Is size_t the word size?

Question

Is size_t the word size of the machine that compiled the code?

Parsing with g++, my compiler views size_t as an long unsigned int

Answer 1

Although the definition does not directly state what type exactly size_t is, and does not even require a minimum size, it indirectly gives some good hints. A size_t must be able to contain the size in bytes of any object, in other words, it must be able to contain the size of the largest possible object.

The largest possible object is an array (or structure) with a size equal to the entire available address space. It is not possible to reference a larger object in a meaningful manner, and apart from the availability of swap space there is no reason why it should need to be any smaller.

Therefore, by the wording of the definition, size_t must be at least 32 bits on a 32 bit architecture, and at least 64 bits on a 64 bit system. It is of course possible for an implementation to choose a larger size_t, but this is not usually the case.