Re: AC_PATH_PROGS_FEATURE_CHECK results in namespace invasion

[Peter Rosin]

On 2014-02-27 02:00, Peter Rosin wrote:
> On 2014-02-27 01:38, Russ Allbery wrote:
>> Peter Rosin <address@hidden> writes:
>>> On 2014-02-27 01:20, Russ Allbery wrote:
>>
>>>> Wouldn't you name the variable FOO_FEATURE?  In other words, I think
>>>> the example in the Autoconf manual is not the best, but the
>>>> functionality you need is there.  I would rewrite the example as:
>>>>
>>>>     AC_CACHE_CHECK([for m4 that supports indir], [ac_cv_path_M4_indir],
>>>>       [AC_PATH_PROGS_FEATURE_CHECK([M4_indir], [m4 gm4],
>>>>           ...
>>>>     AC_SUBST([M4], [$ac_cv_path_M4_indir])
>>
>>> That doesn't work, because then you can't shortcut the test with the
>>> natural M4=/some/gnu/place/m4, you'd be forced to write M4_indir=...
>>> instead. This is even worse than saving the ac_cv_path_FOO variable
>>> during the AC_PATH_PROGS_FEATURE_CHECK macro, since it would be visible
>>> to the end user.
>>
>> Good point.  However, couldn't you just put:
>>
>>     : ${ac_cv_path_M4_indir:=$M4}
>>
>> before the above code?
> 
> Good point. Or put
> 
>       : ${M4_indir:=$M4}
> 
> just before AC_PATH_PROGS_FEATURE_CHECK... Ho humm, which is best? Do I
> want to see (cached) when overriding in the environment? Or not?

I think ": ${M4_indir:=$M4}" is slightly better, because then
M4_indir=/gnu/stuff/m4 beats M4=/crappy/shit/m4 while
ac_cv_path_M4_indir=/goodness/m4 still trumps both of them.

But that's probably of little practical importance...

Cheers,
Peter