Re: [PATCH v2 1/2][4.15] tools/x86: don't rebuild cpuid-autogen.h every time

[Ian Jackson <iwj@xxxxxxxxxxxxxx>]

Jan Beulich writes ("[PATCH v2 1/2][4.15] tools/x86: don't rebuild 
cpuid-autogen.h every time"):
> Ian did suggest to pass -0r to xargs (and -print0 to find), but I
> couldn't convince myself that these are standard compliant options. We
> don't use any special characters in file names, so -print0 / -0
> shouldn't be necessary at all. The stray rm invocation when there is no
> output from find can be taken care of by passing -f to it.

I addressed these portability questions in my original mail.

I said that I had checked FreeBSD find and xargs have all these
options.  I didn't check the other *BSDs but I see no reason to think
they would be different.

find -print0 and xargs -0 are not in SuS (for bad reasons) but these
are obviously necessary (unless one thinks people are supposed to use
  -exec printf "%s\n" '{}' \;
when the output is going to something more complicated an just some
command's arguments.

IOW we are IMO find to rely on both these options.

I would be OK with find -exec + in this case.  The {} must be quoted.

> --- a/tools/include/Makefile
> +++ b/tools/include/Makefile
> @@ -19,7 +19,7 @@ xen-foreign:
>       $(MAKE) -C xen-foreign
>  
>  xen-dir:
> -     @rm -rf xen acpi
> +     find xen/ acpi/ -type l 2>/dev/null | xargs rm -f --

I disapprove of the 2>/dev/null and the -f because I disapprove of
suppressing.

Ian.