[Boost-build] Directory caching interferes with path.exists/glob when the filesystem is modified during Jamfile parsing

Subject: [Boost-build] Directory caching interferes with path.exists/glob when the filesystem is modified during Jamfile parsing
From: Matthew Chambers (matthew.chambers_at_[hidden])
Date: 2009-09-15 18:14:34

A simple test case:

import common path ;
.TOUCH = [ common.file-touch-command ] ;
echo Before touch ;
if [ path.exists foo ] { echo Foo exists! ; } # should not exist

SHELL "$(.TOUCH) foo" ;

echo After touch ;
if [ path.exists foo ] { echo Foo exists! ; } # should exist

With this code, the last if statement doesn't pass because it's working 
off the cached directory list. If directory caching is desirable during 
or before parsing all the Jamfiles, then one solution might be to use 
system calls to monitor the cached directories and refresh them when a 
modification is detected. Windows has such a call, dunno about other 
platforms. Another solution might be to have a native rule that can 
invalidate the cache for a given directory passed to the rule.

This issue also seems to affect source file binding and scanning.

-Matt