I'm looking at integrating this a bit more tightly into Felix: the tools, the
compiler,
and of course provide library stuff.
The idea is simple: a "directory stack" is a stack of directories. Duh!
When you open a file for reading:
open_input(stack, filename)
filename is looked for in the stack, top dow.
When you open a file for writing, you always write in the top of stack
directory.
If you do read + write open, the file is searched as for reading, and if found
but not in top of stack it is copied there, and then that is opened.
The effect is a "poor mans src control". Consider the stack
curdir
home
local-mods
felix-library
Then if you compile some library.flx file, the output stuff goes in curdir.
This is good because felix-library and local-mods are read-only anyhow.
With a bit of sex thrown in, you could also recognize filename.patch files
that shadowed a filename file, and generate a patched file "on the fly".
The problem this stuff is meant to solve is this: at present, Felix decides
to write *.cpp etc files right next to the *.flx file. It's supposed to do that!
Unfortunately that won't work for read-only directories.
Also whilst lookup paths provide shadowing on read, writes still go
either in some fixed place or next to the shadow file.. which can still
be read only.
Stacks also solve another problem. Consider directory
felix/lib/std/*.flx
files. We could share std/*.flx except that there are
dependencies on
felix/lib/plat/*.flx
which contains generated files. If you wanted to share the standard library
globally, that's no good.
Directory stacks solve that problem too. The stack is just a path on a directory
tree, with branches for each config. In that case, there's actually a fixed
algorithm for specifying the stack, which is cool .. like I said, it's the path
on the tree so you could have this stack:
share/unix/linux/x86_64/gcc/4.2
share/unix/linux/x86_64/gcc
share/unix/linux/x86_64
share/lunix/linux
share/unix
share
specified by a single pathname.
--
john skaller
[email protected]
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