Re: about :: sign and % sign problems

[John Graham-Cumming]

Lin George wrote:
> What means "::" (I read related parts from GNU make and still confused)? 
> What is the difference between "::" and ":"?

I doubt that I can do much better than the explanation in the GNU Make 
manual.  The reality is that :: rules are very rarely used or needed in 
Makefiles, you probably don't need to use anything other than normal : 
rules.

Essentially, :: rules allow the same target to be built in different 
ways by different rules.  With : rules there's one rule per target.  :: 
are only used in very odd and special cases.

> Another question, ";" means do nothing, why sometimes we still add some 
> commands after ;? (I mean, if do nothing, we should not add any commands 
> after ";").

No, ; doesn't mean do nothing.  ; means after this semicolon are 
commands that should be executed for this rule.  If there are no 
commands then there are no commands to execute.

John.
--
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