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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2012-04-12 at 14:28 +0100, George Dunlap wrote:
> On Thu, Apr 12, 2012 at 12:24 PM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> 
> wrote:
> > On Thu, 2012-04-12 at 12:12 +0100, zhihao wang wrote:
> >> Hi all,
> >>
> >> I try to build xen 4.2( revision number: 25161) on Ubuntu 11.10_amd64,
> >> Mac pro. After running ./configure and make. I got the following fatal
> >> error:
> >>
> >> libxlu_cfg_y.y:22:26: fatal error: libxlu_cfg_l.h: No such file or
> >> directory compilation terminated.
> >>
> >>
> >> So the original libxlu_cfg_l.h is deleted when making, and should be
> >> regenerated but it is not.
> >
> > Actually it should never have been deleted in the first place, unless
> > you have been modifying the flex source.
> >
> > Please can you enumerate the exact steps you took, starting from the
> > initial clone of the repo, which caused the file to be deleted?
> >
> >> I find the path of flex and bison is not set.  When I add the correct
> >> path of flex and bison in tools.mk manually, This error is fixed.
> >
> > Those tools should be optional since the generated files are checked in.
> > However perhaps configure should detect and provide the paths but behave
> > in a non-fatal manner if they aren't available? Roger, what do you
> > think?
> 
> FWIW, I managed to get into a state where I ran into this error too;
> after a sequence of fairly random steps, it went away, and I wasn't
> able to reproduce it again.  I have no idea what I did to get there in
> the first place, nor what I did to fix it.

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.

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

CCing IanJ on the assumption he knows what's going on here..

> Zhihao: I think if you make a clean copy of the repo and run
> ./configure again, the problem will probably go away.

"hg revert <paths>" would probably do the job too.

Ian.



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