Append value on the command line to a predefined macro in the makefile

[micropentium]

First of all, I should say I apologize if anybody here believe my
topic is tangent...

I have a c file foo.c:

int main(void)
{
#ifdef FOO
printf("FOO!\n");
#endif
#ifdef BAR
printf("BAR!\n");
#endif
return 0;
}

and a Makefile may be like this:
CPPFLAGS=-DFOO
a.out:foo.o
gcc -o $@ $^
%.o:%.c
gcc -c $< ${CPPFLAGS}

if I make it and run a.out (I am on a GNU Make 3.81), the output is
FOO!. If I want to print out BAR! or FOO!BAR!, I could always append -
DBAR onto CPPFLAGS.

So, my question is: what if I want to append -DBAR on the command
line?

I tried: make CPPFLAGS+=-DBAR
But it will completely replace the defined CPPFLAGS in the Makefile.
Obviously, the one defined on the command line has the precedence.

Is this doable through command line arguments to make?

Many thanks!

 

[Flash Gordon]

micropentium wrote:

Is this doable through command line arguments to make?

This is entirely about how to drive make and not about C. Either
comp.unix.programmer or, as it is GNU make you are using a GNU mailing
list, would be a better place to ask. You will find a higher
concentration of people who use make regularly that way.

Also the info pages should prove enlightening.

 

[Nick Keighley]

First of all, I should say I apologize if anybody here believe my
topic is tangent...

don't apologise for posting off-topic stuff, just don't do it!

 

[micropentium]

don't apologise for posting off-topic stuff, just don't do it!

Thank you for the 2 gentlemen above who lead me to the right
direction. I found a thread on gnu make maillist for this:
http://lists.gnu.org/archive/html/help-make/2003-02/msg00001.html

 

[Fred]

First of all, I should say I apologize if anybody here believe my
topic is tangent...

I have a c file foo.c:

int main(void)
{
#ifdef FOO
printf("FOO!\n");
#endif
#ifdef BAR
printf("BAR!\n");
#endif
return 0;

}

and a Makefile may be like this:
CPPFLAGS=-DFOO
a.out:foo.o
        gcc -o $@ $^
%.o:%.c
        gcc -c $< ${CPPFLAGS}

if I make it and run a.out (I am on a GNU Make 3.81), the output is
FOO!. If I want to print out BAR! or FOO!BAR!, I could always append -
DBAR onto CPPFLAGS.

So, my question is: what if I want to append -DBAR on the command
line?

I tried: make CPPFLAGS+=-DBAR
But it will completely replace the defined CPPFLAGS in the Makefile.
Obviously, the one defined on the command line has the precedence.

Is this doable through command line arguments to make?

Many thanks!

In Makefile:
DEFINES = -DFOO $(CPPFLAGS)
gcc -c ${DEFINES} $<

Then command line:
make CPPFLAGS=-DBAR

 

[Tom St Denis]

I tried: make CPPFLAGS+=-DBAR

Learn to use bash [or your shell] and make.

Make takes environment variables as variables internally. In bash if
you wanted two things in a variable just quote it

CFLAGS="-DBAR -DFOO" make

Also in gmake [GNU make] the default for .c files is $(CC) with $
(CFLAGS) as the flags. So you don't need to reference it in your
makefile.

Tom

 

[micropentium]

I tried: make CPPFLAGS+=-DBAR

Learn to use bash [or your shell] and make.

Make takes environment variables as variables internally. In bash if
you wanted two things in a variable just quote it

CFLAGS="-DBAR -DFOO" make

Also in gmake [GNU make] the default for .c files is $(CC) with $
(CFLAGS) as the flags. So you don't need to reference it in your
makefile.

Tom

Hi Tom,

In order to make 'CFLAGS="-DBAR -DFOO" make' work under GNU make, you
have to explicitly give the -e flag to ask Make to import env
variables.

 

[Tom St Denis]

Learn to use bash [or your shell] and make.

Make takes environment variables as variables internally.  In bash if
you wanted two things in a variable just quote it

CFLAGS="-DBAR -DFOO" make

Also in gmake [GNU make] the default for .c files is $(CC) with $
(CFLAGS) as the flags.  So you don't need to reference it in your
makefile.

Tom

Hi Tom,

In order to make 'CFLAGS="-DBAR -DFOO" make'  work under GNU make, you
have to explicitly give the -e flag to ask Make to import env
variables.

No, you don't. I use make every day of my life practically...

CFLAGS="blah" make target

works fine. Some platforms have non-gnu "make" try issuing "gmake"
there.

Tom

 

[micropentium]

I tried: make CPPFLAGS+=-DBAR
Learn to use bash [or your shell] and make.
Make takes environment variables as variables internally. In bash if
you wanted two things in a variable just quote it
CFLAGS="-DBAR -DFOO" make
Also in gmake [GNU make] the default for .c files is $(CC) with $
(CFLAGS) as the flags. So you don't need to reference it in your
makefile.
Tom

Hi Tom,

In order to make 'CFLAGS="-DBAR -DFOO" make' work under GNU make, you
have to explicitly give the -e flag to ask Make to import env
variables.

No, you don't. I use make every day of my life practically...

CFLAGS="blah" make target

works fine. Some platforms have non-gnu "make" try issuing "gmake"
there.

Tom

Hi Tom,

No offense, I completely trust your profession. Let me put it this way
(correct me if I am wrong):

CFLAGS="-DBAR -DFOO" make will set CFLAGS to "-DBAR -DFOO" only if
there is no definition for CFLAGS in makefile. Otherwise, the value
assigned to CFLAGS through env will be overridden by the value defined
in the makefile. However -e flag could reverse this. Again, this is
just based upon my observation on a GNU Make 3.81 for x86_64-redhat-
linux-gnu

Regards