Re: [Xen-devel] fatal error if Flex and Bison is not configured

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Ian Campbell writes ("Re: [Xen-devel] fatal error if Flex and Bison is not 
configured"):
> I wonder if this is to do with timestamp skew or something like that
> cause false reruns of bison? Those would then fail (no bison) which in
> turn would cause make to delete the target.

Timestamp skew could certainly cause this.

Is NFS involved ?  Does the computer you're using have a stable,
synchronised, clock ?  Are you copying working trees about ?  Are you
using a tree actually cloned with hg ?

It's also possible, I guess, that hg takes no special care with
mtimes, in which case just "hg pull" might, if you were unlucky,
update the files in different seconds and in the wrong order.

> Perhaps we need to disable the flex and bison rules unless some magic
> flag is set (by those who are modifying the relevant sources)?

Well, we have configure now.  We could enable those rules iff
(suitably recent[1]) bison and flex were found.

[1] The original reason why we checked these files into the tree was
that shipped versions of Centos and RHEL had truly prehistoric
versions which didn't support making properly reentrant
scanners/parsers.

Ian.

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