Use v8::ArrayBuffer::Allocator::NewDefaultAllocator if available

It isn't provided by older (still supported) versions of V8, keep using the shim in that case.

config.m4

@@ -174,6 +174,23 @@ int main ()
   V8_SEARCH_BLOB([snapshot_blob.bin], [PHP_V8_SNAPSHOT_BLOB_PATH])
 
 
+  dnl
+  dnl  Check for v8::ArrayBuffer::Allocator::NewDefaultAllocator
+  dnl
+  AC_CACHE_CHECK([for v8::ArrayBuffer::Allocator::NewDefaultAllocator], ac_cv_has_default_allocator, [
+    AC_LINK_IFELSE([AC_LANG_PROGRAM([
+      #include <v8.h>
+    ], [ v8::ArrayBuffer::Allocator::NewDefaultAllocator(); ])], [
+      ac_cv_has_default_allocator=yes
+    ], [ 
+      ac_cv_has_default_allocator=no
+    ])
+  ])
+  if test "x$ac_cv_has_default_allocator" = "xno"; then
+    AC_DEFINE([USE_INTERNAL_ALLOCATOR], [1],
+              [Define unless v8::ArrayBuffer::Allocator::NewDefaultAllocator is usable.])
+  fi
+
   AC_LANG_RESTORE
   LIBS=$old_LIBS
   LDFLAGS="$old_LDFLAGS"

v8js_class.cc

@@ -71,6 +71,7 @@ struct v8js_jsext {
 };
 /* }}} */
 
+#ifdef USE_INTERNAL_ALLOCATOR
 class ArrayBufferAllocator : public v8::ArrayBuffer::Allocator {
 public:
 	virtual void* Allocate(size_t length) {
@@ -80,6 +81,7 @@ public:
 	virtual void* AllocateUninitialized(size_t length) { return malloc(length); }
 	virtual void Free(void* data, size_t) { free(data); }
 };
+#endif  /** USE_INTERNAL_ALLOCATOR */
 
 
 static void v8js_free_storage(zend_object *object) /* {{{ */
@@ -201,6 +203,10 @@ static void v8js_free_storage(zend_object *object) /* {{{ */
 	c->modules_base.~vector();
 
 	zval_ptr_dtor(&c->zval_snapshot_blob);
+
+#ifndef USE_INTERNAL_ALLOCATOR
+	delete c->create_params.array_buffer_allocator;
+#endif
 }
 /* }}} */
 
@@ -353,8 +359,12 @@ static PHP_METHOD(V8Js, __construct)
 
 	new (&c->create_params) v8::Isolate::CreateParams();
 
+#ifdef USE_INTERNAL_ALLOCATOR
 	static ArrayBufferAllocator array_buffer_allocator;
 	c->create_params.array_buffer_allocator = &array_buffer_allocator;
+#else
+	c->create_params.array_buffer_allocator = v8::ArrayBuffer::Allocator::NewDefaultAllocator();
+#endif
 
 	new (&c->snapshot_blob) v8::StartupData();
 	if (snapshot_blob) {