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Re: [PATCH] iotests: Fix nonportable use of od --endian


From: Max Reitz
Subject: Re: [PATCH] iotests: Fix nonportable use of od --endian
Date: Tue, 25 Feb 2020 18:43:45 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1

On 19.02.20 15:41, Eric Blake wrote:
> Tests 261 and 272 fail on RHEL 7 with coreutils 8.22, since od
> --endian was not added until coreutils 8.23.  Fix this by manually
> constructing the final value one byte at a time.
> 
> Fixes: fc8ba423
> Reported-by: Andrey Shinkevich <address@hidden>
> Signed-off-by: Eric Blake <address@hidden>
> ---
>  tests/qemu-iotests/common.rc | 22 +++++++++++++++++-----
>  1 file changed, 17 insertions(+), 5 deletions(-)
> 
> diff --git a/tests/qemu-iotests/common.rc b/tests/qemu-iotests/common.rc
> index 8a6366c09daf..b77ef3d22cd1 100644
> --- a/tests/qemu-iotests/common.rc
> +++ b/tests/qemu-iotests/common.rc
> @@ -56,6 +56,12 @@ poke_file()

I don’t know how you did it, but something in your workflow broke this
patch.  This should be -56,18 +56,30.

(Note that git accepts this patch without error, but it drops everything
after the first part.  I noticed because your squash-in failed to apply.
 I suppose I might have noticed later when reviewing, because only
peek_file_le() was touched, but who knows.)

>  # peek_file_le 'test.img' 512 2 => 65534
>  peek_file_le()
>  {
> -    # Wrap in echo $() to strip spaces
> -    echo $(od -j"$2" -N"$3" --endian=little -An -vtu"$3" "$1")
> +    local val=0 shift=0 i
> +
> +    # coreutils' od --endian is not portable, so manually assemble bytes.
> +    for i in $(od -j"$2" -N"$3" -An -v -tu1 "$1"); do

“i” is a weird name for something that isn’t an index.

> +        val=$(( val | (i << shift) ))
> +        shift=$((shift + 8))
> +    done
> +    echo $val
>  }
> 

Regarding the broken patch format again: There are no spaces here...

>  # peek_file_be 'test.img' 512 2 => 65279
>  peek_file_be()
>  {
> -    # Wrap in echo $() to strip spaces
> -    echo $(od -j"$2" -N"$3" --endian=big -An -vtu"$3" "$1")
> +    local val=0 i
> +
> +    # coreutils' od --endian is not portable, so manually assemble bytes.
> +    for i in $(od -j"$2" -N"$3" -An -v -tu1 "$1"); do
> +        val=$(( (val << 8) | i ))
> +    done
> +    echo $val
>  }
> 

...and here like there normally would be.

With the patch format fixed, and your proposed to-be-squashed patch
squashed in, there isn’t anything wrong, so:

Reviewed-by: Max Reitz <address@hidden>

But if I’m already about to squash something in, would you allow me to
rename all instances of “i” to e.g. “byte”?

Max

> -# peek_file_raw 'test.img' 512 2 => '\xff\xfe'
> +# peek_file_raw 'test.img' 512 2 => '\xff\xfe'. Do not use if the raw data
> +# is likely to contain \0 or trailing \n.
>  peek_file_raw()
>  {
>      dd if="$1" bs=1 skip="$2" count="$3" status=none
> 


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