A simple patch.

[Ramón García]

This patch is just to show my experimentation. It causes make to use
the variable .OUT_OF_DATE, evaluated as an expression, for evaluating
when to rebuild a target.

I see one inconvenient with this approach: variables are inherited
from targets to prerequisites. This is useful for setting CFLAGS for a
target to change the compilation of all prerequisites, but for
.OUT_OF_DATE it ensues unconvenient. With the simple Makefile that I
am attaching, it breaks the build, because the .OUT_OF_DATE (which is
always true) propagates to the leaves, and causes them to be out ot
date. I find this propagation surprising. I suggest to add some syntax
to express whether a variable assignment in a target should propagated
downward.

I am also attaching a simple trivial test. You should touch b1 and c1
before trying it. You will see that it does not build correctly with
the patched make for the reason explained.

make.diff
Description: Text Data

Makefile
Description: Binary data