Re: about :: sign and % sign problems

[Lin George]

Thanks John!

 

 

> 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.

 

What means "the same target to be built in different ways by different rules"? I can not imagine it -- I also can not find samples from GNU make manual of this point. Could you show me an example please?

 

> 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.

 

I think from your above points, it is the same whether or not adding ; -- since whether ; is added or not, the commands after it will be executed (see the below example). Is it useless?

 

example (with ;)

 

Foo:: Goo;

@ls -a

 

example (without ;)
Foo:: Goo

@ls -a

 

 

In above samples, whether or not ; is added, command "ls -a" (without echo) will be executed.

 

 

regards,

George

John Graham-Cumming <address@hidden> wrote:

> 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.
> -- 
> John Graham-Cumming
> address@hidden
>
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