4.2 Make - Bug in special macro '$?' with double colons ??

[John M Sellens]

(I wouldn't be suprised if this was present in ALL makes... )

In 4.2bsd make, there seems to be a minor bug in the processing of
makefiles with double colon definition lines.  (The single colon
case works as you would expect - seems to be treated like one big
definition line).  None of the files referred to in the makefile
exist.

The special macro '$?' gets expanded in different ways depending on
the order of the items in the makefile.  It seems that if a double
colon definition does not have any commands, it is treated as part
of the next definition (at least for purposes of determining '$?').

Repeatable as shown below.  My question:  Is this a bug or a feature??
I don't have a fix - to my mind, this is too obscure to really be worth
the trouble.  I only stumbled on it because I am trying to reproduce
the behaviour of make on a PC and I wasn't sure how it was supposed to
react.


	cat Makefile
		all:: one
		        echo ONE $@
		        echo $?
		all:: two
		#       echo TWO $@
		#       echo $?
		all:: three
		        echo THREE $@
		        echo $?
		one: two
		        echo $@
		two:
		        echo $@
		three:
		        echo $@
	make -n -f twoNotDefined  /* # comments there */
		echo two
		echo one
		echo ONE all
		echo one
		echo three
		echo THREE all
		echo two three	<== Notice that two is here, but one is not.
				<== But if you move the line containing
				<== 'all:: two' to after the group that starts
				<== 'all:: three', two no longer shows up on
				<== this line.
	make -n -f twoDefined	/* #'s removed */
		echo two
		echo one
		echo ONE all
		echo one
		echo TWO all
		echo two
		echo three
		echo THREE all
		echo three	<== two is not here!!


John M Sellens
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