This is my first post so please excuse any stupidity on my part regarding make.
I have read the make manual and the O'Reilly book but have not yet found clear
answers to a couple of things :
1. Can someone elaborate a little on the algorithm Make uses to determine when
a file is out of date ?
-in the manual and the book, it says the file's modification time
-does this represent the ctime or the mtime ?
-are there any other factors determining whether a file is out of date ?
-I found on a web page somewhere (could have been about non-GNU make)
that file size was also used... is that true ?
2. In the O'Reilly book "C In a Nutshell", in the Chapter "Using Make to Build
C Programs", in the section on Phony Targets, page 527-8, there is a part that
reads...
.PHONY: bin
bin : circle
$(MKDIR) $@
$(CP) $< $@/
$(CHMOD) 600 $@/$<
An old fashioned, slightly less intuitive way of producing the same effect (as
declaring a target .PHONY) is to add another rule for the target with no
prerequisites and no commands :
bin : circle
$(MKDIR) $@
$(CP) $< $@/
$(CHMOD) 600 $@/$<
bin:
The .PHONY target is preferable if only because it is so explicit, but you may
see the other technique in automatically generated dependency rules, for
example.
I was under the impression that the final prerequisite list for a given target
is the concatenation of all the prerequisites listed for that target which can
appear in several rules.
Why doesn't the line "bin:", just add zero additional prerequisites to the list
and do nothing else ?
Why does the "old fashioned" code have the same effect as the .PHONY code ?
Thank You
Richard
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