Add option to gen_snapshot for creating a Makefile describing a snapshot's dependencies.

runtime/bin/file_macos.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "platform/globals.h"
 #if defined(TARGET_OS_MACOS)
 
 #include "bin/file.h"
 
 #include <copyfile.h>  // NOLINT
@@ skipping 104 matching lines @@
   return TEMP_FAILURE_RETRY(read(handle_->fd(), buffer, num_bytes));
 }
 
 
 int64_t File::Write(const void* buffer, int64_t num_bytes) {
   ASSERT(handle_->fd() >= 0);
   return TEMP_FAILURE_RETRY(write(handle_->fd(), buffer, num_bytes));
 }
 
 
+bool File::VPrint(const char* format, va_list args) {
+  // Measure.
+  va_list measure_args;
+  va_copy(measure_args, args);
+  intptr_t len = vsnprintf(NULL, 0, format, measure_args);
+  va_end(measure_args);
+
+  char* buffer = reinterpret_cast<char*>(malloc(len + 1));
+
+  // Print.
+  va_list print_args;
+  va_copy(print_args, args);
+  vsnprintf(buffer, len + 1, format, print_args);
+  va_end(print_args);
+
+  bool result = WriteFully(buffer, len);
+  free(buffer);
+  return result;
+}
+
 int64_t File::Position() {
   ASSERT(handle_->fd() >= 0);
   return lseek(handle_->fd(), 0, SEEK_CUR);
 }
 
 
 bool File::SetPosition(int64_t position) {
   ASSERT(handle_->fd() >= 0);
   return lseek(handle_->fd(), position, SEEK_SET) >= 0;
 }
@@ skipping 421 matching lines @@
   return ((file_1_info.st_ino == file_2_info.st_ino) &&
           (file_1_info.st_dev == file_2_info.st_dev))
              ? File::kIdentical
              : File::kDifferent;
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_MACOS)