[klibc] mips64el stat/time/…? problem

[Arnd Bergmann]

On Tue, Jan 3, 2023, at 17:47, Thorsten Glaser wrote:
> Hi,
>
> I noticed a failure of mksh built with klibc on mips64el.
>
> The failing test, on a high level, is this:
>
> 	:>a
> 	sleep 2
> 	:>b
> 	test a -nt b
> 	echo $?
>
> This is supposed to echo 1 (false) because a is not newer than b.
>
> The test code is roughly:
>
> // const char *opnd1 = "a";
> // const char *opnd2 = "b";
> // struct stat b1, b2;
> // int s;
>
> 	return (test_stat(opnd1, &b1) == 0 &&
> 	    (((s = test_stat(opnd2, &b2)) == 0 &&
> 	    mtimecmp(&b1, &b2) > 0) || s < 0));
>
> // #define st_mtimensec st_mtim.tv_nsec
> // #define HAVE_ST_MTIMENSEC 1
>
> static int
> mtimecmp(const struct stat *sb1, const struct stat *sb2)
> {
> 	if (sb1->st_mtime < sb2->st_mtime)
> 		return (-1);
> 	if (sb1->st_mtime > sb2->st_mtime)
> 		return (1);
> #if HAVE_ST_MTIMENSEC
> 	if (sb1->st_mtimensec < sb2->st_mtimensec)
> 		return (-1);
> 	if (sb1->st_mtimensec > sb2->st_mtimensec)
> 		return (1);
> #endif
> 	return (0);
> }
>
> The build+test was on mipsel-osuosl-03.debian.org with uname -a:
>> Linux mipsel-osuosl-03 5.10.0-20-loongson-3 #1 SMP PREEMPT Debian 5.10.158-2 (2022-12-13) mips64 GNU/Linux
>
> On the same machine and during the same build, the test passed
> with glibc, musl and dietlibc.
>
> Does this suffice to begin debugging?

I don't yet see what the problem is, but it's worth noting that
mips64 is the only architecture using 'unsigned int' for the
st_mtime field, while everything else uses 'long'. There is
a good chance that the different type causes this problem.

     Arnd