Re: [gentoo-dev] [PATCH] systemd.eclass: remove SYSROOT from pkg-config output

[James Le Cuirot <chewi@gentoo.org>]

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On Sun, 3 Jan 2021 12:52:08 +0000
James Le Cuirot <chewi@gentoo.org> wrote:

> On Sat,  2 Jan 2021 20:09:04 -0500
> Mike Gilbert <floppym@gentoo.org> wrote:
> 
> > When cross-compiling, users will typically have
> > PKG_CONFIG_SYSROOT=${SYSROOT} defined via pkg-config wrapper.
> > 
> > When PKG_CONFIG_SYSROOT is set, all paths included in pkg-config
> > output get prefixed with this value.
> > 
> > Signed-off-by: Mike Gilbert <floppym@gentoo.org>
> > ---
> > 
> > This patch has already been pushed, but I figured I would send it for
> > review in case someone else can think of a failure case, or has a better
> > solution.
> > 
> >  eclass/systemd.eclass | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/eclass/systemd.eclass b/eclass/systemd.eclass
> > index 81065a0af79a..f6d1fa2d92d6 100644
> > --- a/eclass/systemd.eclass
> > +++ b/eclass/systemd.eclass
> > @@ -50,6 +50,7 @@ _systemd_get_dir() {
> >  
> >  	if $(tc-getPKG_CONFIG) --exists systemd; then
> >  		d=$($(tc-getPKG_CONFIG) --variable="${variable}" systemd) || die
> > +		d=${d#${SYSROOT}}
> >  		d=${d#${EPREFIX}}
> >  	else
> >  		d=${fallback}  
> 
> I was going to say this is not the best approach as it would be better
> to tell pkg-config to not add the SYSROOT in the first place. I now
> realise we have shot ourselves in the foot with cross-pkg-config as it
> uses SYSROOT to set both PKG_CONFIG_SYSROOT_DIR to control the output
> and PKG_CONFIG_LIBDIR to find the .pc files in the first place. I have
> had prefix-related fixes for cross-pkg-config lined up for over a year
> but unfortunately they do not address this. Trying to accommodate this
> use case would probably just make it more confusing though so maybe
> your approach is best after all.
> 
> The EPREFIX line is (sometimes) wrong in EAPI 7 though and the same goes
> for udev.eclass. It took a while to get this agreed and corrected in
> PMS but if SYSROOT points to / then the effective prefix is BROOT, not
> EPREFIX; they may not be the same. If you just strip ESYSROOT then
> it will always do the right thing but you'll need this fall back for
> older EAPIs. I'm not sure why you didn't do it in one line? I forget if
> EPREFIX is normalised to be / rather thank blank.
> 
> d=${d#${SYSROOT%/}/${EPREFIX#/}}

Had another minute to think. EPREFIX always strips the trailing slash
so it would be blank.

d=${d#${SYSROOT%/}${EPREFIX}}

-- 
James Le Cuirot (chewi)
Gentoo Linux Developer

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