trying to add fPIC as a flag for gcc

mallas · 01-13-2009, 12:33 PM

Hi,

I am installing a program which needs to be compiled as a 64bit package.
I got the following info from http://cblfs.cross-lfs.org/index.php/FFTW

CC="gcc ${BUILD64} -fPIC" CXX="g++ ${BUILD64} -fPIC" \
./configure --prefix=/usr --libdir=/usr/lib64 --enable-shared --enable-threads &&
make

So I want to add -fPIC to the gcc path. I don't know how though. And in the information above, what is ${BUILD64}?

Also, is CC= and CXX= supposed to be 2 separate command lines?

Only thing I know is when I type exactly that line:
CC="gcc ${BUILD64} -fPIC" CXX="g++ ${BUILD64} -fPIC" \

I get the following:
?
BUILD64: Undefined variable.

This might be super-easy? Haven't handled linux systems before...

Thanks /

Magnus

weibullguy · 01-13-2009, 02:41 PM

BUILD64 is a set of CFLAGS and CXXFLAGS that are defined by the user. At a minimum on an x86_64 CLFS system, this will be the -m64 flag. You can define BUILD64 as an environment variable and use the CBLFS commands as written. For example,

Code:

export BUILD64="-m64 -pipe -mtune=athlon64 -O2 &&
CC="gcc ${BUILD64} -fPIC" CXX="g++ ${BUILD64} -fPIC" \
./configure --prefix=/usr --libdir=/usr/lib64 --enable-shared --enable-threads &&
make

The other option is to replace the BUILD64 with your desired flags. For example,

Code:

CC="gcc -m64 -pipe -mtune=athlon64 -O2 -fPIC" CXX="g++ -m64 -pipe -mtune=athlon64 -O2 -fPIC" \
./configure --prefix=/usr --libdir=/usr/lib64 --enable-shared --enable-threads &&
make

If the distro you're using is standards compliant, the --libdir=/usr/lib64 is correct. If you're not using a standards compliant distro, you may want to change or eliminate this configure option.

mallas · 01-14-2009, 03:28 AM

Thanks, I think I understand how to launch it.

When I use those exakt lines:

CC="gcc -m64 -pipe -mtune=athlon64 -O2 -fPIC" CXX="g++ -m64 -pipe -mtune=athlon64 -O2 -fPIC" \
? ./configure --prefix=/usr --libdir=/usr/lib64 --enable-shared --enable-threads &&

I get:

Invalid null command & the configuration never starts!

And I don't know what's wrong?

Best regards /

Magnus

mallas · 01-14-2009, 04:18 AM

Thanks,

I am using an Intel Core 2, can I use 'native' for the -mtune flag?

What are the -m64, -pipe & -02 flags doing?

If I launch the CC= command I get a question mark at the prompt & nothing happens.

If I launch as root, I get a > at the prompt and nothing happens.

Somehow this command is not triggering anything... or does it?

BTW, my makefile looks like this for the cc flags:

CC = cc
CCDEPMODE = depmode=gcc3
CFLAGS = -O3 -fomit-frame-pointer -fno-schedule-insns -fschedule-insns2 -fstrict-aliasing
CPP = cc -E
CPPFLAGS =

ie no CPPFLAGS...

Should these be the same as the CFLAGS?

Magnus

weibullguy · 01-14-2009, 02:36 PM

It is all one command. The backslash (\) is a line continuation character.

Yes you can use native for -mtune. Read the manual if you want to know what the options do.

When you get the >, it means you haven't completed the command. In this case, it is probably a missing " at the beginning or end of the CC or CXX part.

No, just leave the CPPFLAGS alone. Those are for the preprocessor and shouldn't need changed. If they do, you would likely already know what needs to be added.