topic Re: How to Pass Variables to Makefile in Operating System - Linux

How to Pass Variables to Makefile

Chakkarapani — Wed, 19 Mar 2008 06:41:45 GMT

Hi, I want to know how to pass a variable to makefile from the command prompt. And inside the makefile i want to check this variable and do conditional compilation.
In the command prompt when i just call make i starts executing blindly and no variables i passing for this make. But i need an option like to conditionally compile upon users choice.Please tell me how to establish this.

Re: How to Pass Variables to Makefile

VK2COT — Wed, 19 Mar 2008 09:06:01 GMT

Hello,

You did not specify if you are using
GNU make or standard HP-UX.

Several possibilities:

a) For example, in a properly written
Makefile, the variable CFLAGS is included
in each command that runs the C compiler,
so a file myfile.c would be compiled as:

# cc -c $(CFLAGS) myfile.c

Whatever value is set for CFLAGS, it affects
each compilation.

When you run make, you can override it.

For example

# make CFLAGS='-g -O'

b) In HP-UX, there is make(1) flag "-e":

Environment variables override assignments
within Makefiles

c) HP-UX make(1) supports ifdef
test in Makefile. An example:

ifdef UNAME
SYSTEM = $(UNAME)
else
SYSTEM = "UNSUPPORTED"
endif

Cheers,

VK2COT

Re: How to Pass Variables to Makefile

Dennis Handly — Wed, 19 Mar 2008 17:02:21 GMT

>And inside the makefile i want to check this variable and do conditional compilation.

As VK2COT alluded, you can't do this with HP's make, you must use gmake.

>But i need an option like to conditionally compile upon users choice.

You might be able to do this by explicitly mentioning a target. This allows you to build only parts of the makefile.

>VK2COT: c) HP-UX make(1) supports ifdef
test in Makefile.

I'm not sure where you got this but it isn't in the man page.

The only new feature I see is "conditional macro definition" but this probably won't help.

Re: How to Pass Variables to Makefile

Steven Schweda — Wed, 19 Mar 2008 18:09:17 GMT

> I'm not sure where you got this but it
> isn't in the man page.

Nor, apparently, in reality:

dyi # cat makefile
ifdef UNAME
SYSTEM = $(UNAME)
else
SYSTEM = "UNSUPPORTED"
endif

dyi # make
Make: Must be a separator on rules line 2. Stop.

dyi # gmake
gmake: *** No targets. Stop.

dyi # uname -a
HP-UX dyi B.11.31 U ia64 4235313755 unlimited-user license

Re: How to Pass Variables to Makefile

VK2COT — Wed, 19 Mar 2008 21:04:56 GMT

Hello,

Ahh, wrong statement by me (option c) in previous post).

GNU make supports two types of If test, ifdef
and ifeq (and the negative versions ifndef,
ifneq), not the HP-UX native one!

gmake != HP-UX make

Cheers,

VK2COT