Why would uint32_t be preferred rather than uint_fast32_t?

Question

It seems that uint32_t is much more prevalent than uint_fast32_t (I realise this is anecdotal evidence). That seems counter-intuitive to me, though.

Answer 1

Why do many people use uint32_t rather than uint32_fast_t?

Silly answer:

• There is no standard type uint32_fast_t, the correct spelling is uint_fast32_t.

Practical answer:

• Many people actually use uint32_t or int32_t for their precise semantics, exactly 32 bits with unsigned wrap around arithmetic (uint32_t) or 2's complement representation (int32_t). The xxx_fast32_t types may be larger and thus inappropriate to store to binary files, use in packed arrays and structures, or send over a network. Furthermore, they may not even be faster.

Pragmatic answer:

• Many people just don't know (or simply don't care) about uint_fast32_t, as demonstrated in comments and answers, and probably assume plain unsigned int to have the same semantics, although many current architectures still have 16-bit ints and some rare Museum samples have other strange int sizes less than 32.

UX answer:

• Although possibly faster than uint32_t, uint_fast32_t is slower to use: it takes longer to type, especially accounting for looking up spelling and semantics in the C documentation ;-)

Elegance matters, (obviously opinion based):

• uint32_t looks bad enough that many programmers prefer to define their own u32 or uint32 type... From this perspective, uint_fast32_t looks clumsy beyond repair. No surprise it sits on the bench with its friends uint_least32_t and such.