_prev_register,
   NULL,
diff --git a/gdb/hppa-hpux-tdep.c b/gdb/hppa-hpux-tdep.c
index b9761c36bd0..00ccf703b27 100644
--- a/gdb/hppa-hpux-tdep.c
+++ b/gdb/hppa-hpux-tdep.c
@@ -753,6 +753,7 @@ hppa_hpux_sigtramp_unwind_sniffer (const struct frame_unwind *self,
 
 static const struct frame_unwind hppa_hpux_sigtramp_frame_unwind = {
   SIGTRAMP_FRAME,
+  default_frame_unwind_stop_reason,
   hppa_hpux_sigtramp_frame_this_id,
   hppa_hpux_sigtramp_frame_prev_register,
   NULL,
diff --git a/gdb/hppa-linux-tdep.c b/gdb/hppa-linux-tdep.c
index 355f8f9d099..e51fbcc6340 100644
--- a/gdb/hppa-linux-tdep.c
+++ b/gdb/hppa-linux-tdep.c
@@ -314,6 +314,7 @@ hppa_linux_sigtramp_frame_sniffer (const struct frame_unwind *self,
 
 static const struct frame_unwind hppa_linux_sigtramp_frame_unwind = {
   SIGTRAMP_FRAME,
+  default_frame_unwind_stop_reason,
   hppa_linux_sigtramp_frame_this_id,
   hppa_linux_sigtramp_frame_prev_register,
   NULL,
diff --git a/gdb/hppa-tdep.c b/gdb/hppa-tdep.c
index df21faddcd3..b22e3c04e42 100644
--- a/gdb/hppa-tdep.c
+++ b/gdb/hppa-tdep.c
@@ -2225,6 +2225,7 @@ hppa_frame_unwind_sniffer (const struct frame_unwind *self,
 static const struct frame_unwind hppa_frame_unwind =
 {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   hppa_frame_this_id,
   hppa_frame_prev_register,
   NULL,
@@ -2335,6 +2336,7 @@ hppa_fallback_frame_prev_register (struct frame_info *this_frame,
 static const struct frame_unwind hppa_fallback_frame_unwind =
 {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   hppa_fallback_frame_this_id,
   hppa_fallback_frame_prev_register,
   NULL,
@@ -2431,6 +2433,7 @@ hppa_stub_unwind_sniffer (const struct frame_unwind *self,
 
 static const struct frame_unwind hppa_stub_frame_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   hppa_stub_frame_this_id,
   hppa_stub_frame_prev_register,
   NULL,
diff --git a/gdb/i386-tdep.c b/gdb/i386-tdep.c
index 62df6141ece..c7ad3a66074 100644
--- a/gdb/i386-tdep.c
+++ b/gdb/i386-tdep.c
@@ -45,7 +45,7 @@
 #include "dis-asm.h"
 #include "disasm.h"
 #include "remote.h"
-
+#include "exceptions.h"
 #include "gdb_assert.h"
 #include "gdb_string.h"
 
@@ -804,6 +804,7 @@ struct i386_frame_cache
 {
   /* Base address.  */
   CORE_ADDR base;
+  int base_p;
   LONGEST sp_offset;
   CORE_ADDR pc;
 
@@ -828,6 +829,7 @@ i386_alloc_frame_cache (void)
   cache = FRAME_OBSTACK_ZALLOC (struct i386_frame_cache);
 
   /* Base address.  */
+  cache->base_p = 0;
   cache->base = 0;
   cache->sp_offset = -4;
   cache->pc = 0;
@@ -1608,20 +1610,16 @@ i386_unwind_pc (struct gdbarch *gdbarch, struct frame_info *next_frame)
 
 /* Normal frames.  */
 
-static struct i386_frame_cache *
-i386_frame_cache (struct frame_info *this_frame, void **this_cache)
+static void
+i386_frame_cache_1 (struct frame_info *this_frame,
+		    struct i386_frame_cache *cache)
 {
   struct gdbarch *gdbarch = get_frame_arch (this_frame);
   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
-  struct i386_frame_cache *cache;
   gdb_byte buf[4];
   int i;
 
-  if (*this_cache)
-    return *this_cache;
-
-  cache = i386_alloc_frame_cache ();
-  *this_cache = cache;
+  cache->pc = get_frame_func (this_frame);
 
   /* In principle, for normal frames, %ebp holds the frame pointer,
      which holds the base address for the current stack frame.
@@ -1635,23 +1633,15 @@ i386_frame_cache (struct frame_info *this_frame, void **this_cache)
   get_frame_register (this_frame, I386_EBP_REGNUM, buf);
   cache->base = extract_unsigned_integer (buf, 4, byte_order);
   if (cache->base == 0)
-    return cache;
+    return;
 
   /* For normal frames, %eip is stored at 4(%ebp).  */
   cache->saved_regs[I386_EIP_REGNUM] = 4;
 
-  cache->pc = get_frame_func (this_frame);
   if (cache->pc != 0)
     i386_analyze_prologue (gdbarch, cache->pc, get_frame_pc (this_frame),
 			   cache);
 
-  if (cache->saved_sp_reg != -1)
-    {
-      /* Saved stack pointer has been saved.  */
-      get_frame_register (this_frame, cache->saved_sp_reg, buf);
-      cache->saved_sp = extract_unsigned_integer (buf, 4, byte_order);
-    }
-
   if (cache->locals < 0)
     {
       /* We didn't find a valid frame, which means that CACHE->base
@@ -1664,6 +1654,10 @@ i386_frame_cache (struct frame_info *this_frame, void **this_cache)
 
       if (cache->saved_sp_reg != -1)
 	{
+	  /* Saved stack pointer has been saved.  */
+	  get_frame_register (this_frame, cache->saved_sp_reg, buf);
+	  cache->saved_sp = extract_unsigned_integer (buf, 4, byte_order);
+
 	  /* We're halfway aligning the stack.  */
 	  cache->base = ((cache->saved_sp - 4) & 0xfffffff0) - 4;
 	  cache->saved_regs[I386_EIP_REGNUM] = cache->saved_sp - 4;
@@ -1691,9 +1685,17 @@ i386_frame_cache (struct frame_info *this_frame, void **this_cache)
 	cache->saved_regs[I386_EBP_REGNUM] = 0;
     }
 
+  if (cache->saved_sp_reg != -1)
+    {
+      /* Saved stack pointer has been saved (but the SAVED_SP_REG
+	 register may be unavailable).  */
+      if (cache->saved_sp == 0
+	  && frame_register_read (this_frame, cache->saved_sp_reg, buf))
+	cache->saved_sp = extract_unsigned_integer (buf, 4, byte_order);
+    }
   /* Now that we have the base address for the stack frame we can
      calculate the value of %esp in the calling frame.  */
-  if (cache->saved_sp == 0)
+  else if (cache->saved_sp == 0)
     cache->saved_sp = cache->base + 8;
 
   /* Adjust all the saved registers such that they contain addresses
@@ -1702,6 +1704,28 @@ i386_frame_cache (struct frame_info *this_frame, void **this_cache)
     if (cache->saved_regs[i] != -1)
       cache->saved_regs[i] += cache->base;
 
+  cache->base_p = 1;
+}
+
+static struct i386_frame_cache *
+i386_frame_cache (struct frame_info *this_frame, void **this_cache)
+{
+  volatile struct gdb_exception ex;
+  struct i386_frame_cache *cache;
+
+  if (*this_cache)
+    return *this_cache;
+
+  cache = i386_alloc_frame_cache ();
+  *this_cache = cache;
+
+  TRY_CATCH (ex, RETURN_MASK_ERROR)
+    {
+      i386_frame_cache_1 (this_frame, cache);
+    }
+  if (ex.reason < 0 && ex.error != NOT_AVAILABLE_ERROR)
+    throw_exception (ex);
+
   return cache;
 }
 
@@ -1719,6 +1743,22 @@ i386_frame_this_id (struct frame_info *this_frame, void **this_cache,
   (*this_id) = frame_id_build (cache->base + 8, cache->pc);
 }
 
+static enum unwind_stop_reason
+i386_frame_unwind_stop_reason (struct frame_info *this_frame,
+			       void **this_cache)
+{
+  struct i386_frame_cache *cache = i386_frame_cache (this_frame, this_cache);
+
+  if (!cache->base_p)
+    return UNWIND_UNAVAILABLE;
+
+  /* This marks the outermost frame.  */
+  if (cache->base == 0)
+    return UNWIND_OUTERMOST;
+
+  return UNWIND_NO_REASON;
+}
+
 static struct value *
 i386_frame_prev_register (struct frame_info *this_frame, void **this_cache,
 			  int regnum)
@@ -1758,8 +1798,18 @@ i386_frame_prev_register (struct frame_info *this_frame, void **this_cache,
   if (regnum == I386_EIP_REGNUM && cache->pc_in_eax)
     return frame_unwind_got_register (this_frame, regnum, I386_EAX_REGNUM);
 
-  if (regnum == I386_ESP_REGNUM && cache->saved_sp)
-    return frame_unwind_got_constant (this_frame, regnum, cache->saved_sp);
+  if (regnum == I386_ESP_REGNUM)
+    {
+      /* If the SP has been saved, but we don't know where, then this
+	 means that SAVED_SP_REG register was found unavailable back
+	 when we built the cache.  */
+      if (cache->saved_sp == 0 && cache->saved_sp_reg != -1)
+	return frame_unwind_got_register (this_frame, regnum,
+					  cache->saved_sp_reg);
+      else
+	return frame_unwind_got_constant (this_frame, regnum,
+					  cache->saved_sp);
+    }
 
   if (regnum < I386_NUM_SAVED_REGS && cache->saved_regs[regnum] != -1)
     return frame_unwind_got_memory (this_frame, regnum,
@@ -1771,6 +1821,7 @@ i386_frame_prev_register (struct frame_info *this_frame, void **this_cache,
 static const struct frame_unwind i386_frame_unwind =
 {
   NORMAL_FRAME,
+  i386_frame_unwind_stop_reason,
   i386_frame_this_id,
   i386_frame_prev_register,
   NULL,
@@ -1814,6 +1865,7 @@ i386_epilogue_frame_cache (struct frame_info *this_frame, void **this_cache)
 {
   struct gdbarch *gdbarch = get_frame_arch (this_frame);
   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
+  volatile struct gdb_exception ex;
   struct i386_frame_cache *cache;
   gdb_byte buf[4];
 
@@ -1823,23 +1875,43 @@ i386_epilogue_frame_cache (struct frame_info *this_frame, void **this_cache)
   cache = i386_alloc_frame_cache ();
   *this_cache = cache;
 
-  /* Cache base will be %esp plus cache->sp_offset (-4).  */
-  get_frame_register (this_frame, I386_ESP_REGNUM, buf);
-  cache->base = extract_unsigned_integer (buf, 4, 
-					  byte_order) + cache->sp_offset;
+  TRY_CATCH (ex, RETURN_MASK_ERROR)
+    {
+      /* Cache base will be %esp plus cache->sp_offset (-4).  */
+      get_frame_register (this_frame, I386_ESP_REGNUM, buf);
+      cache->base = extract_unsigned_integer (buf, 4,
+					      byte_order) + cache->sp_offset;
 
-  /* Cache pc will be the frame func.  */
-  cache->pc = get_frame_pc (this_frame);
+      /* Cache pc will be the frame func.  */
+      cache->pc = get_frame_pc (this_frame);
 
-  /* The saved %esp will be at cache->base plus 8.  */
-  cache->saved_sp = cache->base + 8;
+      /* The saved %esp will be at cache->base plus 8.  */
+      cache->saved_sp = cache->base + 8;
 
-  /* The saved %eip will be at cache->base plus 4.  */
-  cache->saved_regs[I386_EIP_REGNUM] = cache->base + 4;
+      /* The saved %eip will be at cache->base plus 4.  */
+      cache->saved_regs[I386_EIP_REGNUM] = cache->base + 4;
+
+      cache->base_p = 1;
+    }
+  if (ex.reason < 0 && ex.error != NOT_AVAILABLE_ERROR)
+    throw_exception (ex);
 
   return cache;
 }
 
+static enum unwind_stop_reason
+i386_epilogue_frame_unwind_stop_reason (struct frame_info *this_frame,
+					void **this_cache)
+{
+  struct i386_frame_cache *cache
+    = i386_epilogue_frame_cache (this_frame, this_cache);
+
+  if (!cache->base_p)
+    return UNWIND_UNAVAILABLE;
+
+  return UNWIND_NO_REASON;
+}
+
 static void
 i386_epilogue_frame_this_id (struct frame_info *this_frame,
 			     void **this_cache,
@@ -1848,12 +1920,16 @@ i386_epilogue_frame_this_id (struct frame_info *this_frame,
   struct i386_frame_cache *cache = i386_epilogue_frame_cache (this_frame,
 							      this_cache);
 
+  if (!cache->base_p)
+    return;
+
   (*this_id) = frame_id_build (cache->base + 8, cache->pc);
 }
 
 static const struct frame_unwind i386_epilogue_frame_unwind =
 {
   NORMAL_FRAME,
+  i386_epilogue_frame_unwind_stop_reason,
   i386_epilogue_frame_this_id,
   i386_frame_prev_register,
   NULL, 
@@ -1869,6 +1945,7 @@ i386_sigtramp_frame_cache (struct frame_info *this_frame, void **this_cache)
   struct gdbarch *gdbarch = get_frame_arch (this_frame);
   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
+  volatile struct gdb_exception ex;
   struct i386_frame_cache *cache;
   CORE_ADDR addr;
   gdb_byte buf[4];
@@ -1878,30 +1955,50 @@ i386_sigtramp_frame_cache (struct frame_info *this_frame, void **this_cache)
 
   cache = i386_alloc_frame_cache ();
 
-  get_frame_register (this_frame, I386_ESP_REGNUM, buf);
-  cache->base = extract_unsigned_integer (buf, 4, byte_order) - 4;
-
-  addr = tdep->sigcontext_addr (this_frame);
-  if (tdep->sc_reg_offset)
+  TRY_CATCH (ex, RETURN_MASK_ERROR)
     {
-      int i;
+      get_frame_register (this_frame, I386_ESP_REGNUM, buf);
+      cache->base = extract_unsigned_integer (buf, 4, byte_order) - 4;
 
-      gdb_assert (tdep->sc_num_regs <= I386_NUM_SAVED_REGS);
+      addr = tdep->sigcontext_addr (this_frame);
+      if (tdep->sc_reg_offset)
+	{
+	  int i;
 
-      for (i = 0; i < tdep->sc_num_regs; i++)
-	if (tdep->sc_reg_offset[i] != -1)
-	  cache->saved_regs[i] = addr + tdep->sc_reg_offset[i];
-    }
-  else
-    {
-      cache->saved_regs[I386_EIP_REGNUM] = addr + tdep->sc_pc_offset;
-      cache->saved_regs[I386_ESP_REGNUM] = addr + tdep->sc_sp_offset;
+	  gdb_assert (tdep->sc_num_regs <= I386_NUM_SAVED_REGS);
+
+	  for (i = 0; i < tdep->sc_num_regs; i++)
+	    if (tdep->sc_reg_offset[i] != -1)
+	      cache->saved_regs[i] = addr + tdep->sc_reg_offset[i];
+	}
+      else
+	{
+	  cache->saved_regs[I386_EIP_REGNUM] = addr + tdep->sc_pc_offset;
+	  cache->saved_regs[I386_ESP_REGNUM] = addr + tdep->sc_sp_offset;
+	}
+
+      cache->base_p = 1;
     }
+  if (ex.reason < 0 && ex.error != NOT_AVAILABLE_ERROR)
+    throw_exception (ex);
 
   *this_cache = cache;
   return cache;
 }
 
+static enum unwind_stop_reason
+i386_sigtramp_frame_unwind_stop_reason (struct frame_info *this_frame,
+					void **this_cache)
+{
+  struct i386_frame_cache *cache =
+    i386_sigtramp_frame_cache (this_frame, this_cache);
+
+  if (!cache->base_p)
+    return UNWIND_UNAVAILABLE;
+
+  return UNWIND_NO_REASON;
+}
+
 static void
 i386_sigtramp_frame_this_id (struct frame_info *this_frame, void **this_cache,
 			     struct frame_id *this_id)
@@ -1909,6 +2006,9 @@ i386_sigtramp_frame_this_id (struct frame_info *this_frame, void **this_cache,
   struct i386_frame_cache *cache =
     i386_sigtramp_frame_cache (this_frame, this_cache);
 
+  if (!cache->base_p)
+    return;
+
   /* See the end of i386_push_dummy_call.  */
   (*this_id) = frame_id_build (cache->base + 8, get_frame_pc (this_frame));
 }
@@ -1956,6 +2056,7 @@ i386_sigtramp_frame_sniffer (const struct frame_unwind *self,
 static const struct frame_unwind i386_sigtramp_frame_unwind =
 {
   SIGTRAMP_FRAME,
+  i386_sigtramp_frame_unwind_stop_reason,
   i386_sigtramp_frame_this_id,
   i386_sigtramp_frame_prev_register,
   NULL,
diff --git a/gdb/i386obsd-tdep.c b/gdb/i386obsd-tdep.c
index 842215fb8f8..480aa0cf5e4 100644
--- a/gdb/i386obsd-tdep.c
+++ b/gdb/i386obsd-tdep.c
@@ -434,6 +434,7 @@ static const struct frame_unwind i386obsd_trapframe_unwind = {
      frame, but SIGTRAMP_FRAME would print <signal handler called>,
      which really is not what we want here.  */
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   i386obsd_trapframe_this_id,
   i386obsd_trapframe_prev_register,
   NULL,
diff --git a/gdb/ia64-tdep.c b/gdb/ia64-tdep.c
index 363800dbf29..68e50217028 100644
--- a/gdb/ia64-tdep.c
+++ b/gdb/ia64-tdep.c
@@ -2175,6 +2175,7 @@ ia64_frame_prev_register (struct frame_info *this_frame, void **this_cache,
 static const struct frame_unwind ia64_frame_unwind =
 {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   &ia64_frame_this_id,
   &ia64_frame_prev_register,
   NULL,
@@ -2366,6 +2367,7 @@ ia64_sigtramp_frame_sniffer (const struct frame_unwind *self,
 static const struct frame_unwind ia64_sigtramp_frame_unwind =
 {
   SIGTRAMP_FRAME,
+  default_frame_unwind_stop_reason,
   ia64_sigtramp_frame_this_id,
   ia64_sigtramp_frame_prev_register,
   NULL,
@@ -3051,6 +3053,7 @@ ia64_libunwind_frame_sniffer (const struct frame_unwind *self,
 static const struct frame_unwind ia64_libunwind_frame_unwind =
 {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   ia64_libunwind_frame_this_id,
   ia64_libunwind_frame_prev_register,
   NULL,
@@ -3139,6 +3142,7 @@ ia64_libunwind_sigtramp_frame_sniffer (const struct frame_unwind *self,
 static const struct frame_unwind ia64_libunwind_sigtramp_frame_unwind =
 {
   SIGTRAMP_FRAME,
+  default_frame_unwind_stop_reason,
   ia64_libunwind_sigtramp_frame_this_id,
   ia64_libunwind_sigtramp_frame_prev_register,
   NULL,
diff --git a/gdb/inline-frame.c b/gdb/inline-frame.c
index 7554fc76000..dc05b8a3449 100644
--- a/gdb/inline-frame.c
+++ b/gdb/inline-frame.c
@@ -260,6 +260,7 @@ inline_frame_sniffer (const struct frame_unwind *self,
 
 const struct frame_unwind inline_frame_unwind = {
   INLINE_FRAME,
+  default_frame_unwind_stop_reason,
   inline_frame_this_id,
   inline_frame_prev_register,
   NULL,
diff --git a/gdb/iq2000-tdep.c b/gdb/iq2000-tdep.c
index 2e54478069a..1926da60b39 100644
--- a/gdb/iq2000-tdep.c
+++ b/gdb/iq2000-tdep.c
@@ -436,6 +436,7 @@ iq2000_frame_this_id (struct frame_info *this_frame, void **this_cache,
 
 static const struct frame_unwind iq2000_frame_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   iq2000_frame_this_id,
   iq2000_frame_prev_register,
   NULL,
diff --git a/gdb/lm32-tdep.c b/gdb/lm32-tdep.c
index 327ac327d8a..d05b3b81a84 100644
--- a/gdb/lm32-tdep.c
+++ b/gdb/lm32-tdep.c
@@ -496,6 +496,7 @@ lm32_frame_prev_register (struct frame_info *this_frame,
 
 static const struct frame_unwind lm32_frame_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   lm32_frame_this_id,
   lm32_frame_prev_register,
   NULL,
diff --git a/gdb/m32c-tdep.c b/gdb/m32c-tdep.c
index 454a4b681c2..673e40cb416 100644
--- a/gdb/m32c-tdep.c
+++ b/gdb/m32c-tdep.c
@@ -1960,6 +1960,7 @@ m32c_prev_register (struct frame_info *this_frame,
 
 static const struct frame_unwind m32c_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   m32c_this_id,
   m32c_prev_register,
   NULL,
diff --git a/gdb/m32r-linux-tdep.c b/gdb/m32r-linux-tdep.c
index 1339a872d21..a7efe612dec 100644
--- a/gdb/m32r-linux-tdep.c
+++ b/gdb/m32r-linux-tdep.c
@@ -305,6 +305,7 @@ m32r_linux_sigtramp_frame_sniffer (const struct frame_unwind *self,
 
 static const struct frame_unwind m32r_linux_sigtramp_frame_unwind = {
   SIGTRAMP_FRAME,
+  default_frame_unwind_stop_reason,
   m32r_linux_sigtramp_frame_this_id,
   m32r_linux_sigtramp_frame_prev_register,
   NULL,
diff --git a/gdb/m32r-tdep.c b/gdb/m32r-tdep.c
index 659c3c87487..136fd7bc65d 100644
--- a/gdb/m32r-tdep.c
+++ b/gdb/m32r-tdep.c
@@ -876,6 +876,7 @@ m32r_frame_prev_register (struct frame_info *this_frame,
 
 static const struct frame_unwind m32r_frame_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   m32r_frame_this_id,
   m32r_frame_prev_register,
   NULL,
diff --git a/gdb/m68hc11-tdep.c b/gdb/m68hc11-tdep.c
index ced6eabb520..b789ce72c87 100644
--- a/gdb/m68hc11-tdep.c
+++ b/gdb/m68hc11-tdep.c
@@ -949,6 +949,7 @@ m68hc11_frame_prev_register (struct frame_info *this_frame,
 
 static const struct frame_unwind m68hc11_frame_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   m68hc11_frame_this_id,
   m68hc11_frame_prev_register,
   NULL,
diff --git a/gdb/m68k-tdep.c b/gdb/m68k-tdep.c
index 2706969dac5..6d7a824f79c 100644
--- a/gdb/m68k-tdep.c
+++ b/gdb/m68k-tdep.c
@@ -976,6 +976,7 @@ m68k_frame_prev_register (struct frame_info *this_frame, void **this_cache,
 static const struct frame_unwind m68k_frame_unwind =
 {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   m68k_frame_this_id,
   m68k_frame_prev_register,
   NULL,
diff --git a/gdb/m68klinux-tdep.c b/gdb/m68klinux-tdep.c
index b95fad566da..c3513bcd182 100644
--- a/gdb/m68klinux-tdep.c
+++ b/gdb/m68klinux-tdep.c
@@ -328,6 +328,7 @@ m68k_linux_sigtramp_frame_sniffer (const struct frame_unwind *self,
 static const struct frame_unwind m68k_linux_sigtramp_frame_unwind =
 {
   SIGTRAMP_FRAME,
+  default_frame_unwind_stop_reason,
   m68k_linux_sigtramp_frame_this_id,
   m68k_linux_sigtramp_frame_prev_register,
   NULL,
diff --git a/gdb/m88k-tdep.c b/gdb/m88k-tdep.c
index 76dcbe14018..1e4c546b0ae 100644
--- a/gdb/m88k-tdep.c
+++ b/gdb/m88k-tdep.c
@@ -749,6 +749,7 @@ m88k_frame_prev_register (struct frame_info *this_frame,
 static const struct frame_unwind m88k_frame_unwind =
 {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   m88k_frame_this_id,
   m88k_frame_prev_register,
   NULL,
diff --git a/gdb/mep-tdep.c b/gdb/mep-tdep.c
index dd5a4a541b3..bc40b9980ec 100644
--- a/gdb/mep-tdep.c
+++ b/gdb/mep-tdep.c
@@ -2094,6 +2094,7 @@ mep_frame_prev_register (struct frame_info *this_frame,
 
 static const struct frame_unwind mep_frame_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   mep_frame_this_id,
   mep_frame_prev_register,
   NULL,
diff --git a/gdb/microblaze-tdep.c b/gdb/microblaze-tdep.c
index 1e994a2d6cf..2482c87f48d 100644
--- a/gdb/microblaze-tdep.c
+++ b/gdb/microblaze-tdep.c
@@ -521,6 +521,7 @@ microblaze_frame_prev_register (struct frame_info *this_frame,
 static const struct frame_unwind microblaze_frame_unwind =
 {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   microblaze_frame_this_id,
   microblaze_frame_prev_register,
   NULL,
diff --git a/gdb/mips-tdep.c b/gdb/mips-tdep.c
index e5aed94c578..47d9182b02d 100644
--- a/gdb/mips-tdep.c
+++ b/gdb/mips-tdep.c
@@ -2028,6 +2028,7 @@ mips_insn16_frame_sniffer (const struct frame_unwind *self,
 static const struct frame_unwind mips_insn16_frame_unwind =
 {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   mips_insn16_frame_this_id,
   mips_insn16_frame_prev_register,
   NULL,
@@ -2381,6 +2382,7 @@ mips_insn32_frame_sniffer (const struct frame_unwind *self,
 static const struct frame_unwind mips_insn32_frame_unwind =
 {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   mips_insn32_frame_this_id,
   mips_insn32_frame_prev_register,
   NULL,
@@ -2505,6 +2507,7 @@ mips_stub_frame_sniffer (const struct frame_unwind *self,
 static const struct frame_unwind mips_stub_frame_unwind =
 {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   mips_stub_frame_this_id,
   mips_stub_frame_prev_register,
   NULL,
diff --git a/gdb/mn10300-tdep.c b/gdb/mn10300-tdep.c
index 5b83b226a3d..e949b403b7a 100644
--- a/gdb/mn10300-tdep.c
+++ b/gdb/mn10300-tdep.c
@@ -1174,6 +1174,7 @@ mn10300_frame_prev_register (struct frame_info *this_frame,
 
 static const struct frame_unwind mn10300_frame_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   mn10300_frame_this_id, 
   mn10300_frame_prev_register,
   NULL,
diff --git a/gdb/moxie-tdep.c b/gdb/moxie-tdep.c
index 84d495fcfb6..5fb3d108baa 100644
--- a/gdb/moxie-tdep.c
+++ b/gdb/moxie-tdep.c
@@ -461,6 +461,7 @@ moxie_frame_prev_register (struct frame_info *this_frame,
 
 static const struct frame_unwind moxie_frame_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   moxie_frame_this_id,
   moxie_frame_prev_register,
   NULL,
diff --git a/gdb/mt-tdep.c b/gdb/mt-tdep.c
index 9b0971f7626..ee98d3d25ca 100644
--- a/gdb/mt-tdep.c
+++ b/gdb/mt-tdep.c
@@ -1115,6 +1115,7 @@ mt_frame_base_address (struct frame_info *this_frame,
 
 static const struct frame_unwind mt_frame_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   mt_frame_this_id,
   mt_frame_prev_register,
   NULL,
diff --git a/gdb/ppc-linux-tdep.c b/gdb/ppc-linux-tdep.c
index ba70ffdd988..c6e4b838c09 100644
--- a/gdb/ppc-linux-tdep.c
+++ b/gdb/ppc-linux-tdep.c
@@ -1472,6 +1472,7 @@ ppu2spu_dealloc_cache (struct frame_info *self, void *this_cache)
 
 static const struct frame_unwind ppu2spu_unwind = {
   ARCH_FRAME,
+  default_frame_unwind_stop_reason,
   ppu2spu_this_id,
   ppu2spu_prev_register,
   NULL,
diff --git a/gdb/ppcobsd-tdep.c b/gdb/ppcobsd-tdep.c
index 51cb639dc2d..d4e2d792e02 100644
--- a/gdb/ppcobsd-tdep.c
+++ b/gdb/ppcobsd-tdep.c
@@ -239,6 +239,7 @@ ppcobsd_sigtramp_frame_prev_register (struct frame_info *this_frame,
 
 static const struct frame_unwind ppcobsd_sigtramp_frame_unwind = {
   SIGTRAMP_FRAME,
+  default_frame_unwind_stop_reason,
   ppcobsd_sigtramp_frame_this_id,
   ppcobsd_sigtramp_frame_prev_register,
   NULL,
diff --git a/gdb/rs6000-tdep.c b/gdb/rs6000-tdep.c
index 23fe9e336fe..653964430f0 100644
--- a/gdb/rs6000-tdep.c
+++ b/gdb/rs6000-tdep.c
@@ -3319,6 +3319,7 @@ rs6000_frame_prev_register (struct frame_info *this_frame,
 static const struct frame_unwind rs6000_frame_unwind =
 {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   rs6000_frame_this_id,
   rs6000_frame_prev_register,
   NULL,
diff --git a/gdb/s390-tdep.c b/gdb/s390-tdep.c
index d74bbf05814..d9407efeb83 100644
--- a/gdb/s390-tdep.c
+++ b/gdb/s390-tdep.c
@@ -1758,6 +1758,7 @@ s390_frame_prev_register (struct frame_info *this_frame,
 
 static const struct frame_unwind s390_frame_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   s390_frame_this_id,
   s390_frame_prev_register,
   NULL,
@@ -1841,6 +1842,7 @@ s390_stub_frame_sniffer (const struct frame_unwind *self,
 
 static const struct frame_unwind s390_stub_frame_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   s390_stub_frame_this_id,
   s390_stub_frame_prev_register,
   NULL,
@@ -2032,6 +2034,7 @@ s390_sigtramp_frame_sniffer (const struct frame_unwind *self,
 
 static const struct frame_unwind s390_sigtramp_frame_unwind = {
   SIGTRAMP_FRAME,
+  default_frame_unwind_stop_reason,
   s390_sigtramp_frame_this_id,
   s390_sigtramp_frame_prev_register,
   NULL,
diff --git a/gdb/score-tdep.c b/gdb/score-tdep.c
index ffe562fa341..4ddcd2773cd 100644
--- a/gdb/score-tdep.c
+++ b/gdb/score-tdep.c
@@ -1369,6 +1369,7 @@ score_prologue_prev_register (struct frame_info *this_frame,
 static const struct frame_unwind score_prologue_unwind =
 {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   score_prologue_this_id,
   score_prologue_prev_register,
   NULL,
diff --git a/gdb/sentinel-frame.c b/gdb/sentinel-frame.c
index e6000cc136c..6c2f3e079d1 100644
--- a/gdb/sentinel-frame.c
+++ b/gdb/sentinel-frame.c
@@ -51,9 +51,10 @@ sentinel_frame_prev_register (struct frame_info *this_frame,
   struct gdbarch *gdbarch = get_frame_arch (this_frame);
   struct frame_unwind_cache *cache = *this_prologue_cache;
   struct value *value;
+  struct type *regtype = register_type (gdbarch, regnum);
 
   /* Return the actual value.  */
-  value = allocate_value (register_type (gdbarch, regnum));
+  value = allocate_value (regtype);
   VALUE_LVAL (value) = lval_register;
   VALUE_REGNUM (value) = regnum;
   VALUE_FRAME_ID (value) = get_frame_id (this_frame);
@@ -64,7 +65,7 @@ sentinel_frame_prev_register (struct frame_info *this_frame,
   if (regcache_cooked_read (cache->regcache,
 			    regnum,
 			    value_contents_raw (value)) == REG_UNAVAILABLE)
-    mark_value_bytes_unavailable (value, 0, register_size (gdbarch, regnum));
+    mark_value_bytes_unavailable (value, 0, TYPE_LENGTH (regtype));
 
   return value;
 }
@@ -92,6 +93,7 @@ sentinel_frame_prev_arch (struct frame_info *this_frame,
 const struct frame_unwind sentinel_frame_unwind =
 {
   SENTINEL_FRAME,
+  default_frame_unwind_stop_reason,
   sentinel_frame_this_id,
   sentinel_frame_prev_register,
   NULL,
diff --git a/gdb/sh-tdep.c b/gdb/sh-tdep.c
index 49ef8c64a0f..e713cee2cfc 100644
--- a/gdb/sh-tdep.c
+++ b/gdb/sh-tdep.c
@@ -2635,6 +2635,7 @@ sh_frame_this_id (struct frame_info *this_frame, void **this_cache,
 
 static const struct frame_unwind sh_frame_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   sh_frame_this_id,
   sh_frame_prev_register,
   NULL,
diff --git a/gdb/sh64-tdep.c b/gdb/sh64-tdep.c
index dca560a1c56..a4da7a4d30d 100644
--- a/gdb/sh64-tdep.c
+++ b/gdb/sh64-tdep.c
@@ -2437,6 +2437,7 @@ sh64_frame_this_id (struct frame_info *this_frame, void **this_cache,
 
 static const struct frame_unwind sh64_frame_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   sh64_frame_this_id,
   sh64_frame_prev_register,
   NULL,
diff --git a/gdb/sparc-sol2-tdep.c b/gdb/sparc-sol2-tdep.c
index ee9d9b52661..a49eb7f36b1 100644
--- a/gdb/sparc-sol2-tdep.c
+++ b/gdb/sparc-sol2-tdep.c
@@ -164,6 +164,7 @@ sparc32_sol2_sigtramp_frame_sniffer (const struct frame_unwind *self,
 static const struct frame_unwind sparc32_sol2_sigtramp_frame_unwind =
 {
   SIGTRAMP_FRAME,
+  default_frame_unwind_stop_reason,
   sparc32_sol2_sigtramp_frame_this_id,
   sparc32_sol2_sigtramp_frame_prev_register,
   NULL,
diff --git a/gdb/sparc-tdep.c b/gdb/sparc-tdep.c
index 90817c9caf6..1039bd8e768 100644
--- a/gdb/sparc-tdep.c
+++ b/gdb/sparc-tdep.c
@@ -1031,6 +1031,7 @@ sparc32_frame_prev_register (struct frame_info *this_frame,
 static const struct frame_unwind sparc32_frame_unwind =
 {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   sparc32_frame_this_id,
   sparc32_frame_prev_register,
   NULL,
diff --git a/gdb/sparc64-sol2-tdep.c b/gdb/sparc64-sol2-tdep.c
index a50943f572e..d11619d8691 100644
--- a/gdb/sparc64-sol2-tdep.c
+++ b/gdb/sparc64-sol2-tdep.c
@@ -141,6 +141,7 @@ sparc64_sol2_sigtramp_frame_sniffer (const struct frame_unwind *self,
 static const struct frame_unwind sparc64_sol2_sigtramp_frame_unwind =
 {
   SIGTRAMP_FRAME,
+  default_frame_unwind_stop_reason,
   sparc64_sol2_sigtramp_frame_this_id,
   sparc64_sol2_sigtramp_frame_prev_register,
   NULL,
diff --git a/gdb/sparc64-tdep.c b/gdb/sparc64-tdep.c
index 4b42f01556b..674d390bdb3 100644
--- a/gdb/sparc64-tdep.c
+++ b/gdb/sparc64-tdep.c
@@ -562,6 +562,7 @@ sparc64_frame_prev_register (struct frame_info *this_frame, void **this_cache,
 static const struct frame_unwind sparc64_frame_unwind =
 {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   sparc64_frame_this_id,
   sparc64_frame_prev_register,
   NULL,
diff --git a/gdb/sparc64fbsd-tdep.c b/gdb/sparc64fbsd-tdep.c
index 36a117711f0..49d30503384 100644
--- a/gdb/sparc64fbsd-tdep.c
+++ b/gdb/sparc64fbsd-tdep.c
@@ -202,6 +202,7 @@ sparc64fbsd_sigtramp_frame_sniffer (const struct frame_unwind *self,
 static const struct frame_unwind sparc64fbsd_sigtramp_frame_unwind =
 {
   SIGTRAMP_FRAME,
+  default_frame_unwind_stop_reason,
   sparc64fbsd_sigtramp_frame_this_id,
   sparc64fbsd_sigtramp_frame_prev_register,
   NULL,
diff --git a/gdb/sparc64nbsd-tdep.c b/gdb/sparc64nbsd-tdep.c
index 12818d01a9f..5d6c27c17f4 100644
--- a/gdb/sparc64nbsd-tdep.c
+++ b/gdb/sparc64nbsd-tdep.c
@@ -230,6 +230,7 @@ sparc64nbsd_sigtramp_frame_sniffer (const struct frame_unwind *self,
 static const struct frame_unwind sparc64nbsd_sigcontext_frame_unwind =
 {
   SIGTRAMP_FRAME,
+  default_frame_unwind_stop_reason,
   sparc64nbsd_sigcontext_frame_this_id,
   sparc64nbsd_sigcontext_frame_prev_register,
   NULL,
diff --git a/gdb/sparc64obsd-tdep.c b/gdb/sparc64obsd-tdep.c
index 226f277b5b7..adc16a18a45 100644
--- a/gdb/sparc64obsd-tdep.c
+++ b/gdb/sparc64obsd-tdep.c
@@ -195,6 +195,7 @@ sparc64obsd_sigtramp_frame_sniffer (const struct frame_unwind *self,
 static const struct frame_unwind sparc64obsd_frame_unwind =
 {
   SIGTRAMP_FRAME,
+  default_frame_unwind_stop_reason,
   sparc64obsd_frame_this_id,
   sparc64obsd_frame_prev_register,
   NULL,
@@ -277,6 +278,7 @@ sparc64obsd_trapframe_sniffer (const struct frame_unwind *self,
 static const struct frame_unwind sparc64obsd_trapframe_unwind =
 {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   sparc64obsd_trapframe_this_id,
   sparc64obsd_trapframe_prev_register,
   NULL,
diff --git a/gdb/sparcnbsd-tdep.c b/gdb/sparcnbsd-tdep.c
index 03eb1ef4739..8bbaa4bc9da 100644
--- a/gdb/sparcnbsd-tdep.c
+++ b/gdb/sparcnbsd-tdep.c
@@ -254,6 +254,7 @@ sparc32nbsd_sigcontext_frame_sniffer (const struct frame_unwind *self,
 static const struct frame_unwind sparc32nbsd_sigcontext_frame_unwind =
 {
   SIGTRAMP_FRAME,
+  default_frame_unwind_stop_reason,
   sparc32nbsd_sigcontext_frame_this_id,
   sparc32nbsd_sigcontext_frame_prev_register,
   NULL,
diff --git a/gdb/sparcobsd-tdep.c b/gdb/sparcobsd-tdep.c
index 6a3c43cb74f..b9e954001a4 100644
--- a/gdb/sparcobsd-tdep.c
+++ b/gdb/sparcobsd-tdep.c
@@ -139,6 +139,7 @@ sparc32obsd_sigtramp_frame_sniffer (const struct frame_unwind *self,
 static const struct frame_unwind sparc32obsd_sigtramp_frame_unwind =
 {
   SIGTRAMP_FRAME,
+  default_frame_unwind_stop_reason,
   sparc32obsd_sigtramp_frame_this_id,
   sparc32obsd_sigtramp_frame_prev_register,
   NULL,
diff --git a/gdb/spu-tdep.c b/gdb/spu-tdep.c
index da7024a0b39..7f2079474e6 100644
--- a/gdb/spu-tdep.c
+++ b/gdb/spu-tdep.c
@@ -1082,6 +1082,7 @@ spu_frame_prev_register (struct frame_info *this_frame,
 
 static const struct frame_unwind spu_frame_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   spu_frame_this_id,
   spu_frame_prev_register,
   NULL,
@@ -1236,6 +1237,7 @@ spu2ppu_dealloc_cache (struct frame_info *self, void *this_cache)
 
 static const struct frame_unwind spu2ppu_unwind = {
   ARCH_FRAME,
+  default_frame_unwind_stop_reason,
   spu2ppu_this_id,
   spu2ppu_prev_register,
   NULL,
diff --git a/gdb/v850-tdep.c b/gdb/v850-tdep.c
index 620536f1f82..96e8d22c6ed 100644
--- a/gdb/v850-tdep.c
+++ b/gdb/v850-tdep.c
@@ -935,6 +935,7 @@ v850_frame_this_id (struct frame_info *this_frame, void **this_cache,
 
 static const struct frame_unwind v850_frame_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   v850_frame_this_id,
   v850_frame_prev_register,
   NULL,
diff --git a/gdb/vax-tdep.c b/gdb/vax-tdep.c
index b84977a5d1e..97d453452d6 100644
--- a/gdb/vax-tdep.c
+++ b/gdb/vax-tdep.c
@@ -402,6 +402,7 @@ vax_frame_prev_register (struct frame_info *this_frame,
 static const struct frame_unwind vax_frame_unwind =
 {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   vax_frame_this_id,
   vax_frame_prev_register,
   NULL,
diff --git a/gdb/vaxobsd-tdep.c b/gdb/vaxobsd-tdep.c
index f87f2325542..7089f1532cb 100644
--- a/gdb/vaxobsd-tdep.c
+++ b/gdb/vaxobsd-tdep.c
@@ -135,6 +135,7 @@ vaxobsd_sigtramp_frame_prev_register (struct frame_info *this_frame,
 
 static const struct frame_unwind vaxobsd_sigtramp_frame_unwind = {
   SIGTRAMP_FRAME,
+  default_frame_unwind_stop_reason,
   vaxobsd_sigtramp_frame_this_id,
   vaxobsd_sigtramp_frame_prev_register,
   NULL,
diff --git a/gdb/xstormy16-tdep.c b/gdb/xstormy16-tdep.c
index 1aef08a8eee..53cbecdf9b6 100644
--- a/gdb/xstormy16-tdep.c
+++ b/gdb/xstormy16-tdep.c
@@ -742,6 +742,7 @@ xstormy16_frame_base_address (struct frame_info *this_frame, void **this_cache)
 
 static const struct frame_unwind xstormy16_frame_unwind = {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   xstormy16_frame_this_id,
   xstormy16_frame_prev_register,
   NULL,
diff --git a/gdb/xtensa-tdep.c b/gdb/xtensa-tdep.c
index 316a8cf5194..24cc79c42bd 100644
--- a/gdb/xtensa-tdep.c
+++ b/gdb/xtensa-tdep.c
@@ -1549,6 +1549,7 @@ static const struct frame_unwind
 xtensa_unwind =
 {
   NORMAL_FRAME,
+  default_frame_unwind_stop_reason,
   xtensa_frame_this_id,
   xtensa_frame_prev_register,
   NULL,