Re: need help with the Makefile

[John Graham-Cumming]

address@hidden wrote:
> a. should I ask user to pass some env variable such as KVER=2.4 or KVER=2.6 at 
> the make command line and then check the $(KVER) and setup the flags 
> accordingly.

Well that's one way to do it, if you can't do autodetection of the 
version that you are trying to build.

> Also is it possible to check for empty variable and exist with some error msg 
> like following
>
> check_ver:
>         ifeq ($(strip $(KVER)),)
>           @echo "Error: Please set KVER"
>         Endif

That's not going to work because you've got a tab before ifeq and endif 
which means GNU Make is going to pass them to the shell and those are 
internal GNU Make preprocessor commands.

My recommendation is not to do the checking of KVER in a rule (because 
that rule might never get run).  Instead just check KVER in the Makefile 
at the start and using $(error) to output the message.

ifeq ($(strip $(KVER)),)
$(error Please set KVER before running Make)
endif

John.
--
John Graham-Cumming
address@hidden

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