[Buildroot] [PATCH] libselinux: set PREFIX to generate proper .pc file

[Marcus Folkesson <marcus.folkesson@gmail.com>]

Hi Thomas,

On Sun, Jan 07, 2018 at 05:34:27PM +0100, Thomas Petazzoni wrote:
> Hello,
> 
> On Sun, 7 Jan 2018 17:24:34 +0100, Marcus Folkesson wrote:
> 
> > > How can this work without passing PREFIX=/usr also at install time ?
> > > (Same question for libsemanage and libsepol).  
> > 
> > If not PREFIX is passed, it get the value of $(DESTDIR)/usr, which I
> > think is correct?
> 
> No, in the standard semantic of DESTDIR and PREFIX:
> 
>  - PREFIX should be /usr, and DESTDIR $(TARGET_DIR) or $(STAGING_DIR)
>    for target installation
> 
>  - PREFIX should be $(HOST_DIR) for host installation, DESTDIR is not
>    used
> 
> PREFIX is where the software is going to be executed from. So the
> software is going to be executed from /usr for target software, from
> $(HOST_DIR) for host software. PREFIX potentially has an effect on the
> stuff being built: PREFIX might end up being hardcoded into the
> binaries being compiled.
> 
> DESTDIR is used to divert the installation. It is only meaningful
> during installation. It has no effect on the stuff being built: DESTDIR
> is never going to be hardcoded in a binary.
> 

You are right.

> > If PREFIX=/usr at install time, it tries to install on the host
> > system.
> 
> That's bogus.

Just to make clear - *this* package will try to install on the host
system.

> 
> > I guess autotools would have done a better job with DESTDIR and PREFIX.
> 
> Yes.
> 
> > What I can tell, the libselinux.pc is the only target that make use of
> > PREFIX during compile time.
> > 
> > But maybe I should set PREFIX explicitly to $(XXXXX_DIR)/usr during
> > installation just for clarity?
> 
> In the standard (autotools) semantic of PREFIX,
> PREFIX=$(TARGET_DIR)/usr is wrong, see above.
> 
> > From libselinux/src/Makefile:
> > PREFIX ?= $(DESTDIR)/usr
> 
> Yes that's just plain wrong.
> 
> So, two options:
> 
>  - We fix libselinux Makefile to have a more standard DESTDIR/PREFIX
>    usage.

I think we should go for this one in the long run.
I will try to come up with something and get it upstreams for the
selinux project.

Should we keep libselinux Makefile as-is in meanwhile or add patches?

I can take responsibility for the packages being fixed when it is
upstreams.

> 
>  - We keep libselinux Makefile as-is, but we had some comments in
>    libselinux.mk that explain the weird PREFIX/DESTDIR usage.

> 
> Thanks!
> 
> Thomas
> -- 
> Thomas Petazzoni, CTO, Free Electrons
> Embedded Linux and Kernel engineering
> http://free-electrons.com


Best regards
Marcus Folkesson