Uses SNPRINT macro where possible. Otherwise uses #define for format.

runtime/vm/zone.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 "vm/zone.h"
 
 #include "platform/assert.h"
 #include "platform/utils.h"
 #include "vm/flags.h"
 #include "vm/handles_impl.h"
@@ skipping 185 matching lines @@
   while (zone != NULL) {
     zone->handles()->VisitObjectPointers(visitor);
     zone = zone->previous_;
   }
 }
 
 
 char* Zone::PrintToString(const char* format, ...) {
   va_list args;
   va_start(args, format);
-  return VPrint(format, args);
+  char* buffer = OS::VSCreate(this, format, args);
+  va_end(args);
+  return buffer;
 }
 
 
 char* Zone::VPrint(const char* format, va_list args) {
-  // Measure.
-  va_list measure_args;
-  va_copy(measure_args, args);
-  intptr_t len = OS::VSNPrint(NULL, 0, format, measure_args);
-  va_end(measure_args);
-
-  // Print.
-  char* buffer = Alloc<char>(len + 1);
-  va_list print_args;
-  va_copy(print_args, args);
-  OS::VSNPrint(buffer, (len + 1), format, print_args);
-  va_end(print_args);
-  return buffer;
+  return OS::VSCreate(this, format, args);
 }
 
 
 }  // namespace dart