Re: Chnaging MAKEFLAGS

[John Graham-Cumming]

On Fri, 2005-01-14 at 14:32, Greg Kilfoyle wrote:
> The manual (section 5.6.3) suggests that I can change the value of
> variable MAKEFLAGS such that the current make file will refer to the new
> setting. I can't get this to work. I have the following Makefile:
> 
> MAKEFLAGS := $(MAKEFLAGS) -Imk
> include util.mk
> $(warning done)
> 
> ...there is a file called util.mk in directory mk, but the include line
> fails:
> 
> guitar:gregk ~ {1558} make
> Makefile:3: util.mk: No such file or directory
> Makefile:5: done

That's not going to work because MAKEFLAGS is used for communication to
sub-makes: i.e. MAKEFLAGS is read when you do $(MAKE) in a rule.  So you
can change MAKEFLAGS in a Makefile and it will affect any $(MAKE) calls
that you make, but it will not affect the current Makefile.

BTW, you should probably use GNU Make's += operator instead of the :=
form in your Makefile.  I would change

MAKEFLAGS := $(MAKEFLAGS) -Imk

to

MAKEFLAGS += -Imk

for two reasons: firstly it's neater and secondly += takes into account
with its LHS is a simply defined or recursively defined variable and
does the right thing without you needing to worry.  Note that += adds a
space before the thing it's appending.

What are you trying to achieve with the dynamic setting of -Imk?

John.
-- 
John Graham-Cumming

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