[Scons-users] timing issues and protecting from them

[Tom Tanner]

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