Re: [Automake-NG] [PATCH] memoize: expose a serious bug (for GNU make < 3.83)

[Akim Demaille]

Le 15 mai 2012 à 11:21, Stefano Lattarini a écrit :

> This is a follow-up to commit v1.12-217-gd55204f of 2012-05-12,
> "[ng] vars: implement memoization of make variables (new 'am__memoize'
> func)".
> 
> So, apparently, all our workarounds aimed at avoiding the subtle GNU
> make bug affecting variable memoization:
> 
>  <http://lists.gnu.org/archive/html/bug-make/2012-05/msg00013.html>
>  <https://savannah.gnu.org/patch/?7534>
> 
> have not been enough :-(

Bummer :(

It is my understanding that the bug prevents reassigning to a
variable, right?  So maybe the outer variable, instead of trying
to memoize, could use an $(if) to branch either to evaluate-and-store
in *another* variable else to the value of this memo variable.

This should prevent re-assignment, and result is the sole
extra cost of check whether the memo-variable was set.