%% Dan Jacobson <[EMAIL PROTECTED]> writes: dj> TARGETS : NORMAL-PREREQUISITES | ORDER-ONLY-PREREQUISITES
dj> Well, you got me there. Without examples, we have trouble grasping dj> how to utilize what this Info page is talking about. Sometimes features are advanced enough that providing a simple example of when they might be useful is difficult. There is no common build setup where this feature is really needed; it is used in more obscure situations such as when you have a single command that generates lots of output files that are needed by other parts of the build, maybe header files, and the list of output files is not easily determinable, and you can't write any sort of normal prerequisite relationship for the generated code. dj> Obviously the authors must have learned about make from something that dj> we can't find on our Debian system. Probably one must buy a book to dj> find the full story. As you're no doubt aware, all GNU software _AND_ books are released under a public license. If you're not satisfied, you should consider returning them for a refund. dj> Occasionally, however, you have a situation where you want to impose dj> a specific ordering on the rules to be invoked _without_ forcing the dj> target to be updated if one of those rules is executed. In that case, dj> you want to define "order-only" prerequisites. dj> Sounds just like what I need. Let's print the date before and afterwards, dj> a:|date job date dj> date:; dj> job:;echo $@ dj> That doesn't work. Double colons don't help either. Of course not. Make builds each target exactly one time. Once its command script has been invoked, make assumes it's up-to-date. It won't run the command script twice, no matter how many times the target appears in a prerequisites list. On the off chance you're actually interested in this feature, these prerequisites have semantics similar to normal prerequisites: all this says is that all of the order-only prerequisites must be built before the target that depends on them. Unlike normal prerequisites, though, if one of them is updated that does _NOT_ force the target to rebuild. -- ------------------------------------------------------------------------------- Paul D. Smith <[EMAIL PROTECTED]> Find some GNU make tips at: http://www.gnu.org http://make.paulandlesley.org "Please remain calm...I may be mad, but I am a professional." --Mad Scientist _______________________________________________ Bug-make mailing list [EMAIL PROTECTED] http://lists.gnu.org/mailman/listinfo/bug-make
