Consider to using std::size_t instead of size_t

[jslee02]

Basically, they are both same, but, to be pedantic, size_t is defined in std namespace. Using std::size_t would be the consistent way as we always (at least in the headers) specify std for stl types like std::vector<...> for instance.

[mxgrey]

I am okay with pedantry 👍 .

[mkoval]

Here's what the C++ standard says:

17.4.3.1.4 Types [lib.extern.types]

For each type T from the Standard C library, the types ::T and std::T are reserved to the implementation and, when defined, ::T shall be identical to std::T.

These types are clock_t, div_t, FILE, fpos_t, lconv, ldiv_t, mbstate_t, ptrdiff_t, sig_atomic_t, size_t, time_t, tm, va_list, wctrans_t, wctype_t, and wint_t.

The ::T and std::T types are defined in different header files:

[Example: The header <cstdlib> assuredly provides its declarations and definitions within the namespace std. It may also provide these names within the global namespace. The header <stdlib.h> assuredly provides the same declarations and definitions within the global namespace, much as in the C Standard. It may also provide these names within the namespace std. — end example ]

TL;DR: We should use std::size_t if we include <cstddef> and use size_t if we include <stddef.h>. If both headers are included, then we may use either.

[mxgrey]

We've been preferring the C++ versions of headers to the exclusion of C versions, so that would imply that we should prefer std::size_t. The catch is that it seems most STL implementations do provide size_t in the global namespace in <cstddef>, so we could probably get away with continuing to use size_t even without ever using <stddef.h>, but it wouldn't be strictly guaranteed to work.

Taking all that into consideration, I would favor the side of consistency, pedantry, and guarantees (std::size_t) over shortcuts (size_t).