bug#25358: Cross Compiling fails because of help2man

[Jim Meyering]

On Fri, Jan 6, 2017 at 1:44 AM, Assaf Gordon <address@hidden> wrote:
> Hello Jim and all,
>
>> On Jan 5, 2017, at 11:41, Jim Meyering <address@hidden> wrote:
>>
>>> 1. make 'doc/sed.1' depend on 'sed/sed.c' and 'doc/sed.x'
>> I'm pretty sure we must retain the dependency, at least when not
>> cross-compiling. If we were to attempt to remove that dependency, I
>> believe that would leave a race condition where help2man may attempt
>> to run the binary before it is built.
>
> GNU Make has a good solution for it with its "order-only-prerequisites"
> (which ensure proper order but ignore timestamp of the dependency):
>
>  https://www.gnu.org/software/make/manual/html_node/Prerequisite-Types.html
>
> Too bad it's not portable...

Indeed.

>>> 2. make the building of 'doc/sed.1' conditional, depending on wether
>>>   it is being built from '.git' (then regenerate it)
>>
>> Even when building from a tarball, we should leave as many build rules
>> as we can.
>
> We do already distribute 'doc/sed.1' in the tarball, and currently always 
> rebuild it,
> I wonder if it's worth making an exception in this case?

I don't feel strongly about this either way. You're welcome to make the call.

> For example in coreutils I think man pages are skipped if there's no perl. 
> Doing the same in sed will allow building it on system without perl (BTW this 
> was the cause for bug #25367 - it was a system with non-working perl).
>
> If we do go with only skipping for cross-compilation,
> does this suffice for 'configure.ac' ?
>
>     AM_CONDITIONAL([CROSS_COMPILING], [test "$cross_compiling" = yes])

Since that's all coreutils does, I presume it will work for us.

> In that case, perhaps it's worth adding a test for perl and skipping if it 
> doesn't exist ?
>
> I'm expecting more system will ship without perl as time goes by...

This seems worthwhile.