diff --git a/libcxxabi/.clang-format b/libcxxabi/.clang-format
new file mode 100644
index 000000000000..2d1d3bee68f5
--- /dev/null
+++ b/libcxxabi/.clang-format
@@ -0,0 +1,12 @@
+BasedOnStyle: LLVM
+
+---
+Language: Cpp
+
+AlwaysBreakTemplateDeclarations: true
+PointerAlignment: Left
+
+# Disable formatting options which may break tests.
+SortIncludes: false
+ReflowComments: false
+---
diff --git a/libcxxabi/src/fallback_malloc.cpp b/libcxxabi/src/fallback_malloc.cpp
index 31911bdb754f..2631c9bdce2d 100644
--- a/libcxxabi/src/fallback_malloc.cpp
+++ b/libcxxabi/src/fallback_malloc.cpp
@@ -32,216 +32,222 @@ namespace {
 _LIBCPP_SAFE_STATIC
 static std::__libcpp_mutex_t heap_mutex = _LIBCPP_MUTEX_INITIALIZER;
 #else
-static void * heap_mutex = 0;
+static void* heap_mutex = 0;
 #endif
 
 class mutexor {
 public:
 #ifndef _LIBCXXABI_HAS_NO_THREADS
-    mutexor ( std::__libcpp_mutex_t *m ) : mtx_(m) {
-      std::__libcpp_mutex_lock ( mtx_ );
-    }
-    ~mutexor () { std::__libcpp_mutex_unlock ( mtx_ ); }
+  mutexor(std::__libcpp_mutex_t* m) : mtx_(m) {
+    std::__libcpp_mutex_lock(mtx_);
+  }
+  ~mutexor() { std::__libcpp_mutex_unlock(mtx_); }
 #else
-    mutexor ( void * ) {}
-    ~mutexor () {}
+  mutexor(void*) {}
+  ~mutexor() {}
 #endif
 private:
-    mutexor ( const mutexor &rhs );
-    mutexor & operator = ( const mutexor &rhs );
+  mutexor(const mutexor& rhs);
+  mutexor& operator=(const mutexor& rhs);
 #ifndef _LIBCXXABI_HAS_NO_THREADS
-    std::__libcpp_mutex_t *mtx_;
+  std::__libcpp_mutex_t* mtx_;
 #endif
 };
 
-
 static const size_t HEAP_SIZE = 512;
-char heap [ HEAP_SIZE ] __attribute__((aligned));
+char heap[HEAP_SIZE] __attribute__((aligned));
 
 typedef unsigned short heap_offset;
 typedef unsigned short heap_size;
 
 struct heap_node {
-    heap_offset next_node;  // offset into heap
-    heap_size   len;        // size in units of "sizeof(heap_node)"
+  heap_offset next_node; // offset into heap
+  heap_size len;         // size in units of "sizeof(heap_node)"
 };
 
-static const heap_node *list_end = (heap_node *) ( &heap [ HEAP_SIZE ] );   // one past the end of the heap
-static heap_node *freelist = NULL;
+static const heap_node* list_end =
+    (heap_node*)(&heap[HEAP_SIZE]); // one past the end of the heap
+static heap_node* freelist = NULL;
 
-heap_node *node_from_offset ( const heap_offset offset )
-    { return (heap_node *) ( heap + ( offset * sizeof (heap_node))); }
+heap_node* node_from_offset(const heap_offset offset) {
+  return (heap_node*)(heap + (offset * sizeof(heap_node)));
+}
 
-heap_offset offset_from_node ( const heap_node *ptr )
-    { return static_cast<heap_offset>(static_cast<size_t>(reinterpret_cast<const char *>(ptr) - heap)  / sizeof (heap_node)); }
+heap_offset offset_from_node(const heap_node* ptr) {
+  return static_cast<heap_offset>(
+      static_cast<size_t>(reinterpret_cast<const char*>(ptr) - heap) /
+      sizeof(heap_node));
+}
 
-void init_heap () {
-    freelist = (heap_node *) heap;
-    freelist->next_node = offset_from_node ( list_end );
-    freelist->len = HEAP_SIZE / sizeof (heap_node);
-    }
+void init_heap() {
+  freelist = (heap_node*)heap;
+  freelist->next_node = offset_from_node(list_end);
+  freelist->len = HEAP_SIZE / sizeof(heap_node);
+}
 
 //  How big a chunk we allocate
-size_t alloc_size (size_t len)
-    { return (len + sizeof(heap_node) - 1) / sizeof(heap_node) + 1; }
+size_t alloc_size(size_t len) {
+  return (len + sizeof(heap_node) - 1) / sizeof(heap_node) + 1;
+}
 
-bool is_fallback_ptr ( void *ptr )
-    { return ptr >= heap && ptr < ( heap + HEAP_SIZE ); }
+bool is_fallback_ptr(void* ptr) {
+  return ptr >= heap && ptr < (heap + HEAP_SIZE);
+}
 
-void *fallback_malloc(size_t len) {
-    heap_node *p, *prev;
-    const size_t nelems = alloc_size ( len );
-    mutexor mtx ( &heap_mutex );
+void* fallback_malloc(size_t len) {
+  heap_node *p, *prev;
+  const size_t nelems = alloc_size(len);
+  mutexor mtx(&heap_mutex);
 
-    if ( NULL == freelist )
-        init_heap ();
+  if (NULL == freelist)
+    init_heap();
 
-//  Walk the free list, looking for a "big enough" chunk
-    for (p = freelist, prev = 0;
-            p && p != list_end;     prev = p, p = node_from_offset ( p->next_node)) {
+  //  Walk the free list, looking for a "big enough" chunk
+  for (p = freelist, prev = 0; p && p != list_end;
+       prev = p, p = node_from_offset(p->next_node)) {
 
-        if (p->len > nelems) {  //  chunk is larger, shorten, and return the tail
-            heap_node *q;
+    if (p->len > nelems) { //  chunk is larger, shorten, and return the tail
+      heap_node* q;
 
-            p->len = static_cast<heap_size>(p->len - nelems);
-            q = p + p->len;
-            q->next_node = 0;
-            q->len = static_cast<heap_size>(nelems);
-            return (void *) (q + 1);
-        }
-
-        if (p->len == nelems) { // exact size match
-            if (prev == 0)
-                freelist = node_from_offset(p->next_node);
-            else
-                prev->next_node = p->next_node;
-            p->next_node = 0;
-            return (void *) (p + 1);
-        }
+      p->len = static_cast<heap_size>(p->len - nelems);
+      q = p + p->len;
+      q->next_node = 0;
+      q->len = static_cast<heap_size>(nelems);
+      return (void*)(q + 1);
     }
-    return NULL;    // couldn't find a spot big enough
+
+    if (p->len == nelems) { // exact size match
+      if (prev == 0)
+        freelist = node_from_offset(p->next_node);
+      else
+        prev->next_node = p->next_node;
+      p->next_node = 0;
+      return (void*)(p + 1);
+    }
+  }
+  return NULL; // couldn't find a spot big enough
 }
 
 //  Return the start of the next block
-heap_node *after ( struct heap_node *p ) { return p + p->len; }
+heap_node* after(struct heap_node* p) { return p + p->len; }
 
-void fallback_free (void *ptr) {
-    struct heap_node *cp = ((struct heap_node *) ptr) - 1;      // retrieve the chunk
-    struct heap_node *p, *prev;
+void fallback_free(void* ptr) {
+  struct heap_node* cp = ((struct heap_node*)ptr) - 1; // retrieve the chunk
+  struct heap_node *p, *prev;
 
-    mutexor mtx ( &heap_mutex );
+  mutexor mtx(&heap_mutex);
 
 #ifdef DEBUG_FALLBACK_MALLOC
-        std::cout << "Freeing item at " << offset_from_node ( cp ) << " of size " << cp->len << std::endl;
+  std::cout << "Freeing item at " << offset_from_node(cp) << " of size "
+            << cp->len << std::endl;
 #endif
 
-    for (p = freelist, prev = 0;
-            p && p != list_end;     prev = p, p = node_from_offset (p->next_node)) {
+  for (p = freelist, prev = 0; p && p != list_end;
+       prev = p, p = node_from_offset(p->next_node)) {
 #ifdef DEBUG_FALLBACK_MALLOC
-        std::cout << "  p, cp, after (p), after(cp) "
-            << offset_from_node ( p ) << ' '
-            << offset_from_node ( cp ) << ' '
-            << offset_from_node ( after ( p )) << ' '
-            << offset_from_node ( after ( cp )) << std::endl;
+    std::cout << "  p, cp, after (p), after(cp) " << offset_from_node(p) << ' '
+              << offset_from_node(cp) << ' ' << offset_from_node(after(p))
+              << ' ' << offset_from_node(after(cp)) << std::endl;
 #endif
-        if ( after ( p ) == cp ) {
+    if (after(p) == cp) {
 #ifdef DEBUG_FALLBACK_MALLOC
-            std::cout << "  Appending onto chunk at " << offset_from_node ( p ) << std::endl;
+      std::cout << "  Appending onto chunk at " << offset_from_node(p)
+                << std::endl;
 #endif
-            p->len = static_cast<heap_size>(p->len + cp->len);  // make the free heap_node larger
-            return;
-            }
-        else if ( after ( cp ) == p ) { // there's a free heap_node right after
+      p->len = static_cast<heap_size>(
+          p->len + cp->len); // make the free heap_node larger
+      return;
+    } else if (after(cp) == p) { // there's a free heap_node right after
 #ifdef DEBUG_FALLBACK_MALLOC
-            std::cout << "  Appending free chunk at " << offset_from_node ( p ) << std::endl;
+      std::cout << "  Appending free chunk at " << offset_from_node(p)
+                << std::endl;
 #endif
-            cp->len = static_cast<heap_size>(cp->len + p->len);
-            if ( prev == 0 ) {
-                freelist = cp;
-                cp->next_node = p->next_node;
-                }
-            else
-                prev->next_node = offset_from_node(cp);
-            return;
-            }
-        }
+      cp->len = static_cast<heap_size>(cp->len + p->len);
+      if (prev == 0) {
+        freelist = cp;
+        cp->next_node = p->next_node;
+      } else
+        prev->next_node = offset_from_node(cp);
+      return;
+    }
+  }
 //  Nothing to merge with, add it to the start of the free list
 #ifdef DEBUG_FALLBACK_MALLOC
-            std::cout << "  Making new free list entry " << offset_from_node ( cp ) << std::endl;
+  std::cout << "  Making new free list entry " << offset_from_node(cp)
+            << std::endl;
 #endif
-    cp->next_node = offset_from_node ( freelist );
-    freelist = cp;
+  cp->next_node = offset_from_node(freelist);
+  freelist = cp;
 }
 
 #ifdef INSTRUMENT_FALLBACK_MALLOC
-size_t print_free_list () {
-    struct heap_node *p, *prev;
-    heap_size total_free = 0;
-    if ( NULL == freelist )
-        init_heap ();
+size_t print_free_list() {
+  struct heap_node *p, *prev;
+  heap_size total_free = 0;
+  if (NULL == freelist)
+    init_heap();
 
-    for (p = freelist, prev = 0;
-            p && p != list_end;     prev = p, p = node_from_offset (p->next_node)) {
-        std::cout << ( prev == 0 ? "" : "  ")  << "Offset: " << offset_from_node ( p )
-                << "\tsize: " << p->len << " Next: " << p->next_node << std::endl;
-        total_free += p->len;
-        }
-    std::cout << "Total Free space: " << total_free << std::endl;
-    return total_free;
-    }
+  for (p = freelist, prev = 0; p && p != list_end;
+       prev = p, p = node_from_offset(p->next_node)) {
+    std::cout << (prev == 0 ? "" : "  ") << "Offset: " << offset_from_node(p)
+              << "\tsize: " << p->len << " Next: " << p->next_node << std::endl;
+    total_free += p->len;
+  }
+  std::cout << "Total Free space: " << total_free << std::endl;
+  return total_free;
+}
 #endif
-}  // end unnamed namespace
+} // end unnamed namespace
 
 namespace __cxxabiv1 {
 
-struct __attribute__((aligned)) __aligned_type  {};
+struct __attribute__((aligned)) __aligned_type {};
 
-void * __aligned_malloc_with_fallback(size_t size) {
+void* __aligned_malloc_with_fallback(size_t size) {
 #if defined(_WIN32)
-    if (void *dest = _aligned_malloc(size, alignof(__aligned_type)))
-      return dest;
+  if (void* dest = _aligned_malloc(size, alignof(__aligned_type)))
+    return dest;
 #elif defined(_LIBCPP_HAS_NO_ALIGNED_ALLOCATION)
-    if (void* dest = std::malloc(size))
-      return dest;
+  if (void* dest = std::malloc(size))
+    return dest;
 #else
-    if (size == 0)
-        size = 1;
-    void* dest;
-    if (::posix_memalign(&dest, alignof(__aligned_type), size) == 0)
-        return dest;
+  if (size == 0)
+    size = 1;
+  void* dest;
+  if (::posix_memalign(&dest, alignof(__aligned_type), size) == 0)
+    return dest;
 #endif
-    return fallback_malloc(size);
+  return fallback_malloc(size);
 }
 
-
-void * __calloc_with_fallback(size_t count, size_t size) {
-    void *ptr = std::calloc(count, size);
-    if (NULL != ptr)
-        return ptr;
-    // if calloc fails, fall back to emergency stash
-    ptr = fallback_malloc(size * count);
-    if (NULL != ptr)
-        std::memset(ptr, 0, size * count);
+void* __calloc_with_fallback(size_t count, size_t size) {
+  void* ptr = std::calloc(count, size);
+  if (NULL != ptr)
     return ptr;
+  // if calloc fails, fall back to emergency stash
+  ptr = fallback_malloc(size * count);
+  if (NULL != ptr)
+    std::memset(ptr, 0, size * count);
+  return ptr;
 }
 
 void __aligned_free_with_fallback(void* ptr) {
   if (is_fallback_ptr(ptr))
-        fallback_free(ptr);
+    fallback_free(ptr);
   else {
 #if defined(_WIN32)
-        ::_aligned_free(ptr);
+    ::_aligned_free(ptr);
 #else
-        std::free(ptr);
+    std::free(ptr);
 #endif
   }
 }
 
-void __free_with_fallback(void *ptr) {
-    if (is_fallback_ptr(ptr))
-        fallback_free(ptr);
-    else
-        std::free(ptr);
+void __free_with_fallback(void* ptr) {
+  if (is_fallback_ptr(ptr))
+    fallback_free(ptr);
+  else
+    std::free(ptr);
 }
 
 } // namespace __cxxabiv1