PVS-Studio warning V611 for libstagefright

AString StringPrintf(const char *format, ...) {
  va_list ap;
  va_start(ap, format);

  char *buffer;
#ifdef _MSC_VER
  int n = vsnprintf(NULL, 0, format, ap);
  buffer = new char[n+1];                    <<<<====
  vsnprintf(buffer, n+1, format, ap);
#else
  vasprintf(&buffer, format, ap);
#endif
  va_end(ap);

  AString result(buffer);

  free(buffer);                              <<<<====
  buffer = NULL;

  return result;
}

This suspicious code was found in libstagefright project by PVS-Studio static code analyzer.
Warning message is:
V611 The memory was allocated using 'new' operator but was released using the 'free' function. Consider inspecting operation logics behind the 'buffer' variable. astring.cpp 340

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