RE: makedepends and implicit rule

[sharan basappa]

I am sorry if this caused confusion.

BTW, I was not reporting a bug but was just trying to understand gmake 
(which is what my first
sentence in the mail says)

>   Make has an implicit "%.o : %.c" rule.  Look in the make info file, 
> section
> 10.2 "Catalogue of Implicit Rules".

The question I was asking how make decides to compile even though I dont 
have a rule
of the form
*.o : *.c
The only rule I have is
a : a.o
I believe this rule should force make to invoke linker but make also invokes 
compiler (cc -c -o b.o b.c)

Thanks ...

> From: "Dave Korn" <address@hidden>
> To: "'sharan basappa'" <address@hidden>,<address@hidden>
> Subject: RE: makedepends and implicit rule
> Date: Tue, 30 Jan 2007 16:42:11 -0000
>
> On 30 January 2007 15:50, sharan basappa wrote:
>
> > I am trying to get my make basics right.
> >
> > I have 2 questions about working of make
> >
> > 1) Implicit rules
> >
> > I write a rule like this
> >
> > a : a.o
> >
> > When I execute make, the foll. 2 command execute
> >
> > cc -c -o b.o b.c
> > cc b.o -o b
>
>   If you're reporting a problem or bug, it's a really bad idea to falsify 
> your
> bug report.  Cut and paste the actual output into your email, because if 
> you
> retype it by hand, you'll get it wrong.  It's such an obvious mistake here
> that it didn't do any harm, but if you got a more subtle typo you could 
> waste
> hours of somebody's time trying to sort out a problem that wasn't actually
> what you said it was.
>
> > Thing which is perplexing is that I have not written a fule which has 
> a.o as
> > target, yet make
> > compiles a.c and creates a.o (its a different story that this is what I
> > really wanted make to do)
> >
> > Which implicit rule is making this happen ?
>
>   Make has an implicit "%.o : %.c" rule.  Look in the make info file, 
> section
> 10.2 "Catalogue of Implicit Rules".
>
>
> > 2) makedepend
> >
> > I am trying to use makedepend to create dependancy rules automatically.
> > My make to do that is as follows
> >
> > b : b.o
> >
> > .PHONY : depend
> > depend :
> >       @makedepend -f -b.c > dependancies.d
> >
> > -include dependancies.d
> >
> > Is there a file called dependancies.d created when as a result of 
> executuion
> > of this make file ?
> > I did not find this file in my dir ? Am I doing some mistake ?
>
>   If you just run "make" without any commands, it treats the very first 
> target
> in the makefile as the target to build.  So in your makefile above, you are
> telling it to build target "b".  You haven't told it to build the "depend"
> target, and making it PHONY doesn't make it automatically get built, it 
> just
> means that it will always be assumed to be out-of-date *if* it is the
> prerequisite of a target that you /have/ told build to make.  So you could
> tell make that target "b" requires "depend" as a prerequisite:
>
> b : depend b.o
>
> .PHONY : depend
> depend :
>       @makedepend -f -b.c > dependancies.d
>
> -include dependancies.d
>
> or you could manually run "make depend" instead of just "make".
>
>     cheers,
>       DaveK
> --
> Can't think of a witty .sigline today....

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