[Scons-users] timing issues and protecting from them

[Bill Deegan]

Seems like this would need a special --paranoid flag.
I'm not sure there's a foolproof way to do this even?

For example this sequence of events if scons was to record the md5 of the
generated file.
scons creates file.
User modified file.
scons reads md5 of file as it's "Golden" record of file and uses it going
forward.


On Tue, Dec 8, 2015 at 3:50 PM, Tom Tanner <trtanner at btinternet.com> wrote:

> I've had an issue recently where someone updated a file while it was being
> used for a build (please, don't ask).
>
> This results in an interesting sort of race hazard where the generated
> file information in the database says it's made from one version of a file,
> but it's actually made from another. If this happens it tends to result in
> errors, especially if that generated file ends up in your cache.
>
> So it seemed to me that once you'd built a target it'd be a good idea to
> at least check all the prerequisites of the target hadn't changed their
> timestamp (as that would presumably be rather quicker than checking the md5
> and just as effective) and generate an error.
>
> But I'm not sure where the best place to  do that check would be or how to
> list all the prerequisites of a node. Has anyone come across this or know
> where I might want to start looking.
>
> Cheers
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