[PATCH] Use AC_SUBST_FILE to replace @DEPEND@ with contents of .depend

[Michael Forney]

On 2021-06-24, Michael Forney <mforney at mforney.org> wrote:
> On 2021-04-18, Michael Forney <mforney at mforney.org> wrote:
>> AC_SUBST_FILE[0] is similar to AC_SUBST, but instead of replacing
>> a variable with its value, it replaces a variable with the contents
>> of the file named by the value. This is exactly what we want in
>> order to insert the contents of .depend at the end of the Makefile.
>>
>> Using AC_SUBST for this purpose poses some problems if $as_echo
>> involves running an external command (i.e. printf is not built-in),
>> in which case the size of .depend may exceed the operating system's
>> argument size limit. In particular, since autoconf 2.70, $as_echo
>> no longer uses `print -r` on ksh shells[1], causing the following
>> message when creating config.log on Linux with oksh:
>>
>>   ./configure: printf: Argument list too long
>>
>> AC_SUBST_FILE requires the substitution string to be on its own
>> line, so drop the unneeded leading comment (the first line of .depend
>> has a '#' of its own).
>>
>> [0]
>> https://www.gnu.org/software/autoconf/manual/html_node/Setting-Output-Variables.html
>> [1]
>> http://git.savannah.gnu.org/gitweb/?p=autoconf.git;a=commitdiff;h=2b59b6f8a79b8bf77e178ff4e5aa0ede433d39cf;hp=bea5177adc0c924fe7483509a5e38a6d49319fcb
>
> Ping on this patch.

Any concerns with this patch? I thought it would be fairly
uncontroversial since it uses the autoconf macro designed exactly for
this purpose.