Re: [PATCH] fchmodat, lchmod: port to buggy Linux filesystems

[Paul Eggert]

On 2/13/20 7:46 PM, Bruno Haible wrote:

> Here is a proposed patch:

Thanks, looks good.

> 2) Also the discussion what is the "right" behaviour is specific to Linux.
> The code in the '#else' case
>
>    if (S_ISLNK (st.st_mode))
>      {
>        close (fd);
>        errno = EOPNOTSUPP;
>        return -1;
>      }
>
> will surely upset users on BSD systems, where symlinks are intended to have
> permission bits.

Because of the Autoconf tests, that code should be executed only on 
platforms where lchmod fails (or does not exist), whould shouldn't occur 
on BSD systems. Still, I take your point that the code is confusing. 
Perhaps lchmod.m4 and fchmodat.m4 should define a symbol 
HAVE_LCHMOD_BUG_WITH_NON_SYMLINKS and the C code could refer to that. 
The resulting machine code would be the same as now, but the 
cause-and-effect would be clearer.