Import LLVM libunwind snapshot revision 272680vendor/llvm-libunwind/libunwind-r272680

Significant upstream revisions:

260595: [AArch64] Fix libunwind build when using GNU assembler
270692: Introduce a native-only unwinder build.
270972: Disable cross-unwinding by default.
271004: [libunwind] Improve unwinder stack usage - II
272680: [libunwind] Improve unwinder stack usage - III

Obtained from:	https://llvm.org/svn/llvm-project/libunwind/trunk/

12 files changed, 239 insertions, 173 deletions

diff --git a/include/__libunwind_config.h b/include/__libunwind_config.h
index 63393d3058e8..099d133e744b 100644
--- a/include/__libunwind_config.h
+++ b/include/__libunwind_config.h
@@ -17,4 +17,43 @@
 #define _LIBUNWIND_ARM_EHABI 0
 #endif
 
+#if defined(_LIBUNWIND_IS_NATIVE_ONLY)
+# if defined(__i386__)
+#  define _LIBUNWIND_TARGET_I386 1
+#  define _LIBUNWIND_CONTEXT_SIZE 8
+#  define _LIBUNWIND_CURSOR_SIZE 19
+# elif defined(__x86_64__)
+#  define _LIBUNWIND_TARGET_X86_64 1
+#  define _LIBUNWIND_CONTEXT_SIZE 21
+#  define _LIBUNWIND_CURSOR_SIZE 33
+# elif defined(__ppc__)
+#  define _LIBUNWIND_TARGET_PPC 1
+#  define _LIBUNWIND_CONTEXT_SIZE 117
+#  define _LIBUNWIND_CURSOR_SIZE 128
+# elif defined(__aarch64__)
+#  define _LIBUNWIND_TARGET_AARCH64 1
+#  define _LIBUNWIND_CONTEXT_SIZE 66
+#  define _LIBUNWIND_CURSOR_SIZE 78
+# elif defined(__arm__)
+#  define _LIBUNWIND_TARGET_ARM 1
+#  define _LIBUNWIND_CONTEXT_SIZE 60
+#  define _LIBUNWIND_CURSOR_SIZE 67
+# elif defined(__or1k__)
+#  define _LIBUNWIND_TARGET_OR1K 1
+#  define _LIBUNWIND_CONTEXT_SIZE 16
+#  define _LIBUNWIND_CURSOR_SIZE 28
+# else
+#  error "Unsupported architecture."
+# endif
+#else // !_LIBUNWIND_IS_NATIVE_ONLY
+# define _LIBUNWIND_TARGET_I386 1
+# define _LIBUNWIND_TARGET_X86_64 1
+# define _LIBUNWIND_TARGET_PPC 1
+# define _LIBUNWIND_TARGET_AARCH64 1
+# define _LIBUNWIND_TARGET_ARM 1
+# define _LIBUNWIND_TARGET_OR1K 1
+# define _LIBUNWIND_CONTEXT_SIZE 128
+# define _LIBUNWIND_CURSOR_SIZE 140
+#endif // _LIBUNWIND_IS_NATIVE_ONLY
+
 #endif // ____LIBUNWIND_CONFIG_H__
diff --git a/include/libunwind.h b/include/libunwind.h
index 6045becc01aa..c5b9633b1506 100644
--- a/include/libunwind.h
+++ b/include/libunwind.h
@@ -46,12 +46,12 @@ enum {
 };
 
 struct unw_context_t {
-  uint64_t data[128];
+  uint64_t data[_LIBUNWIND_CONTEXT_SIZE];
 };
 typedef struct unw_context_t unw_context_t;
 
 struct unw_cursor_t {
-  uint64_t data[140];
+  uint64_t data[_LIBUNWIND_CURSOR_SIZE];
 };
 typedef struct unw_cursor_t unw_cursor_t;
 
diff --git a/src/AddressSpace.hpp b/src/AddressSpace.hpp
index 73013c73ff71..da1b6a43e492 100644
--- a/src/AddressSpace.hpp
+++ b/src/AddressSpace.hpp
@@ -35,7 +35,7 @@ namespace libunwind {
 #include "Registers.hpp"
 
 #if _LIBUNWIND_ARM_EHABI
-#if defined(__FreeBSD__)
+#if defined(__FreeBSD__) || defined(__NetBSD__)
 
 typedef void *_Unwind_Ptr;
 
@@ -61,7 +61,8 @@ extern EHTEntry __exidx_end;
 #endif // !defined(_LIBUNWIND_IS_BAREMETAL)
 #endif // _LIBUNWIND_ARM_EHABI
 
-#if defined(__CloudABI__) || defined(__FreeBSD__) || defined(__linux__)
+#if defined(__CloudABI__) || defined(__FreeBSD__) || defined(__linux__) ||	\
+    defined(__NetBSD__)
 #if _LIBUNWIND_SUPPORT_DWARF_UNWIND && _LIBUNWIND_SUPPORT_DWARF_INDEX
 #include <link.h>
 // Macro for machine-independent access to the ELF program headers. This
diff --git a/src/CompactUnwinder.hpp b/src/CompactUnwinder.hpp
index cd9ce3e5ecd8..f528fba984db 100644
--- a/src/CompactUnwinder.hpp
+++ b/src/CompactUnwinder.hpp
@@ -27,6 +27,7 @@
 
 namespace libunwind {
 
+#if defined(_LIBUNWIND_TARGET_I386)
 /// CompactUnwinder_x86 uses a compact unwind info to virtually "step" (aka
 /// unwind) by modifying a Registers_x86 register set
 template <typename A>
@@ -255,8 +256,10 @@ void CompactUnwinder_x86<A>::framelessUnwind(
   // old esp is before return address
   registers.setSP((uint32_t)returnAddressLocation + 4);
 }
+#endif // _LIBUNWIND_TARGET_I386
 
 
+#if defined(_LIBUNWIND_TARGET_X86_64)
 /// CompactUnwinder_x86_64 uses a compact unwind info to virtually "step" (aka
 /// unwind) by modifying a Registers_x86_64 register set
 template <typename A>
@@ -484,9 +487,11 @@ void CompactUnwinder_x86_64<A>::framelessUnwind(A &addressSpace,
   // old esp is before return address
   registers.setSP(returnAddressLocation + 8);
 }
+#endif // _LIBUNWIND_TARGET_X86_64
 
 
 
+#if defined(_LIBUNWIND_TARGET_AARCH64)
 /// CompactUnwinder_arm64 uses a compact unwind info to virtually "step" (aka
 /// unwind) by modifying a Registers_arm64 register set
 template <typename A>
@@ -686,6 +691,7 @@ int CompactUnwinder_arm64<A>::stepWithCompactEncodingFrame(
 
   return UNW_STEP_SUCCESS;
 }
+#endif // _LIBUNWIND_TARGET_AARCH64
 
 
 } // namespace libunwind
diff --git a/src/Registers.hpp b/src/Registers.hpp
index 875ea2063c84..ab8742840004 100644
--- a/src/Registers.hpp
+++ b/src/Registers.hpp
@@ -25,6 +25,7 @@ namespace libunwind {
 struct v128 { uint32_t vec[4]; };
 
 
+#if defined(_LIBUNWIND_TARGET_I386)
 /// Registers_x86 holds the register state of a thread in a 32-bit intel
 /// process.
 class _LIBUNWIND_HIDDEN Registers_x86 {
@@ -86,8 +87,8 @@ private:
 };
 
 inline Registers_x86::Registers_x86(const void *registers) {
-  static_assert(sizeof(Registers_x86) < sizeof(unw_context_t),
-                    "x86 registers do not fit into unw_context_t");
+  static_assert((check_fit<Registers_x86, unw_context_t>::does_fit),
+                "x86 registers do not fit into unw_context_t");
   memcpy(&_registers, registers, sizeof(_registers));
 }
 
@@ -211,8 +212,10 @@ inline v128 Registers_x86::getVectorRegister(int) const {
 inline void Registers_x86::setVectorRegister(int, v128) {
   _LIBUNWIND_ABORT("no x86 vector registers");
 }
+#endif // _LIBUNWIND_TARGET_I386
 
 
+#if defined(_LIBUNWIND_TARGET_X86_64)
 /// Registers_x86_64  holds the register state of a thread in a 64-bit intel
 /// process.
 class _LIBUNWIND_HIDDEN Registers_x86_64 {
@@ -278,8 +281,8 @@ private:
 };
 
 inline Registers_x86_64::Registers_x86_64(const void *registers) {
-  static_assert(sizeof(Registers_x86_64) < sizeof(unw_context_t),
-                    "x86_64 registers do not fit into unw_context_t");
+  static_assert((check_fit<Registers_x86_64, unw_context_t>::does_fit),
+                "x86_64 registers do not fit into unw_context_t");
   memcpy(&_registers, registers, sizeof(_registers));
 }
 
@@ -459,8 +462,10 @@ inline v128 Registers_x86_64::getVectorRegister(int) const {
 inline void Registers_x86_64::setVectorRegister(int, v128) {
   _LIBUNWIND_ABORT("no x86_64 vector registers");
 }
+#endif // _LIBUNWIND_TARGET_X86_64
 
 
+#if defined(_LIBUNWIND_TARGET_PPC)
 /// Registers_ppc holds the register state of a thread in a 32-bit PowerPC
 /// process.
 class _LIBUNWIND_HIDDEN Registers_ppc {
@@ -543,8 +548,8 @@ private:
 };
 
 inline Registers_ppc::Registers_ppc(const void *registers) {
-  static_assert(sizeof(Registers_ppc) < sizeof(unw_context_t),
-                    "ppc registers do not fit into unw_context_t");
+  static_assert((check_fit<Registers_ppc, unw_context_t>::does_fit),
+                "ppc registers do not fit into unw_context_t");
   memcpy(&_registers, static_cast<const uint8_t *>(registers),
          sizeof(_registers));
   static_assert(sizeof(ppc_thread_state_t) == 160,
@@ -1023,8 +1028,10 @@ inline const char *Registers_ppc::getRegisterName(int regNum) {
   }
 
 }
+#endif // _LIBUNWIND_TARGET_PPC
 
 
+#if defined(_LIBUNWIND_TARGET_AARCH64)
 /// Registers_arm64  holds the register state of a thread in a 64-bit arm
 /// process.
 class _LIBUNWIND_HIDDEN Registers_arm64 {
@@ -1071,8 +1078,8 @@ private:
 };
 
 inline Registers_arm64::Registers_arm64(const void *registers) {
-  static_assert(sizeof(Registers_arm64) < sizeof(unw_context_t),
-                    "arm64 registers do not fit into unw_context_t");
+  static_assert((check_fit<Registers_arm64, unw_context_t>::does_fit),
+                "arm64 registers do not fit into unw_context_t");
   memcpy(&_registers, registers, sizeof(_registers));
   static_assert(sizeof(GPRs) == 0x110,
                 "expected VFP registers to be at offset 272");
@@ -1289,7 +1296,9 @@ inline v128 Registers_arm64::getVectorRegister(int) const {
 inline void Registers_arm64::setVectorRegister(int, v128) {
   _LIBUNWIND_ABORT("no arm64 vector register support yet");
 }
+#endif // _LIBUNWIND_TARGET_AARCH64
 
+#if defined(_LIBUNWIND_TARGET_ARM)
 /// Registers_arm holds the register state of a thread in a 32-bit arm
 /// process.
 ///
@@ -1395,8 +1404,8 @@ inline Registers_arm::Registers_arm(const void *registers)
     _saved_vfp_d16_d31(false),
     _saved_iwmmx(false),
     _saved_iwmmx_control(false) {
-  static_assert(sizeof(Registers_arm) < sizeof(unw_context_t),
-                    "arm registers do not fit into unw_context_t");
+  static_assert((check_fit<Registers_arm, unw_context_t>::does_fit),
+                "arm registers do not fit into unw_context_t");
   // See unw_getcontext() note about data.
   memcpy(&_registers, registers, sizeof(_registers));
   memset(&_vfp_d0_d15_pad, 0, sizeof(_vfp_d0_d15_pad));
@@ -1711,6 +1720,10 @@ inline v128 Registers_arm::getVectorRegister(int) const {
 inline void Registers_arm::setVectorRegister(int, v128) {
   _LIBUNWIND_ABORT("ARM vector support not implemented");
 }
+#endif // _LIBUNWIND_TARGET_ARM
+
+
+#if defined(_LIBUNWIND_TARGET_OR1K)
 /// Registers_or1k holds the register state of a thread in an OpenRISC1000
 /// process.
 class _LIBUNWIND_HIDDEN Registers_or1k {
@@ -1745,8 +1758,8 @@ private:
 };
 
 inline Registers_or1k::Registers_or1k(const void *registers) {
-  static_assert(sizeof(Registers_or1k) < sizeof(unw_context_t),
-                    "or1k registers do not fit into unw_context_t");
+  static_assert((check_fit<Registers_or1k, unw_context_t>::does_fit),
+                "or1k registers do not fit into unw_context_t");
   memcpy(&_registers, static_cast<const uint8_t *>(registers),
          sizeof(_registers));
 }
@@ -1893,6 +1906,7 @@ inline const char *Registers_or1k::getRegisterName(int regNum) {
   }
 
 }
+#endif // _LIBUNWIND_TARGET_OR1K
 } // namespace libunwind
 
 #endif // __REGISTERS_HPP__
diff --git a/src/Unwind-EHABI.cpp b/src/Unwind-EHABI.cpp
index bc3df41f35f7..5950c6902e38 100644
--- a/src/Unwind-EHABI.cpp
+++ b/src/Unwind-EHABI.cpp
@@ -438,39 +438,21 @@ extern "C" _Unwind_Reason_Code __aeabi_unwind_cpp_pr2(
 }
 
 static _Unwind_Reason_Code
-unwind_phase1(unw_context_t *uc, _Unwind_Exception *exception_object) {
+unwind_phase1(unw_context_t *uc, unw_cursor_t *cursor, _Unwind_Exception *exception_object) {
   // EHABI #7.3 discusses preserving the VRS in a "temporary VRS" during
   // phase 1 and then restoring it to the "primary VRS" for phase 2. The
   // effect is phase 2 doesn't see any of the VRS manipulations from phase 1.
   // In this implementation, the phases don't share the VRS backing store.
   // Instead, they are passed the original |uc| and they create a new VRS
   // from scratch thus achieving the same effect.
-  unw_cursor_t cursor1;
-  unw_init_local(&cursor1, uc);
+  unw_init_local(cursor, uc);
 
   // Walk each frame looking for a place to stop.
   for (bool handlerNotFound = true; handlerNotFound;) {
 
-#if !_LIBUNWIND_ARM_EHABI
-    // Ask libuwind to get next frame (skip over first which is
-    // _Unwind_RaiseException).
-    int stepResult = unw_step(&cursor1);
-    if (stepResult == 0) {
-      _LIBUNWIND_TRACE_UNWINDING("unwind_phase1(ex_ojb=%p): unw_step() reached "
-                                 "bottom => _URC_END_OF_STACK\n",
-                                 static_cast<void *>(exception_object));
-      return _URC_END_OF_STACK;
-    } else if (stepResult < 0) {
-      _LIBUNWIND_TRACE_UNWINDING("unwind_phase1(ex_ojb=%p): unw_step failed => "
-                                 "_URC_FATAL_PHASE1_ERROR\n",
-                                 static_cast<void *>(exception_object));
-      return _URC_FATAL_PHASE1_ERROR;
-    }
-#endif
-
     // See if frame has code to run (has personality routine).
     unw_proc_info_t frameInfo;
-    if (unw_get_proc_info(&cursor1, &frameInfo) != UNW_ESUCCESS) {
+    if (unw_get_proc_info(cursor, &frameInfo) != UNW_ESUCCESS) {
       _LIBUNWIND_TRACE_UNWINDING("unwind_phase1(ex_ojb=%p): unw_get_proc_info "
                                  "failed => _URC_FATAL_PHASE1_ERROR\n",
                                  static_cast<void *>(exception_object));
@@ -482,12 +464,12 @@ unwind_phase1(unw_context_t *uc, _Unwind_Exception *exception_object) {
       char functionBuf[512];
       const char *functionName = functionBuf;
       unw_word_t offset;
-      if ((unw_get_proc_name(&cursor1, functionBuf, sizeof(functionBuf),
+      if ((unw_get_proc_name(cursor, functionBuf, sizeof(functionBuf),
                              &offset) != UNW_ESUCCESS) ||
           (frameInfo.start_ip + offset > frameInfo.end_ip))
         functionName = ".anonymous.";
       unw_word_t pc;
-      unw_get_reg(&cursor1, UNW_REG_IP, &pc);
+      unw_get_reg(cursor, UNW_REG_IP, &pc);
       _LIBUNWIND_TRACE_UNWINDING(
           "unwind_phase1(ex_ojb=%p): pc=0x%llX, start_ip=0x%llX, func=%s, "
           "lsda=0x%llX, personality=0x%llX\n",
@@ -505,7 +487,7 @@ unwind_phase1(unw_context_t *uc, _Unwind_Exception *exception_object) {
           "unwind_phase1(ex_ojb=%p): calling personality function %p\n",
           static_cast<void *>(exception_object),
           reinterpret_cast<void *>(reinterpret_cast<uintptr_t>(p)));
-      struct _Unwind_Context *context = (struct _Unwind_Context *)(&cursor1);
+      struct _Unwind_Context *context = (struct _Unwind_Context *)(cursor);
       exception_object->pr_cache.fnstart = frameInfo.start_ip;
       exception_object->pr_cache.ehtp =
           (_Unwind_EHT_Header *)frameInfo.unwind_info;
@@ -553,12 +535,11 @@ unwind_phase1(unw_context_t *uc, _Unwind_Exception *exception_object) {
   return _URC_NO_REASON;
 }
 
-static _Unwind_Reason_Code unwind_phase2(unw_context_t *uc,
+static _Unwind_Reason_Code unwind_phase2(unw_context_t *uc, unw_cursor_t *cursor,
                                          _Unwind_Exception *exception_object,
                                          bool resume) {
   // See comment at the start of unwind_phase1 regarding VRS integrity.
-  unw_cursor_t cursor2;
-  unw_init_local(&cursor2, uc);
+  unw_init_local(cursor, uc);
 
   _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_ojb=%p)\n",
                              static_cast<void *>(exception_object));
@@ -580,31 +561,16 @@ static _Unwind_Reason_Code unwind_phase2(unw_context_t *uc,
       // for. After this, continue unwinding as if normal.
       //
       // See #7.4.6 for details.
-      unw_set_reg(&cursor2, UNW_REG_IP,
+      unw_set_reg(cursor, UNW_REG_IP,
                   exception_object->unwinder_cache.reserved2);
       resume = false;
     }
 
-#if !_LIBUNWIND_ARM_EHABI
-    int stepResult = unw_step(&cursor2);
-    if (stepResult == 0) {
-      _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_ojb=%p): unw_step() reached "
-                                 "bottom => _URC_END_OF_STACK\n",
-                                 static_cast<void *>(exception_object));
-      return _URC_END_OF_STACK;
-    } else if (stepResult < 0) {
-      _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_ojb=%p): unw_step failed => "
-                                 "_URC_FATAL_PHASE1_ERROR\n",
-                                 static_cast<void *>(exception_object));
-      return _URC_FATAL_PHASE2_ERROR;
-    }
-#endif
-
     // Get info about this frame.
     unw_word_t sp;
     unw_proc_info_t frameInfo;
-    unw_get_reg(&cursor2, UNW_REG_SP, &sp);
-    if (unw_get_proc_info(&cursor2, &frameInfo) != UNW_ESUCCESS) {
+    unw_get_reg(cursor, UNW_REG_SP, &sp);
+    if (unw_get_proc_info(cursor, &frameInfo) != UNW_ESUCCESS) {
       _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_ojb=%p): unw_get_proc_info "
                                  "failed => _URC_FATAL_PHASE1_ERROR\n",
                                  static_cast<void *>(exception_object));
@@ -616,7 +582,7 @@ static _Unwind_Reason_Code unwind_phase2(unw_context_t *uc,
       char functionBuf[512];
       const char *functionName = functionBuf;
       unw_word_t offset;
-      if ((unw_get_proc_name(&cursor2, functionBuf, sizeof(functionBuf),
+      if ((unw_get_proc_name(cursor, functionBuf, sizeof(functionBuf),
                              &offset) != UNW_ESUCCESS) ||
           (frameInfo.start_ip + offset > frameInfo.end_ip))
         functionName = ".anonymous.";
@@ -632,7 +598,7 @@ static _Unwind_Reason_Code unwind_phase2(unw_context_t *uc,
     if (frameInfo.handler != 0) {
       __personality_routine p =
           (__personality_routine)(long)(frameInfo.handler);
-      struct _Unwind_Context *context = (struct _Unwind_Context *)(&cursor2);
+      struct _Unwind_Context *context = (struct _Unwind_Context *)(cursor);
       // EHABI #7.2
       exception_object->pr_cache.fnstart = frameInfo.start_ip;
       exception_object->pr_cache.ehtp =
@@ -661,8 +627,8 @@ static _Unwind_Reason_Code unwind_phase2(unw_context_t *uc,
         // We may get control back if landing pad calls _Unwind_Resume().
         if (_LIBUNWIND_TRACING_UNWINDING) {
           unw_word_t pc;
-          unw_get_reg(&cursor2, UNW_REG_IP, &pc);
-          unw_get_reg(&cursor2, UNW_REG_SP, &sp);
+          unw_get_reg(cursor, UNW_REG_IP, &pc);
+          unw_get_reg(cursor, UNW_REG_SP, &sp);
           _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_ojb=%p): re-entering "
                                      "user code with ip=0x%llX, sp=0x%llX\n",
                                      static_cast<void *>(exception_object),
@@ -673,10 +639,10 @@ static _Unwind_Reason_Code unwind_phase2(unw_context_t *uc,
           // EHABI #7.4.1 says we need to preserve pc for when _Unwind_Resume
           // is called back, to find this same frame.
           unw_word_t pc;
-          unw_get_reg(&cursor2, UNW_REG_IP, &pc);
+          unw_get_reg(cursor, UNW_REG_IP, &pc);
           exception_object->unwinder_cache.reserved2 = (uint32_t)pc;
         }
-        unw_resume(&cursor2);
+        unw_resume(cursor);
         // unw_resume() only returns if there was an error.
         return _URC_FATAL_PHASE2_ERROR;
 
@@ -705,6 +671,7 @@ _Unwind_RaiseException(_Unwind_Exception *exception_object) {
   _LIBUNWIND_TRACE_API("_Unwind_RaiseException(ex_obj=%p)\n",
                        static_cast<void *>(exception_object));
   unw_context_t uc;
+  unw_cursor_t cursor;
   unw_getcontext(&uc);
 
   // This field for is for compatibility with GCC to say this isn't a forced
@@ -712,12 +679,12 @@ _Unwind_RaiseException(_Unwind_Exception *exception_object) {
   exception_object->unwinder_cache.reserved1 = 0;
 
   // phase 1: the search phase
-  _Unwind_Reason_Code phase1 = unwind_phase1(&uc, exception_object);
+  _Unwind_Reason_Code phase1 = unwind_phase1(&uc, &cursor, exception_object);
   if (phase1 != _URC_NO_REASON)
     return phase1;
 
   // phase 2: the clean up phase
-  return unwind_phase2(&uc, exception_object, false);
+  return unwind_phase2(&uc, &cursor, exception_object, false);
 }
 
 _LIBUNWIND_EXPORT void _Unwind_Complete(_Unwind_Exception* exception_object) {
@@ -742,12 +709,13 @@ _Unwind_Resume(_Unwind_Exception *exception_object) {
   _LIBUNWIND_TRACE_API("_Unwind_Resume(ex_obj=%p)\n",
                        static_cast<void *>(exception_object));
   unw_context_t uc;
+  unw_cursor_t cursor;
   unw_getcontext(&uc);
 
   // _Unwind_RaiseException on EHABI will always set the reserved1 field to 0,
   // which is in the same position as private_1 below.
   // TODO(ajwong): Who wronte the above? Why is it true?
-  unwind_phase2(&uc, exception_object, true);
+  unwind_phase2(&uc, &cursor, exception_object, true);
 
   // Clients assume _Unwind_Resume() does not return, so all we can do is abort.
   _LIBUNWIND_ABORT("_Unwind_Resume() can't return");
diff --git a/src/UnwindCursor.hpp b/src/UnwindCursor.hpp
index 90683164ff24..18a780919b11 100644
--- a/src/UnwindCursor.hpp
+++ b/src/UnwindCursor.hpp
@@ -481,30 +481,39 @@ private:
     return stepWithCompactEncoding(dummy);
   }
 
+#if defined(_LIBUNWIND_TARGET_X86_64)
   int stepWithCompactEncoding(Registers_x86_64 &) {
     return CompactUnwinder_x86_64<A>::stepWithCompactEncoding(
         _info.format, _info.start_ip, _addressSpace, _registers);
   }
+#endif
 
+#if defined(_LIBUNWIND_TARGET_I386)
   int stepWithCompactEncoding(Registers_x86 &) {
     return CompactUnwinder_x86<A>::stepWithCompactEncoding(
         _info.format, (uint32_t)_info.start_ip, _addressSpace, _registers);
   }
+#endif
 
+#if defined(_LIBUNWIND_TARGET_PPC)
   int stepWithCompactEncoding(Registers_ppc &) {
     return UNW_EINVAL;
   }
+#endif
 
+#if defined(_LIBUNWIND_TARGET_AARCH64)
   int stepWithCompactEncoding(Registers_arm64 &) {
     return CompactUnwinder_arm64<A>::stepWithCompactEncoding(
         _info.format, _info.start_ip, _addressSpace, _registers);
   }
+#endif
 
   bool compactSaysUseDwarf(uint32_t *offset=NULL) const {
     R dummy;
     return compactSaysUseDwarf(dummy, offset);
   }
 
+#if defined(_LIBUNWIND_TARGET_X86_64)
   bool compactSaysUseDwarf(Registers_x86_64 &, uint32_t *offset) const {
     if ((_info.format & UNWIND_X86_64_MODE_MASK) == UNWIND_X86_64_MODE_DWARF) {
       if (offset)
@@ -513,7 +522,9 @@ private:
     }
     return false;
   }
+#endif
 
+#if defined(_LIBUNWIND_TARGET_I386)
   bool compactSaysUseDwarf(Registers_x86 &, uint32_t *offset) const {
     if ((_info.format & UNWIND_X86_MODE_MASK) == UNWIND_X86_MODE_DWARF) {
       if (offset)
@@ -522,11 +533,15 @@ private:
     }
     return false;
   }
+#endif
 
+#if defined(_LIBUNWIND_TARGET_PPC)
   bool compactSaysUseDwarf(Registers_ppc &, uint32_t *) const {
     return true;
   }
+#endif
 
+#if defined(_LIBUNWIND_TARGET_AARCH64)
   bool compactSaysUseDwarf(Registers_arm64 &, uint32_t *offset) const {
     if ((_info.format & UNWIND_ARM64_MODE_MASK) == UNWIND_ARM64_MODE_DWARF) {
       if (offset)
@@ -535,6 +550,7 @@ private:
     }
     return false;
   }
+#endif
 #endif // _LIBUNWIND_SUPPORT_COMPACT_UNWIND
 
 #if _LIBUNWIND_SUPPORT_DWARF_UNWIND
@@ -543,25 +559,35 @@ private:
     return dwarfEncoding(dummy);
   }
 
+#if defined(_LIBUNWIND_TARGET_X86_64)
   compact_unwind_encoding_t dwarfEncoding(Registers_x86_64 &) const {
     return UNWIND_X86_64_MODE_DWARF;
   }
+#endif
 
+#if defined(_LIBUNWIND_TARGET_I386)
   compact_unwind_encoding_t dwarfEncoding(Registers_x86 &) const {
     return UNWIND_X86_MODE_DWARF;
   }
+#endif
 
+#if defined(_LIBUNWIND_TARGET_PPC)
   compact_unwind_encoding_t dwarfEncoding(Registers_ppc &) const {
     return 0;
   }
+#endif
 
+#if defined(_LIBUNWIND_TARGET_AARCH64)
   compact_unwind_encoding_t dwarfEncoding(Registers_arm64 &) const {
     return UNWIND_ARM64_MODE_DWARF;
   }
+#endif
 
+#if defined (_LIBUNWIND_TARGET_OR1K)
   compact_unwind_encoding_t dwarfEncoding(Registers_or1k &) const {
     return 0;
   }
+#endif
 #endif // _LIBUNWIND_SUPPORT_DWARF_UNWIND
 
 
@@ -577,7 +603,7 @@ template <typename A, typename R>
 UnwindCursor<A, R>::UnwindCursor(unw_context_t *context, A &as)
     : _addressSpace(as), _registers(context), _unwindInfoMissing(false),
       _isSignalFrame(false) {
-  static_assert(sizeof(UnwindCursor<A, R>) < sizeof(unw_cursor_t),
+  static_assert((check_fit<UnwindCursor<A, R>, unw_cursor_t>::does_fit),
                 "UnwindCursor<> does not fit in unw_cursor_t");
   memset(&_info, 0, sizeof(_info));
 }
diff --git a/src/UnwindLevel1.c b/src/UnwindLevel1.c
index ce6eb286bab3..7294f255407e 100644
--- a/src/UnwindLevel1.c
+++ b/src/UnwindLevel1.c
@@ -33,16 +33,15 @@
 #if !_LIBUNWIND_ARM_EHABI
 
 static _Unwind_Reason_Code
-unwind_phase1(unw_context_t *uc, _Unwind_Exception *exception_object) {
-  unw_cursor_t cursor1;
-  unw_init_local(&cursor1, uc);
+unwind_phase1(unw_context_t *uc, unw_cursor_t *cursor, _Unwind_Exception *exception_object) {
+  unw_init_local(cursor, uc);
 
   // Walk each frame looking for a place to stop.
   bool handlerNotFound = true;
   while (handlerNotFound) {
     // Ask libuwind to get next frame (skip over first which is
     // _Unwind_RaiseException).
-    int stepResult = unw_step(&cursor1);
+    int stepResult = unw_step(cursor);
     if (stepResult == 0) {
       _LIBUNWIND_TRACE_UNWINDING("unwind_phase1(ex_ojb=%p): unw_step() reached "
                                  "bottom => _URC_END_OF_STACK\n",
@@ -58,7 +57,7 @@ unwind_phase1(unw_context_t *uc, _Unwind_Exception *exception_object) {
     // See if frame has code to run (has personality routine).
     unw_proc_info_t frameInfo;
     unw_word_t sp;
-    if (unw_get_proc_info(&cursor1, &frameInfo) != UNW_ESUCCESS) {
+    if (unw_get_proc_info(cursor, &frameInfo) != UNW_ESUCCESS) {
       _LIBUNWIND_TRACE_UNWINDING("unwind_phase1(ex_ojb=%p): unw_get_proc_info "
                                  "failed => _URC_FATAL_PHASE1_ERROR\n",
                                  (void *)exception_object);
@@ -70,12 +69,12 @@ unwind_phase1(unw_context_t *uc, _Unwind_Exception *exception_object) {
       char functionBuf[512];
       const char *functionName = functionBuf;
       unw_word_t offset;
-      if ((unw_get_proc_name(&cursor1, functionBuf, sizeof(functionBuf),
+      if ((unw_get_proc_name(cursor, functionBuf, sizeof(functionBuf),
                              &offset) != UNW_ESUCCESS) ||
           (frameInfo.start_ip + offset > frameInfo.end_ip))
         functionName = ".anonymous.";
       unw_word_t pc;
-      unw_get_reg(&cursor1, UNW_REG_IP, &pc);
+      unw_get_reg(cursor, UNW_REG_IP, &pc);
       _LIBUNWIND_TRACE_UNWINDING(
           "unwind_phase1(ex_ojb=%p): pc=0x%" PRIx64 ", start_ip=0x%" PRIx64
           ", func=%s, lsda=0x%" PRIx64 ", personality=0x%" PRIx64 "\n",
@@ -93,13 +92,13 @@ unwind_phase1(unw_context_t *uc, _Unwind_Exception *exception_object) {
           (void *)exception_object, (void *)(uintptr_t)p);
       _Unwind_Reason_Code personalityResult =
           (*p)(1, _UA_SEARCH_PHASE, exception_object->exception_class,
-               exception_object, (struct _Unwind_Context *)(&cursor1));
+               exception_object, (struct _Unwind_Context *)(cursor));
       switch (personalityResult) {
       case _URC_HANDLER_FOUND:
         // found a catch clause or locals that need destructing in this frame
         // stop search and remember stack pointer at the frame
         handlerNotFound = false;
-        unw_get_reg(&cursor1, UNW_REG_SP, &sp);
+        unw_get_reg(cursor, UNW_REG_SP, &sp);
         exception_object->private_2 = (uintptr_t)sp;
         _LIBUNWIND_TRACE_UNWINDING(
             "unwind_phase1(ex_ojb=%p): _URC_HANDLER_FOUND \n",
@@ -127,9 +126,8 @@ unwind_phase1(unw_context_t *uc, _Unwind_Exception *exception_object) {
 
 
 static _Unwind_Reason_Code
-unwind_phase2(unw_context_t *uc, _Unwind_Exception *exception_object) {
-  unw_cursor_t cursor2;
-  unw_init_local(&cursor2, uc);
+unwind_phase2(unw_context_t *uc, unw_cursor_t *cursor, _Unwind_Exception *exception_object) {
+  unw_init_local(cursor, uc);
 
   _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_ojb=%p)\n",
                              (void *)exception_object);
@@ -139,7 +137,7 @@ unwind_phase2(unw_context_t *uc, _Unwind_Exception *exception_object) {
 
     // Ask libuwind to get next frame (skip over first which is
     // _Unwind_RaiseException).
-    int stepResult = unw_step(&cursor2);
+    int stepResult = unw_step(cursor);
     if (stepResult == 0) {
       _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_ojb=%p): unw_step() reached "
                                  "bottom => _URC_END_OF_STACK\n",
@@ -155,8 +153,8 @@ unwind_phase2(unw_context_t *uc, _Unwind_Exception *exception_object) {
     // Get info about this frame.
     unw_word_t sp;
     unw_proc_info_t frameInfo;
-    unw_get_reg(&cursor2, UNW_REG_SP, &sp);
-    if (unw_get_proc_info(&cursor2, &frameInfo) != UNW_ESUCCESS) {
+    unw_get_reg(cursor, UNW_REG_SP, &sp);
+    if (unw_get_proc_info(cursor, &frameInfo) != UNW_ESUCCESS) {
       _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_ojb=%p): unw_get_proc_info "
                                  "failed => _URC_FATAL_PHASE1_ERROR\n",
                                  (void *)exception_object);
@@ -168,7 +166,7 @@ unwind_phase2(unw_context_t *uc, _Unwind_Exception *exception_object) {
       char functionBuf[512];
       const char *functionName = functionBuf;
       unw_word_t offset;
-      if ((unw_get_proc_name(&cursor2, functionBuf, sizeof(functionBuf),
+      if ((unw_get_proc_name(cursor, functionBuf, sizeof(functionBuf),
                              &offset) != UNW_ESUCCESS) ||
           (frameInfo.start_ip + offset > frameInfo.end_ip))
         functionName = ".anonymous.";
@@ -191,7 +189,7 @@ unwind_phase2(unw_context_t *uc, _Unwind_Exception *exception_object) {
       }
        _Unwind_Reason_Code personalityResult =
           (*p)(1, action, exception_object->exception_class, exception_object,
-               (struct _Unwind_Context *)(&cursor2));
+               (struct _Unwind_Context *)(cursor));
       switch (personalityResult) {
       case _URC_CONTINUE_UNWIND:
         // Continue unwinding
@@ -212,14 +210,14 @@ unwind_phase2(unw_context_t *uc, _Unwind_Exception *exception_object) {
         // We may get control back if landing pad calls _Unwind_Resume().
         if (_LIBUNWIND_TRACING_UNWINDING) {
           unw_word_t pc;
-          unw_get_reg(&cursor2, UNW_REG_IP, &pc);
-          unw_get_reg(&cursor2, UNW_REG_SP, &sp);
+          unw_get_reg(cursor, UNW_REG_IP, &pc);
+          unw_get_reg(cursor, UNW_REG_SP, &sp);
           _LIBUNWIND_TRACE_UNWINDING("unwind_phase2(ex_ojb=%p): re-entering "
                                      "user code with ip=0x%" PRIx64
                                      ", sp=0x%" PRIx64 "\n",
                                      (void *)exception_object, pc, sp);
         }
-        unw_resume(&cursor2);
+        unw_resume(cursor);
         // unw_resume() only returns if there was an error.
         return _URC_FATAL_PHASE2_ERROR;
       default:
@@ -237,18 +235,17 @@ unwind_phase2(unw_context_t *uc, _Unwind_Exception *exception_object) {
 }
 
 static _Unwind_Reason_Code
-unwind_phase2_forced(unw_context_t *uc,
+unwind_phase2_forced(unw_context_t *uc, unw_cursor_t *cursor,
                      _Unwind_Exception *exception_object,
                      _Unwind_Stop_Fn stop, void *stop_parameter) {
-  unw_cursor_t cursor2;
-  unw_init_local(&cursor2, uc);
+  unw_init_local(cursor, uc);
 
   // Walk each frame until we reach where search phase said to stop
-  while (unw_step(&cursor2) > 0) {
+  while (unw_step(cursor) > 0) {
 
     // Update info about this frame.
     unw_proc_info_t frameInfo;
-    if (unw_get_proc_info(&cursor2, &frameInfo) != UNW_ESUCCESS) {
+    if (unw_get_proc_info(cursor, &frameInfo) != UNW_ESUCCESS) {
       _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): unw_step "
                                  "failed => _URC_END_OF_STACK\n",
                                  (void *)exception_object);
@@ -260,7 +257,7 @@ unwind_phase2_forced(unw_context_t *uc,
       char functionBuf[512];
       const char *functionName = functionBuf;
       unw_word_t offset;
-      if ((unw_get_proc_name(&cursor2, functionBuf, sizeof(functionBuf),
+      if ((unw_get_proc_name(cursor, functionBuf, sizeof(functionBuf),
                              &offset) != UNW_ESUCCESS) ||
           (frameInfo.start_ip + offset > frameInfo.end_ip))
         functionName = ".anonymous.";
@@ -276,7 +273,7 @@ unwind_phase2_forced(unw_context_t *uc,
         (_Unwind_Action)(_UA_FORCE_UNWIND | _UA_CLEANUP_PHASE);
     _Unwind_Reason_Code stopResult =
         (*stop)(1, action, exception_object->exception_class, exception_object,
-                (struct _Unwind_Context *)(&cursor2), stop_parameter);
+                (struct _Unwind_Context *)(cursor), stop_parameter);
     _LIBUNWIND_TRACE_UNWINDING(
         "unwind_phase2_forced(ex_ojb=%p): stop function returned %d\n",
         (void *)exception_object, stopResult);
@@ -296,7 +293,7 @@ unwind_phase2_forced(unw_context_t *uc,
           (void *)exception_object, (void *)(uintptr_t)p);
       _Unwind_Reason_Code personalityResult =
           (*p)(1, action, exception_object->exception_class, exception_object,
-               (struct _Unwind_Context *)(&cursor2));
+               (struct _Unwind_Context *)(cursor));
       switch (personalityResult) {
       case _URC_CONTINUE_UNWIND:
         _LIBUNWIND_TRACE_UNWINDING("unwind_phase2_forced(ex_ojb=%p): "
@@ -311,7 +308,7 @@ unwind_phase2_forced(unw_context_t *uc,
                                    "_URC_INSTALL_CONTEXT\n",
                                    (void *)exception_object);
         // We may get control back if landing pad calls _Unwind_Resume().
-        unw_resume(&cursor2);
+        unw_resume(cursor);
         break;
       default:
         // Personality routine returned an unknown result code.
@@ -332,7 +329,7 @@ unwind_phase2_forced(unw_context_t *uc,
   _Unwind_Action lastAction =
       (_Unwind_Action)(_UA_FORCE_UNWIND | _UA_CLEANUP_PHASE | _UA_END_OF_STACK);
   (*stop)(1, lastAction, exception_object->exception_class, exception_object,
-          (struct _Unwind_Context *)(&cursor2), stop_parameter);
+          (struct _Unwind_Context *)(cursor), stop_parameter);
 
   // Clean up phase did not resume at the frame that the search phase said it
   // would.
@@ -346,6 +343,7 @@ _Unwind_RaiseException(_Unwind_Exception *exception_object) {
   _LIBUNWIND_TRACE_API("_Unwind_RaiseException(ex_obj=%p)\n",
                        (void *)exception_object);
   unw_context_t uc;
+  unw_cursor_t cursor;
   unw_getcontext(&uc);
 
   // Mark that this is a non-forced unwind, so _Unwind_Resume()
@@ -354,12 +352,12 @@ _Unwind_RaiseException(_Unwind_Exception *exception_object) {
   exception_object->private_2 = 0;
 
   // phase 1: the search phase
-  _Unwind_Reason_Code phase1 = unwind_phase1(&uc, exception_object);
+  _Unwind_Reason_Code phase1 = unwind_phase1(&uc, &cursor, exception_object);
   if (phase1 != _URC_NO_REASON)
     return phase1;
 
   // phase 2: the clean up phase
-  return unwind_phase2(&uc, exception_object);
+  return unwind_phase2(&uc, &cursor, exception_object);
 }
 
 
@@ -379,14 +377,15 @@ _LIBUNWIND_EXPORT void
 _Unwind_Resume(_Unwind_Exception *exception_object) {
   _LIBUNWIND_TRACE_API("_Unwind_Resume(ex_obj=%p)\n", (void *)exception_object);
   unw_context_t uc;
+  unw_cursor_t cursor;
   unw_getcontext(&uc);
 
   if (exception_object->private_1 != 0)
-    unwind_phase2_forced(&uc, exception_object,
+    unwind_phase2_forced(&uc, &cursor, exception_object,
                          (_Unwind_Stop_Fn) exception_object->private_1,
                          (void *)exception_object->private_2);
   else
-    unwind_phase2(&uc, exception_object);
+    unwind_phase2(&uc, &cursor, exception_object);
 
   // Clients assume _Unwind_Resume() does not return, so all we can do is abort.
   _LIBUNWIND_ABORT("_Unwind_Resume() can't return");
@@ -403,6 +402,7 @@ _Unwind_ForcedUnwind(_Unwind_Exception *exception_object,
   _LIBUNWIND_TRACE_API("_Unwind_ForcedUnwind(ex_obj=%p, stop=%p)\n",
                        (void *)exception_object, (void *)(uintptr_t)stop);
   unw_context_t uc;
+  unw_cursor_t cursor;
   unw_getcontext(&uc);
 
   // Mark that this is a forced unwind, so _Unwind_Resume() can do
@@ -411,7 +411,7 @@ _Unwind_ForcedUnwind(_Unwind_Exception *exception_object,
   exception_object->private_2 = (uintptr_t) stop_parameter;
 
   // do it
-  return unwind_phase2_forced(&uc, exception_object, stop, stop_parameter);
+  return unwind_phase2_forced(&uc, &cursor, exception_object, stop, stop_parameter);
 }
 
 
diff --git a/src/UnwindRegistersRestore.S b/src/UnwindRegistersRestore.S
index 3a4ea62f6e29..d5ecc6ed2acd 100644
--- a/src/UnwindRegistersRestore.S
+++ b/src/UnwindRegistersRestore.S
@@ -282,8 +282,8 @@ DEFINE_LIBUNWIND_PRIVATE_FUNCTION(_ZN9libunwind15Registers_arm646jumptoEv)
   ldp    x22,x23, [x0, #0x0B0]
   ldp    x24,x25, [x0, #0x0C0]
   ldp    x26,x27, [x0, #0x0D0]
-  ldp    x28,fp,  [x0, #0x0E0]
-  ldr    lr,      [x0, #0x100]  // restore pc into lr
+  ldp    x28,x29, [x0, #0x0E0]
+  ldr    x30,     [x0, #0x100]  // restore pc into lr
   ldr    x1,      [x0, #0x0F8]
   mov    sp,x1                  // restore sp
 
@@ -306,7 +306,7 @@ DEFINE_LIBUNWIND_PRIVATE_FUNCTION(_ZN9libunwind15Registers_arm646jumptoEv)
   ldr    d31,     [x0, #0x208]
 
   ldp    x0, x1,  [x0, #0x000]  // restore x0,x1
-  ret    lr                     // jump to pc
+  ret    x30                    // jump to pc
 
 #elif defined(__arm__) && !defined(__APPLE__)
 
diff --git a/src/UnwindRegistersSave.S b/src/UnwindRegistersSave.S
index f84b7114f777..82becffa0e45 100644
--- a/src/UnwindRegistersSave.S
+++ b/src/UnwindRegistersSave.S
@@ -263,11 +263,11 @@ DEFINE_LIBUNWIND_FUNCTION(unw_getcontext)
   stp    x22,x23, [x0, #0x0B0]
   stp    x24,x25, [x0, #0x0C0]
   stp    x26,x27, [x0, #0x0D0]
-  stp    x28,fp,  [x0, #0x0E0]
-  str    lr,      [x0, #0x0F0]
+  stp    x28,x29, [x0, #0x0E0]
+  str    x30,     [x0, #0x0F0]
   mov    x1,sp
   str    x1,      [x0, #0x0F8]
-  str    lr,      [x0, #0x100]    // store return address as pc
+  str    x30,     [x0, #0x100]    // store return address as pc
   // skip cpsr
   stp    d0, d1,  [x0, #0x110]
   stp    d2, d3,  [x0, #0x120]
diff --git a/src/config.h b/src/config.h
index ecc0a6b4465d..a50222f7c90d 100644
--- a/src/config.h
+++ b/src/config.h
@@ -16,6 +16,7 @@
 
 #include <assert.h>
 #include <stdio.h>
+#include <stdlib.h>
 
 // Define static_assert() unless already defined by compiler.
 #ifndef __has_feature
@@ -29,28 +30,6 @@
 
 // Platform specific configuration defines.
 #ifdef __APPLE__
-  #include <Availability.h>
-  #ifdef __cplusplus
-    extern "C" {
-  #endif
-    void __assert_rtn(const char *, const char *, int, const char *)
-                                                      __attribute__((noreturn));
-  #ifdef __cplusplus
-    }
-  #endif
-
-  #define _LIBUNWIND_BUILD_ZERO_COST_APIS (defined(__i386__) || \
-                                           defined(__x86_64__) || \
-                                           defined(__arm64__) || \
-                                           defined(__mips__))
-  #define _LIBUNWIND_BUILD_SJLJ_APIS      defined(__arm__)
-  #define _LIBUNWIND_SUPPORT_FRAME_APIS   (defined(__i386__) || \
-                                           defined(__x86_64__))
-  #define _LIBUNWIND_EXPORT               __attribute__((visibility("default")))
-  #define _LIBUNWIND_HIDDEN               __attribute__((visibility("hidden")))
-  #define _LIBUNWIND_LOG(msg, ...) fprintf(stderr, "libuwind: " msg, __VA_ARGS__)
-  #define _LIBUNWIND_ABORT(msg) __assert_rtn(__func__, __FILE__, __LINE__, msg)
-
   #if defined(FOR_DYLD)
     #define _LIBUNWIND_SUPPORT_COMPACT_UNWIND 1
     #define _LIBUNWIND_SUPPORT_DWARF_UNWIND   0
@@ -60,35 +39,51 @@
     #define _LIBUNWIND_SUPPORT_DWARF_UNWIND   1
     #define _LIBUNWIND_SUPPORT_DWARF_INDEX    0
   #endif
-
 #else
-  #include <stdlib.h>
+  #if defined(__ARM_DWARF_EH__) || !defined(__arm__)
+    #define _LIBUNWIND_SUPPORT_COMPACT_UNWIND 0
+    #define _LIBUNWIND_SUPPORT_DWARF_UNWIND 1
+    #define _LIBUNWIND_SUPPORT_DWARF_INDEX 1
+  #else
+    #define _LIBUNWIND_SUPPORT_COMPACT_UNWIND 0
+    #define _LIBUNWIND_SUPPORT_DWARF_UNWIND 0
+    #define _LIBUNWIND_SUPPORT_DWARF_INDEX 0
+  #endif
+#endif
+
+// FIXME: these macros are not correct for COFF targets
+#define _LIBUNWIND_EXPORT __attribute__((visibility("default")))
+#define _LIBUNWIND_HIDDEN __attribute__((visibility("hidden")))
 
-  static inline void assert_rtn(const char* func, const char* file, int line, const char* msg)  __attribute__ ((noreturn));
-  static inline void assert_rtn(const char* func, const char* file, int line, const char* msg) {
-    fprintf(stderr, "libunwind: %s %s:%d - %s\n",  func, file, line, msg);
-    assert(false);
-    abort();
-  }
+#if (defined(__APPLE__) && defined(__arm__)) || defined(__USING_SJLJ_EXCEPTIONS__)
+#define _LIBUNWIND_BUILD_SJLJ_APIS 1
+#else
+#define _LIBUNWIND_BUILD_SJLJ_APIS 0
+#endif
 
-  #define _LIBUNWIND_BUILD_ZERO_COST_APIS (defined(__i386__) || \
-                                           defined(__x86_64__) || \
-                                           defined(__arm__) || \
-                                           defined(__aarch64__))
-  #define _LIBUNWIND_BUILD_SJLJ_APIS      0
-  #define _LIBUNWIND_SUPPORT_FRAME_APIS   (defined(__i386__) || \
-                                           defined(__x86_64__))
-  #define _LIBUNWIND_EXPORT               __attribute__((visibility("default")))
-  #define _LIBUNWIND_HIDDEN               __attribute__((visibility("hidden")))
-  #define _LIBUNWIND_LOG(msg, ...) fprintf(stderr, "libuwind: " msg, __VA_ARGS__)
-  #define _LIBUNWIND_ABORT(msg) assert_rtn(__func__, __FILE__, __LINE__, msg)
+#if defined(__i386__) || defined(__x86_64__)
+#define _LIBUNWIND_SUPPORT_FRAME_APIS 1
+#else
+#define _LIBUNWIND_SUPPORT_FRAME_APIS 0
+#endif
 
-  #define _LIBUNWIND_SUPPORT_COMPACT_UNWIND 0
-  #define _LIBUNWIND_SUPPORT_DWARF_UNWIND !defined(__arm__) || \
-                                          defined(__ARM_DWARF_EH__)
-  #define _LIBUNWIND_SUPPORT_DWARF_INDEX _LIBUNWIND_SUPPORT_DWARF_UNWIND
+#if defined(__i386__) || defined(__x86_64__) ||                                \
+    (!defined(__APPLE__) && defined(__arm__)) ||                               \
+    (defined(__arm64__) || defined(__aarch64__)) ||                            \
+    (defined(__APPLE__) && defined(__mips__))
+#define _LIBUNWIND_BUILD_ZERO_COST_APIS 1
+#else
+#define _LIBUNWIND_BUILD_ZERO_COST_APIS 0
 #endif
 
+#define _LIBUNWIND_ABORT(msg)                                                  \
+  do {                                                                         \
+    fprintf(stderr, "libunwind: %s %s:%d - %s\n", __func__, __FILE__,          \
+            __LINE__, msg);                                                    \
+    fflush(stderr);                                                            \
+    abort();                                                                   \
+  } while (0)
+#define _LIBUNWIND_LOG(msg, ...) fprintf(stderr, "libuwind: " msg, __VA_ARGS__)
 
 // Macros that define away in non-Debug builds
 #ifdef NDEBUG
@@ -124,5 +119,25 @@
   #define _LIBUNWIND_TRACING_UNWINDING logUnwinding()
 #endif
 
+#ifdef __cplusplus
+// Used to fit UnwindCursor and Registers_xxx types against unw_context_t /
+// unw_cursor_t sized memory blocks.
+#if defined(_LIBUNWIND_IS_NATIVE_ONLY)
+# define COMP_OP ==
+#else
+# define COMP_OP <
+#endif
+template <typename _Type, typename _Mem>
+struct check_fit {
+  template <typename T>
+  struct blk_count {
+    static const size_t count =
+      (sizeof(T) + sizeof(uint64_t) - 1) / sizeof(uint64_t);
+  };
+  static const bool does_fit =
+    (blk_count<_Type>::count COMP_OP blk_count<_Mem>::count);
+};
+#undef COMP_OP
+#endif // __cplusplus
 
 #endif // LIBUNWIND_CONFIG_H
diff --git a/src/libunwind.cpp b/src/libunwind.cpp
index f9f32f00ece2..95f2dc020dc4 100644
--- a/src/libunwind.cpp
+++ b/src/libunwind.cpp
@@ -45,30 +45,27 @@ _LIBUNWIND_EXPORT int unw_init_local(unw_cursor_t *cursor,
   _LIBUNWIND_TRACE_API("unw_init_local(cursor=%p, context=%p)\n",
                        static_cast<void *>(cursor),
                        static_cast<void *>(context));
-  // Use "placement new" to allocate UnwindCursor in the cursor buffer.
 #if defined(__i386__)
-  new ((void *)cursor) UnwindCursor<LocalAddressSpace, Registers_x86>(
-                                 context, LocalAddressSpace::sThisAddressSpace);
+# define REGISTER_KIND Registers_x86
 #elif defined(__x86_64__)
-  new ((void *)cursor) UnwindCursor<LocalAddressSpace, Registers_x86_64>(
-                                 context, LocalAddressSpace::sThisAddressSpace);
+# define REGISTER_KIND Registers_x86_64
 #elif defined(__ppc__)
-  new ((void *)cursor) UnwindCursor<LocalAddressSpace, Registers_ppc>(
-                                 context, LocalAddressSpace::sThisAddressSpace);
-#elif defined(__arm64__) || defined(__aarch64__)
-  new ((void *)cursor) UnwindCursor<LocalAddressSpace, Registers_arm64>(
-                                 context, LocalAddressSpace::sThisAddressSpace);
+# define REGISTER_KIND Registers_ppc
+#elif defined(__aarch64__)
+# define REGISTER_KIND Registers_arm64
 #elif _LIBUNWIND_ARM_EHABI
-  new ((void *)cursor) UnwindCursor<LocalAddressSpace, Registers_arm>(
-                                 context, LocalAddressSpace::sThisAddressSpace);
+# define REGISTER_KIND Registers_arm
 #elif defined(__or1k__)
-  new ((void *)cursor) UnwindCursor<LocalAddressSpace, Registers_or1k>(
-                                 context, LocalAddressSpace::sThisAddressSpace);
+# define REGISTER_KIND Registers_or1k
 #elif defined(__mips__)
-#warning The MIPS architecture is not supported.
+# warning The MIPS architecture is not supported.
 #else
-#error Architecture not supported
+# error Architecture not supported
 #endif
+  // Use "placement new" to allocate UnwindCursor in the cursor buffer.
+  new ((void *)cursor) UnwindCursor<LocalAddressSpace, REGISTER_KIND>(
+                                 context, LocalAddressSpace::sThisAddressSpace);
+#undef REGISTER_KIND
   AbstractUnwindCursor *co = (AbstractUnwindCursor *)cursor;
   co->setInfoBasedOnIPRegister();