bug#11793: AM_MISSING_PROG undocumented

[Stefano Lattarini]

tags 11793 + wishlist
thanks

> On 06/26/2012 11:39 AM, Eric Blake wrote:
>
>> And while looking into how M4 differs from coreutils, I noticed that
>> coreutils uses this via a .m4 file included into its configure.ac:
>>
>>   AM_MISSING_PROG(HELP2MAN, help2man)
>>
>> which is roughly supposed to set $(HELP2MAN) to 'path/to/missing [--run]
>> help2man', depending on the version of automake used, without
>> hard-coding it as M4 had done.  Maybe M4 could use this trick instead of
>> open-coding its use of 'missing --run', but there's a flaw in that plan
>> - AM_MISSING_PROG is an undocumented macro, and I'm trying hard to keep
>> M4 using only documented interfaces.
>>
>
> AM_MISSING_PROG has been around for a while (git log says it was
> introduced in 1997, although the current two-argument version appears to
> date back to commit 9ae48df in Nov 1999), and seems like something
> stable enough to be worth guaranteeing.
>
> A related suggestion might be to have AM_MISSING_PROG do a filter check
> to make sure that the program name being protected by the 'missing'
> script is indeed one of the programs that the missing script knows how
> to handle in the first place; help2man is in that list.
>
But wouldn't that cause a loss in generality extensibility?  After all,
the 'missing' script (at least in its "lightweight" form on the master
branch) is able to detect and report, albeit with less useful advice and
tips, any failure due to a missing or too old tool (the latter assuming
that such tool is smart enough to exit with status 63 when it wants to
flag a version mismatch error).

Regards,
  Stefano