diff --git a/libunwind/src/config.h b/libunwind/src/config.h
--- a/libunwind/src/config.h
+++ b/libunwind/src/config.h
@@ -22,51 +22,51 @@
 
 // Platform specific configuration defines.
 #ifdef __APPLE__
-  #if defined(FOR_DYLD)
-    #define _LIBUNWIND_SUPPORT_COMPACT_UNWIND 1
-  #else
-    #define _LIBUNWIND_SUPPORT_COMPACT_UNWIND 1
-    #define _LIBUNWIND_SUPPORT_DWARF_UNWIND 1
-  #endif
+#if defined(FOR_DYLD)
+#define _LIBUNWIND_SUPPORT_COMPACT_UNWIND 1
+#else
+#define _LIBUNWIND_SUPPORT_COMPACT_UNWIND 1
+#define _LIBUNWIND_SUPPORT_DWARF_UNWIND 1
+#endif
 #elif defined(_WIN32)
-  #ifdef __SEH__
-    #define _LIBUNWIND_SUPPORT_SEH_UNWIND 1
-  #else
-    #define _LIBUNWIND_SUPPORT_DWARF_UNWIND 1
-  #endif
+#ifdef __SEH__
+#define _LIBUNWIND_SUPPORT_SEH_UNWIND 1
+#else
+#define _LIBUNWIND_SUPPORT_DWARF_UNWIND 1
+#endif
 #elif defined(_LIBUNWIND_IS_BAREMETAL)
-  #if !defined(_LIBUNWIND_ARM_EHABI)
-    #define _LIBUNWIND_SUPPORT_DWARF_UNWIND 1
-    #define _LIBUNWIND_SUPPORT_DWARF_INDEX 1
-  #endif
+#if !defined(_LIBUNWIND_ARM_EHABI)
+#define _LIBUNWIND_SUPPORT_DWARF_UNWIND 1
+#define _LIBUNWIND_SUPPORT_DWARF_INDEX 1
+#endif
 #elif defined(__BIONIC__) && defined(_LIBUNWIND_ARM_EHABI)
-  // For ARM EHABI, Bionic didn't implement dl_iterate_phdr until API 21. After
-  // API 21, dl_iterate_phdr exists, but dl_unwind_find_exidx is much faster.
-  #define _LIBUNWIND_USE_DL_UNWIND_FIND_EXIDX 1
+// For ARM EHABI, Bionic didn't implement dl_iterate_phdr until API 21. After
+// API 21, dl_iterate_phdr exists, but dl_unwind_find_exidx is much faster.
+#define _LIBUNWIND_USE_DL_UNWIND_FIND_EXIDX 1
 #elif defined(_AIX)
 // The traceback table at the end of each function is used for unwinding.
 #define _LIBUNWIND_SUPPORT_TBTAB_UNWIND 1
 #else
-  // Assume an ELF system with a dl_iterate_phdr function.
-  #define _LIBUNWIND_USE_DL_ITERATE_PHDR 1
-  #if !defined(_LIBUNWIND_ARM_EHABI)
-    #define _LIBUNWIND_SUPPORT_DWARF_UNWIND 1
-    #define _LIBUNWIND_SUPPORT_DWARF_INDEX 1
-  #endif
+// Assume an ELF system with a dl_iterate_phdr function.
+#define _LIBUNWIND_USE_DL_ITERATE_PHDR 1
+#if !defined(_LIBUNWIND_ARM_EHABI)
+#define _LIBUNWIND_SUPPORT_DWARF_UNWIND 1
+#define _LIBUNWIND_SUPPORT_DWARF_INDEX 1
+#endif
 #endif
 
 #if defined(_LIBUNWIND_HIDE_SYMBOLS)
-  // The CMake file passes -fvisibility=hidden to control ELF/Mach-O visibility.
-  #define _LIBUNWIND_EXPORT
-  #define _LIBUNWIND_HIDDEN
+// The CMake file passes -fvisibility=hidden to control ELF/Mach-O visibility.
+#define _LIBUNWIND_EXPORT
+#define _LIBUNWIND_HIDDEN
 #else
-  #if !defined(__ELF__) && !defined(__MACH__) && !defined(_AIX)
-    #define _LIBUNWIND_EXPORT __declspec(dllexport)
-    #define _LIBUNWIND_HIDDEN
-  #else
-    #define _LIBUNWIND_EXPORT __attribute__((visibility("default")))
-    #define _LIBUNWIND_HIDDEN __attribute__((visibility("hidden")))
-  #endif
+#if !defined(__ELF__) && !defined(__MACH__) && !defined(_AIX)
+#define _LIBUNWIND_EXPORT __declspec(dllexport)
+#define _LIBUNWIND_HIDDEN
+#else
+#define _LIBUNWIND_EXPORT __attribute__((visibility("default")))
+#define _LIBUNWIND_HIDDEN __attribute__((visibility("hidden")))
+#endif
 #endif
 
 #define STR(a) #a
@@ -121,10 +121,32 @@
 #endif
 #endif
 
+#if defined(__has_builtin)
+#define _LIBUNWIND_HAS_BUILTIN(x) __has_builtin(x)
+#else
+#define _LIBUNWIND_HAS_BUILTIN(x) 0
+#endif
+
+#if defined(__has_include)
+#define _LIBUNWIND_HAS_INCLUDE(x) __has_include(x)
+#else
+#define _LIBUNWIND_HAS_INCLUDE(x) 0
+#endif
+
 #ifndef _LIBUNWIND_REMEMBER_HEAP_ALLOC
-#if defined(_LIBUNWIND_REMEMBER_STACK_ALLOC) || defined(__APPLE__) ||          \
-    defined(__linux__) || defined(__ANDROID__) || defined(__MINGW32__) ||      \
-    defined(_LIBUNWIND_IS_BAREMETAL)
+
+#if _LIBUNWIND_HAS_BUILTIN(__builtin_alloca)
+#define _LIBUNWIND_REMEMBER_ALLOC(_size) __builtin_alloca(_size)
+#define _LIBUNWIND_REMEMBER_FREE(_ptr)                                         \
+  do {                                                                         \
+  } while (0)
+#elif defined(alloca)
+#define _LIBUNWIND_REMEMBER_ALLOC(_size) alloca(_size)
+#define _LIBUNWIND_REMEMBER_FREE(_ptr)                                         \
+  do {                                                                         \
+  } while (0)
+#elif _LIBUNWIND_HAS_INCLUDE(<alloca.h>)
+#include <alloca.h>
 #define _LIBUNWIND_REMEMBER_ALLOC(_size) alloca(_size)
 #define _LIBUNWIND_REMEMBER_FREE(_ptr)                                         \
   do {                                                                         \
@@ -173,52 +195,52 @@
 #endif
 
 #if defined(NDEBUG)
-  #define _LIBUNWIND_LOG_IF_FALSE(x) x
+#define _LIBUNWIND_LOG_IF_FALSE(x) x
 #else
   #define _LIBUNWIND_LOG_IF_FALSE(x)                                           \
     do {                                                                       \
       bool _ret = x;                                                           \
       if (!_ret)                                                               \
         _LIBUNWIND_LOG("" #x " failed in %s", __FUNCTION__);                   \
-    } while (0)
+  } while (0)
 #endif
 
 // Macros that define away in non-Debug builds
 #ifdef NDEBUG
-  #define _LIBUNWIND_DEBUG_LOG(msg, ...)
-  #define _LIBUNWIND_TRACE_API(msg, ...)
-  #define _LIBUNWIND_TRACING_UNWINDING (0)
-  #define _LIBUNWIND_TRACING_DWARF (0)
-  #define _LIBUNWIND_TRACE_UNWINDING(msg, ...)
-  #define _LIBUNWIND_TRACE_DWARF(...)
-#else
-  #ifdef __cplusplus
-    extern "C" {
-  #endif
+#define _LIBUNWIND_DEBUG_LOG(msg, ...)
+#define _LIBUNWIND_TRACE_API(msg, ...)
+#define _LIBUNWIND_TRACING_UNWINDING (0)
+#define _LIBUNWIND_TRACING_DWARF (0)
+#define _LIBUNWIND_TRACE_UNWINDING(msg, ...)
+#define _LIBUNWIND_TRACE_DWARF(...)
+#else
+#ifdef __cplusplus
+extern "C" {
+#endif
     extern  bool logAPIs(void);
     extern  bool logUnwinding(void);
     extern  bool logDWARF(void);
-  #ifdef __cplusplus
-    }
-  #endif
+#ifdef __cplusplus
+}
+#endif
   #define _LIBUNWIND_DEBUG_LOG(msg, ...)  _LIBUNWIND_LOG(msg, __VA_ARGS__)
   #define _LIBUNWIND_TRACE_API(msg, ...)                                       \
     do {                                                                       \
       if (logAPIs())                                                           \
         _LIBUNWIND_LOG(msg, __VA_ARGS__);                                      \
-    } while (0)
-  #define _LIBUNWIND_TRACING_UNWINDING logUnwinding()
-  #define _LIBUNWIND_TRACING_DWARF logDWARF()
+  } while (0)
+#define _LIBUNWIND_TRACING_UNWINDING logUnwinding()
+#define _LIBUNWIND_TRACING_DWARF logDWARF()
   #define _LIBUNWIND_TRACE_UNWINDING(msg, ...)                                 \
     do {                                                                       \
       if (logUnwinding())                                                      \
         _LIBUNWIND_LOG(msg, __VA_ARGS__);                                      \
-    } while (0)
+  } while (0)
   #define _LIBUNWIND_TRACE_DWARF(...)                                          \
     do {                                                                       \
       if (logDWARF())                                                          \
         fprintf(stderr, __VA_ARGS__);                                          \
-    } while (0)
+  } while (0)
 #endif
 
 #ifdef __cplusplus
@@ -234,10 +256,10 @@
   template <typename T>
   struct blk_count {
     static const size_t count =
-      (sizeof(T) + sizeof(uint64_t) - 1) / sizeof(uint64_t);
+        (sizeof(T) + sizeof(uint64_t) - 1) / sizeof(uint64_t);
   };
   static const bool does_fit =
-    (blk_count<_Type>::count COMP_OP blk_count<_Mem>::count);
+      (blk_count<_Type>::count COMP_OP blk_count<_Mem>::count);
 };
 #undef COMP_OP
 #endif // __cplusplus