define max length for allocator

[George2]

Hello everyone,


In MSDN length_error sample,

http://msdn2.microsoft.com/en-us/library/2af6btx2.aspx

it uses internal macro _SIZT, other than size_t. I have found in file xmemory, _SIZT is defined to size_t.

So, my questions are

1. why not use size_t directly, why use an internal name (begins with _)?

2. Do we have to use _SIZT when we define a customized allocator?


thanks in advance,
George