Re: Allow setting variable using += without prior =

[Simon Josefsson]

Akim Demaille <address@hidden> writes:

>>>> "Simon" == Simon Josefsson <address@hidden> writes:
>
>  > Please enlighten me if there is some obvious problem doing that, as
>  > I can't see it.
>
> I was the one to introduce this limitation, and here is the
> rationale.

Thanks for explaining.

> It was at a time where cleaning the distinction between user and
> Automake variables was much needed.  This also implied that precise
> rules had to be defined as to how ownership transfered.  Because I
> know how painful it is to ensure backward compatibility of bad
> decisions, I became very afraid of the possible case where Automake
> 1.x would not define FOO, and then Automake 1.y would.
>
> A user's FOO += foo would then have a completely different result,
> most probably not the one expected.  If you first FOO =, then again
> the result is more predictable.
>
> Note that using += on an Automake variable is usually much safer,
> since that variable is not likely to have its semantics change.

So would it be possible to make automake not fail if the variable is
an Automake variable?  Perhaps that is complicated to implement,
though.

Or turn the error into a warning?

Thanks,
Simon