Re: [PATCH v3 4/4] io: Adapt to >= 64-bit time_t

["Darrick J. Wong" <djwong@kernel.org>]

On Fri, Dec 15, 2023 at 01:36:43AM +0000, Sam James wrote:
> We now require (at least) 64-bit time_t, so we need to adjust some printf
> specifiers accordingly.
> 
> Unfortunately, we've stumbled upon a ridiculous C mmoment whereby there's

Plenty of those to go around...

> no neat format specifier (not even one of the inttypes ones) for time_t, so
> we cast to intmax_t and use %jd.
> 
> Signed-off-by: Sam James <sam@gentoo.org>
> ---
> v3: uintmax_t -> intmax_t as time_t is signed
> 
>  io/stat.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/io/stat.c b/io/stat.c
> index e8f68dc3..743a7586 100644
> --- a/io/stat.c
> +++ b/io/stat.c
> @@ -66,11 +66,11 @@ dump_raw_stat(struct stat *st)
>  	printf("stat.ino = %llu\n", (unsigned long long)st->st_ino);
>  	printf("stat.size = %lld\n", (long long)st->st_size);
>  	printf("stat.blocks = %lld\n", (long long)st->st_blocks);
> -	printf("stat.atime.tv_sec = %ld\n", st->st_atim.tv_sec);
> +	printf("stat.atime.tv_sec = %jd\n", (intmax_t)st->st_atim.tv_sec);

I almost wonder if we want a similar
BUILD_BUG_ON(sizeof(time_t) < 8);
here or something?

Also I totally didn't realize that "intmax_t" is actually s64 on x86_64.
I saw "int" and assumed "still 32-bit".

But, I guess C99 says "...capable of representing any value of any basic
signed integer type supported by the implementation."

So it apparently works even for 32-bit compilers, at least according to
godbolt.org...
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D


>  	printf("stat.atime.tv_nsec = %ld\n", st->st_atim.tv_nsec);
> -	printf("stat.ctime.tv_sec = %ld\n", st->st_ctim.tv_sec);
> +	printf("stat.ctime.tv_sec = %jd\n", (intmax_t)st->st_ctim.tv_sec);
>  	printf("stat.ctime.tv_nsec = %ld\n", st->st_ctim.tv_nsec);
> -	printf("stat.mtime.tv_sec = %ld\n", st->st_mtim.tv_sec);
> +	printf("stat.mtime.tv_sec = %jd\n", (intmax_t)st->st_mtim.tv_sec);
>  	printf("stat.mtime.tv_nsec = %ld\n", st->st_mtim.tv_nsec);
>  	printf("stat.rdev_major = %u\n", major(st->st_rdev));
>  	printf("stat.rdev_minor = %u\n", minor(st->st_rdev));
> -- 
> 2.43.0
> 
>