[drdaeman]

Is there anything that forbids those utilities from using system-provided headers and time_t? I think they'll build fine on any POSIX.1-compliant system then.

Unless they're doing something really weird with time_t values, I don't think there's any reason they should know whenever it's long long or int64_t or whatever under the hood.

[lmm]

printf("%lld", (int64_t) t); wouldn't build on a system that doesn't have int64_t, so one needs to use long long.

[drdaeman]

Why cast to `int64_t` here? Just because `time_t` could be `int64_t` under the hood doesn't mean it must be casted to this exact type for string formatting/presentation purposes.

And I thought `%lld` actually means `long long`... So, http://ideone.com/SJJFPs seems like a proper approach to me. That said, if compiler supports %lld (an %I64d or alike might be required for older compilers), so a better cross-compiler approach would be in lines of `printf("test: " TIME_FMT "\n", (TIME_FMT_CAST)t)`. Or, ahem, maybe, `print_time(t)`.

[lmm]

Assuming we don't want to maintain a set of per-platform macros, we need to use an existing, standard format specifier. There isn't one that takes a time_t. So we have to cast time_t to a type big enough to contain it, use the format specifier for that type, and we want this to be as cross-platform as possible, i.e. we use the oldest, most widely-supported type which can definitely hold at least 64 bits and has a standard printf specifier available. i.e. "long long", exactly as in your example code.

So that's why we prefer "long long" rather than "int64_t", which I thought was your original question.

[drdaeman]

Oh. I thought the discussion was not about what type to cast when using printf (I agree, only `%lld`/`long long` fits perfectly), but what type to use for `time_t` internally. Sorry if I misunderstood and missed the point.