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RE: how to allow multiple empty commands?


From: Mark Galeck (CW)
Subject: RE: how to allow multiple empty commands?
Date: Thu, 4 Feb 2010 16:44:07 -0800

>What makes you think that make will examine a header file, do the
implicit rule search for it and decide there's no match, and then
later in the same run do the search again?  Have you examined "make
-d" output to see whether that's the case?


Yes indeed with the -d option, I can see that make is remaking foobar multiple 
times, in case like

foobar::;
foobar::;


GNU make manual indicates that there are "multiple ways" to avoid any implicit 
rule search for a target, but I only see one, to have an empty command for that 
target.  What are the others, and are there any that I can use multiple times 
on the same target, without make complaining.  

I had to forget my "solution" of dumping make stderr, because for some reason, 
linker errors were in there (compiler errors and warnings are not).  So now I 
cannot avoid this, I would estimate, 10s of millions of times, make checking 
whether my foobar.h files have any implicit rules and should possibly be 
"remade".  Anybody knows how to avoid it, please let me know.  




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