linux-kernel - Re: [kbuild-all] Re: [PATCH] gcov: fail build on gcov

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Date:   Mon, 15 Mar 2021 10:31:49 +0800
From:   Rong Chen <rong.a.chen@...el.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     kernel test robot <lkp@...el.com>,
        Peter Oberparleiter <oberpar@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kbuild-all@...ts.01.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [kbuild-all] Re: [PATCH] gcov: fail build on gcov_info size
 mismatch



On 3/13/21 1:52 AM, Linus Torvalds wrote:
> On Thu, Mar 11, 2021 at 7:50 PM Rong Chen <rong.a.chen@...el.com> wrote:
>>
>> The issue is from a=!, and [ "$a $b" = ".size .LPBX0," ] can avoid the
>> error.
>>
>> + [ ! = .size -a ABI = .LPBX0, ]
>> ./kernel/gcov/geninfosize.sh: 13: [: =: unexpected operator
> But that's not what the patch did.
>
> The patch used quotes around $a, so "$a" should still be fine.
>
> See:
>
>     [torvalds@...en ~]$ a="!" [ "$a" = ".size" ]
>
> is fine, but
>
>     [torvalds@...en ~]$ a="!" [ $a = ".size" ]
>     -bash: [: =: unary operator expected
>
> and the patch I saw, and that the test robot replied to, had that
> correct quoting, afaik.
>
> So I still don't see what the test robot is complaining about. Was
> there an earlier version of the patch without the quotes that I didn't
> see?
>
> Or is the shell on the test robot doing something really really odd,
> and it's somehow nds32-specific?
>
>                  Linus

Hi Linus,

It can be reproduced with '-a' option in dash:

     $ a="!"
     $ [ "$a" = ".size" ]
     $ [ "$a" = ".size" -a "$b" = ".LPBX0," ]
     sh: 2: [: =: unexpected operator

and there is a advice for the option at 
https://wiki.ubuntu.com/DashAsBinSh, I'm not sure it's the best practice 
or not.

     While dash supports most uses of the -a and -o options, they have 
very confusing semantics even in bash and are best avoided. Commands 
like the following:
         [ \( "$foo" = "$bar" -a -f /bin/baz \) -o ! -x /bin/quux ]
     should be replaced with:
         (([ "$foo" = "$bar" ] && [ -f /bin/baz ]) || [ ! -x /bin/quux ])

Best Regards,
Rong Chen