Re: [PATCH] tests/testsuite.at: Don't use $as_echo

On 3/13/20 4:27 PM, Zack Weinberg wrote:
> tests/testsuite.at was using the undocumented internal shell variable
> $as_echo to set its own variable $ECHO.  M4sh stopped setting this
> variable in a patch committed to autoconf development trunk in January
> of 2013, which was mostly harmless since there was a fallback setting
> for $ECHO.  As of March 2020, however, merely mentioning $as_echo in
> an m4sh input file will trigger a -Wobsolete warning.
> 
> The fix is to promote the fallback setting to be the default setting
> and not reference $as_echo anymore.  This is safe for the same reason
> it was safe for autoconf to stop setting $as_echo -- 'printf %s\n' is a
> reliable way to do echoing in all of the shells that are worth worrying
> about anymore.
> ---
>   tests/testsuite.at | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/tests/testsuite.at b/tests/testsuite.at
> index d561c2a4..9e33c75a 100644
> --- a/tests/testsuite.at
> +++ b/tests/testsuite.at
> @@ -29,8 +29,7 @@ m4_divert_push([PREPARE_TESTS])dnl
>   : ${AUTOCONF=autoconf}
>   : ${AUTOMAKE=automake}
>   : ${AUTORECONF=autoreconf}
> -test set = "${ECHO+set}" || ECHO=${as_echo-'printf %s\n'}
> -: ${ECHO=$as_echo}
> +: ${ECHO='printf %s\n'}

Side comment: I just realized that:

$ECHO "arg1" "arg2"

is NOT the same as:

echo "arg1" "arg2"

due to use of a newline rather than a space between the arguments.  That 
is, $ECHO is only safe to use with a single argument.  But that fact is 
true regardless of this patch, and I did not bother auditing whether we 
violate that usage pattern anywhere (perhaps we could make $ECHO expand 
to a function call, where the function loudly complains about $# > 1, if 
we wanted to make such an audit easier).

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org