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This is probably a C++ 101 question: I'm curious what the guidelines are for using size_t and offset_t, e.g. what situations they are intended for, what situations they are not intended for, etc. I haven't done a lot of portable programming, so I have typically just used something like int or unsigned int for array sizes, indexes, and the like. However, I gather it's preferable to use some of these more standard typedefs when possible, so I'd like to know how to do that properly.
As a follow-up question, for development on Windows using Visual Studio 2008, where should I look to find the actual typedefs? I've found size_t defined in a number of headers within the VS installation directory, so I'm not sure which of those I should use, and I can't find offset_t anywhere.
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size_t is commonly used for array indexing and loop counting. Programs that use other types, such as unsigned int, for array indexing may fail on, e.g. 64-bit systems when the index exceeds UINT_MAX or if it relies on 32-bit modular arithmetic.
So yeah, both are same; the only difference is that C++ defines size_t in std namespace.
size_t type is a base unsigned integer type of C/C++ language. It is the type of the result returned by sizeof operator. The type's size is chosen so that it can store the maximum size of a theoretically possible array of any type. On a 32-bit system size_t will take 32 bits, on a 64-bit one 64 bits.
You are probably referring to off_t, not offset_t. off_t is a POSIX type, not a C type, and it is used to denote file offsets (allowing 64-bit file offsets even on 32-bit systems). C99 has superceded that with fpos_t.
size_t is meant to count bytes or array elements. It matches the address space.
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