Re: [PATCH v2 1/6] perf: build: Setup PKG_CONFIG_LIBDIR for cross compilation

[Leo Yan]

Hi Namhyung,

On 6/22/24 00:18, Namhyung Kim wrote:
> Hello,
>
> On Mon, Jun 10, 2024 at 10:54:28AM +0100, Leo Yan wrote:
> > On recent Linux distros like Ubuntu Noble and Debian Bookworm, the
> > 'pkg-config-aarch64-linux-gnu' package is missing. As a result, the
> > aarch64-linux-gnu-pkg-config command is not available, which causes
> > build failures.
> >
> > When a build passes the environment variables PKG_CONFIG_LIBDIR or
> > PKG_CONFIG_PATH, like a user uses make command or a build system
> > (like Yocto, Buildroot, etc) prepares the variables and passes to the
> > Perf's Makefile, the commit keeps these variables for package
> > configuration. Otherwise, this commit sets the PKG_CONFIG_LIBDIR
> > variable to use the Multiarch libs for the cross compilation.
> >
> > Signed-off-by: Leo Yan <leo.yan@xxxxxxx>
> > ---
> >   tools/build/feature/Makefile | 26 +++++++++++++++++++++++++-
> >   tools/perf/Makefile.perf     | 26 +++++++++++++++++++++++++-
> >   2 files changed, 50 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
> > index ed54cef450f5..084f803093c3 100644
> > --- a/tools/build/feature/Makefile
> > +++ b/tools/build/feature/Makefile
> > @@ -82,7 +82,31 @@ FILES=                                          \
> >
> >   FILES := $(addprefix $(OUTPUT),$(FILES))
> >
> > -PKG_CONFIG ?= $(CROSS_COMPILE)pkg-config
> > +# Some distros provide the command $(CROSS_COMPILE)pkg-config for
> > +# searching packges installed with Multiarch. Use it for cross
> > +# compilation if it is existed.
> > +ifneq (, $(shell which $(CROSS_COMPILE)pkg-config))
> > +  PKG_CONFIG ?= $(CROSS_COMPILE)pkg-config
> > +else
> > +  PKG_CONFIG ?= pkg-config
> > +
> > +  # PKG_CONFIG_PATH or PKG_CONFIG_LIBDIR is required for the cross
> > +  # compilation. If both is not set, try to set the lib paths installed
> > +  # by multiarch.
> > +  ifdef CROSS_COMPILE
> > +    ifeq ($(PKG_CONFIG_LIBDIR)$(PKG_CONFIG_PATH),)
>
> Maybe you want to check PKG_CONFIG_SYSROOT_DIR too.

IIRC, the manual says PKG_CONFIG_SYSROOT_DIR is used alongside
PKG_CONFIG_LIBDIR or PKG_CONFIG_PATH for prepending prefix for
the package paths.

I can add checking PKG_CONFIG_SYSROOT_DIR in the new patch set.

> > +      CROSS_ARCH = $(shell $(CC) -dumpmachine)
> > +      PKG_CONFIG_LIBDIR := /usr/local/$(CROSS_ARCH)/lib/pkgconfig/
> > +      PKG_CONFIG_LIBDIR := $(PKG_CONFIG_LIBDIR):/usr/local/share/pkgconfig/
> > +      PKG_CONFIG_LIBDIR := $(PKG_CONFIG_LIBDIR):/usr/local/lib/$(CROSS_ARCH)/pkgconfig/
> > +      PKG_CONFIG_LIBDIR := $(PKG_CONFIG_LIBDIR):/usr/lib/$(CROSS_ARCH)/pkgconfig/
> > +      PKG_CONFIG_LIBDIR := $(PKG_CONFIG_LIBDIR):/usr/share/pkgconfig/
>
> I'm not sure why this ordering.. don't you want to check
> CROSS_ARCH directories first and then /usr/local/share and
> /usr/share directory?

I mainly refered to the script [1] which is an obselete package
('aarch64-linux-gnu-pkg-config') on old Debian/Ubuntu distros.

Your suggestion makes sense to me. I will change order as:

  PKG_CONFIG_LIBDIR := /usr/local/$(CROSS_ARCH)/lib/pkgconfig/
  PKG_CONFIG_LIBDIR := 
$(PKG_CONFIG_LIBDIR):/usr/local/lib/$(CROSS_ARCH)/pkgconfig/
  PKG_CONFIG_LIBDIR := 
$(PKG_CONFIG_LIBDIR):/usr/lib/$(CROSS_ARCH)/pkgconfig/
  PKG_CONFIG_LIBDIR := $(PKG_CONFIG_LIBDIR):/usr/local/share/pkgconfig/
  PKG_CONFIG_LIBDIR := $(PKG_CONFIG_LIBDIR):/usr/share/pkgconfig/

Thanks,
Leo

[1] https://gist.github.com/doug65536/ea9c52f9a65a655a2fd5cc4997e8443b