[cbsmith]

> Using a macro for the format specifier would require defining such a macro on other systems, because they have to be able to compile much of this code on Linux, OS X, or even Windows in some cases.

    #ifdef LONG_LONG_TIME_T
    #define PRI_TIME_T "lld"
    #else
    #define PRI_TIME_T "ld"
    #endif

There, I just made it so that you can do:

    time_t x = ...;
    printf("%" PRI_TIME_T "\n", x);

I don't much like how it looks, but it works and it'd be easy to make portable code with it. All you need is a preprocessor flag to indicate when you were using long long.

The real problem is that it'd be easier to get old embedded systems upgraded to 64-bit in the next 25 years than to get those old systems retrofitted with such an annoying syntax. Forcing everything to a know and use a "wide enough" integer width is probably the best you can really do with format strings anyway.

[lmm]

And you repeat that macro in every file? Or you assume you can somehow persuade other OSes to add it to their headers?

printf("%lld\n", (long long) x); is ugly but it works on every system, including existing systems with 32-bit time_t that don't make any changes to their headers.

[cbsmith]

> And you repeat that macro in every file?

You are familiar with the concept of headers, right? ;-)

Just put that in the project's common header (which if it is dealing with so many different OS's, invariably already have a bunch of platform abstractions). I deliberately structured the solution so the only "extra work" that is needed is for whatever platform has created a long long time_t (and if you really wanted to, you could probably get rid of even that work and base the entire thing off of sizeof(long long) even without using something like autoconf).

> printf("%lld\n", (long long) x); is ugly

Wow, we couldn't be of more different opinions. I'd argue the virtue of that approach is it is less ugly are more likely to be easily accepted as a change for crufty old 32-bit code in some embedded system that everyone has forgotten about.