[PATCH] skip testing time before epoch on mips

[YunQiang Su]

Chen Li <chenli@uniontech.com> 于2021年3月8日周一 下午2:35写道：
>
>
> When execute libstdc++ testcases on mips, I notice that last_write_time
> alawys failed, and the failed VERIFY is  "VERIFY(
> approx_equal(last_write_time(f.path), time) );" where testing time before
> than epoch.
>
> Below is the minimal case:
>
> ```
> // gcc a.c
> int main()
> {
>         struct timespec times[2] = {{1, UTIME_OMIT}, {-1201, 985000000}};
>         utimensat(AT_FDCWD, "test", times, 0);
>
> }
> ```
>
> $ touch test && gcc a.c && ./a.out && stat test
>   File: test
>   Size: 0               Blocks: 0          IO Block: 4096   regular empty file
> Device: 805h/2053d      Inode: 1056841     Links: 1
> Access: (0644/-rw-r--r--)  Uid: ( 1000/  deepin)   Gid: ( 1000/  deepin)
> Access: 2021-03-08 13:52:55.966354501 +0800
> Modify: 2106-02-07 14:08:15.985000000 +0800
> Change: 2021-03-08 13:52:56.907782193 +0800
>  Birth: -
>
> Undoubtedly, mtime's type is unsigned somewhere on mips.
>

It only has this problem on mips64.

https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=983769

> After debuging kernel, it turns out that mtime is always -1201 in
> ext4_setattr, cp_new_stat, newlstat and etc, so the problem should not
> occur in kernel space.
>
> go back to user space via copy_to_user, I finally found mips used
> "unsigned int st_mtime_sec;" in struct kernel_stat, which is used to
> receive -1201 from kernel.
>
> Maybe sparc also suffers from this problem, but I have no machine to
> verify.
> ---
>  .../testsuite/27_io/filesystem/operations/last_write_time.cc    | 2 ++
>  .../experimental/filesystem/operations/last_write_time.cc       | 2 ++
>  2 files changed, 4 insertions(+)
>
> diff --git a/libstdc++-v3/testsuite/27_io/filesystem/operations/last_write_time.cc b/libstdc++-v3/testsuite/27_io/filesystem/operations/last_write_time.cc
> index 6ae64c482b6..72272d4e781 100644
> --- a/libstdc++-v3/testsuite/27_io/filesystem/operations/last_write_time.cc
> +++ b/libstdc++-v3/testsuite/27_io/filesystem/operations/last_write_time.cc
> @@ -200,11 +200,13 @@ test02()
>    VERIFY( approx_equal(last_write_time(f.path), time) );
>
>    ec = bad_ec;
> +  #ifndef __mips__
>    // A time before than the epoch
>    time -= chrono::milliseconds(1000 * 60 * 20 + 15);
>    last_write_time(f.path, time, ec);
>    VERIFY( !ec );
>    VERIFY( approx_equal(last_write_time(f.path), time) );
> +  #endif
>  }
>
>  int
> diff --git a/libstdc++-v3/testsuite/experimental/filesystem/operations/last_write_time.cc b/libstdc++-v3/testsuite/experimental/filesystem/operations/last_write_time.cc
> index 536ab1f28f6..6fb490a6bc3 100644
> --- a/libstdc++-v3/testsuite/experimental/filesystem/operations/last_write_time.cc
> +++ b/libstdc++-v3/testsuite/experimental/filesystem/operations/last_write_time.cc
> @@ -165,11 +165,13 @@ test02()
>    VERIFY( !ec );
>    VERIFY( approx_equal(last_write_time(f.path), time) );
>
> +  #ifndef __mips__
>    ec = bad_ec;
>    time -= chrono::milliseconds(1000 * 60 * 10 + 15);
>    last_write_time(f.path, time, ec);
>    VERIFY( !ec );
>    VERIFY( approx_equal(last_write_time(f.path), time) );
> +  #endif
>  }
>
>  int
> --
> 2.30.0
>
>
>


-- 
YunQiang Su