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

runtime/vm/os.h

 // Copyright (c) 2011, 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.
 
 #ifndef VM_OS_H_
 #define VM_OS_H_
 
 #include "vm/globals.h"
 
+
 // Forward declarations.
 struct tm;
 
 namespace dart {
 
 // Forward declarations.
 class Isolate;
+class Zone;
 
 // Interface to the underlying OS platform.
 class OS {
  public:
   // Returns the name of the given OS. For example "linux".
   static const char* Name();
 
   // Returns the current process id.
   static intptr_t ProcessId();
 
@@ skipping 86 matching lines @@
   // This specification conforms to C99 standard which is implemented
   // by glibc 2.1+ with one exception: the C99 standard allows a
   // negative return value.  We will terminate the vm rather than let
   // that occur.
   static int SNPrint(char* str, size_t size, const char* format, ...)
       PRINTF_ATTRIBUTE(3, 4);
   static int VSNPrint(char* str, size_t size,
                       const char* format,
                       va_list args);
 
+  // Allocate a string and print formatted output into the buffer.
+  // Uses the zone for allocation if one if provided, and otherwise uses
+  // malloc.
+  static char* SNCreate(Zone* zone, const char* format, ...)
+      PRINTF_ATTRIBUTE(2, 3);
+
   // Converts a C string which represents a valid dart integer into a 64 bit
   // value.
   // Returns false if it is unable to convert the string to a 64 bit value,
   // the failure could be because of underflow/overflow or invalid characters.
   // On success the function returns true and 'value' contains the converted
   // value.
   static bool StringToInt64(const char* str, int64_t* value);
 
   // Register code observers relevant to this OS.
   static void RegisterCodeObservers();
 
   // Initialize the OS class.
   static void InitOnce();
 
   // Shut down the OS class.
   static void Shutdown();
 
   static void Abort();
 
   static void Exit(int code);
 };
 
 }  // namespace dart
 
 #endif  // VM_OS_H_