If you use "redo --old-args", it will switch back to the old
(apenwarr-style) arguments for now, to give you time to update your .do
scripts. This option will go away eventually.
Note: minimal/do doesn't understand the --old-args option. If you're using
minimal/do in your project, keep using the old one until you update your use
of $1/$2, and then update to the new one.
apenwarr-style default.o.do:
$1 foo
$2 .o
$3 whatever.tmp
djb-style default.o.do:
$1 foo.o
$2 foo
$3 whatever.tmp
apenwarr-style foo.o.do:
$1 foo.o
$2 ""
$3 whatever.tmp
djb-style foo.o.do:
$1 foo.o
$2 foo.o (I think?)
$3 whatever.tmp
The previous method, using fcntl byterange locks, was very efficient and
avoided unnecessarily filesystem metadata churn (ie. creating/deleting
inodes). Unfortunately, MacOS X (at least version 10.6.5) apparently has a
race condition in its fcntl locking that makes it unusably unreliable
(http://apenwarr.ca/log/?m=201012#13).
My tests indicate that if you only ever lock a *single* byterange on a file,
the race condition doesn't cause a problem. So let's just use one lockfile
per target. Now "redo -j20 test" passes for me on both MacOS and Linux.
This doesn't measurably affect the speed on Linux, at least, in my tests.
The bad news: it's hard to safely *delete* those lockfiles when we're done
with them, so they tend to accumulate in the .redo dir.
...because it seems my locking isn't very good. It exposes annoying
problems involving rebuilding the same files more than once, screwing up
stamp files with redo -j, and being unnecessarily slow when checking
dependencies. So it's a pretty good test considering how simple it is.
Didn't add it to t/all.do yet, because it would fail.
