Re: [dpdk-dev] [PATCH] build: add pkg-config validation

[Gregory Etelson <getelson@nvidia.com>]

Hello Thomas,

> -----Original Message-----
> 
> 29/10/2020 10:16, Gregory Etelson:
> > DPDK relies on pkg-config(1) to provide correct parameters for
> > compiler and linker used in application build.
> > Inaccurate build parameters, produced by pkg-config from DPDK .pc
> > files could fail application build or cause unpredicted results during
> > application runtime.
> 
> Actually this is only for static linkage of examples with makefiles.
>

In our case, pkg-config produced wrong output for statically linked
external application.
General case of error in pkg-config output can lead to any kind of build
or execution fault. 
 
> > This patch validates host pkg-config utility and notifies about known
> > issues.
> >
> > Signed-off-by: Gregory Etelson <getelson@nvidia.com>
> > ---
> > --- a/buildtools/pkg-config/meson.build
> > +++ b/buildtools/pkg-config/meson.build
> > +pkgconf = find_program('pkg-config', 'pkgconf', required: false) if
> > +(pkgconf.found())
> > +     cmd = run_command('./pkgconfig-validate.sh', pkgconf.path(),
> > +                        check:false)
> > +     if cmd.returncode() != 0
> > +             version = run_command(pkgconf, '--version')
> > +             warning('invalid pkg-config version @0@'.format(
> > +                     version.stdout().strip()))
> > +     endif
> > +endif
> 
> Should we restrict this warning to the example makefiles?
>

If DPDK build infrastructure detects wrong pkg-config, it must
notify all applications, internal and external, about the
potential build fault.
 
> 
> > --- /dev/null
> > +++ b/buildtools/pkg-config/pkgconfig-validate.sh
> > @@ -0,0 +1,38 @@
> > +#! /bin/sh
> > +# SPDX-License-Identifier: BSD-3-Clause
> > +
> > +if [ "$#" -ne 1 ]; then
> > +     echo "$0: no pkg-config parameter"
> > +     exit 1
> > +fi
> 
> The default pkg-config from path could considered.
> 

Host can use ether pkg-config or pkgconf utility for
build configuration. The script let the meson build
system to query host what exact utility is used.
Meson passes the query result to the validation script. 

> > +
> > +ret=0
> > +PKGCONF="$1"
> 
> PKGCONF=${1:-pkg-config}
> 

Please see above.

> > +
> > +# take the first result only
> > +pc_file=$(find "$MESON_BUILD_ROOT" -type f -name 'libdpdk.pc' -print
> > +-quit)
> 
> It does not look in PKG_CONFIG_PATH.
>

Meson stores libdpdk.pc template under MESON_BUILD_ROOT. That template has enough
information to run validation queries.
 
> > +if [ ! -f "$pc_file" ]; then
> > +     echo "$0: cannot locate libdpdk.pc"
> > +     exit 1
> > +fi
> > +
> > +pc_dir=$(dirname "$pc_file")
> > +__pkg_config_path="$PKG_CONFIG_PATH"
> > +PKG_CONFIG_PATH="${PKG_CONFIG_PATH}:$pc_dir"
> > +export PKG_CONFIG_PATH
> > +
> > +# Statically linked private DPDK objects of form # -l:file.a must be
> > +positionned between --whole-archive … --no-whole-archive # linker
> > +parameters.
> > +# Old pkg-config versions misplace --no-whole-archive parameter and
> > +put it # next to --whole-archive.
> > +"$PKGCONF" --libs --static libdpdk | \ grep -q
> > +'whole-archive.*l:lib.*no-whole-archive'
> > +if test "$?" -ne 0 ; then
> > +     echo "WARNING: invalid pkg-config"
> > +     ret=1
> > +fi
> > +
> > +# restore PKG_CONFIG_PATH
> > +export PKG_CONFIG_PATH="$__pkg_config_path"
> 
> Instead of restoring, you could just set the variable on the command line
> calling PKGCONF.

Not sure I understand what did mean here.

> 
> > +exit $ret
> 
> 
> > --- a/doc/guides/linux_gsg/sys_reqs.rst
> > +++ b/doc/guides/linux_gsg/sys_reqs.rst
> > +**Known Issues:**
> > +
> > +*   pkg-config v0.27 supplied with RHEL-7 does not process correctly
> libdpdk.pc Libs.private section.
> 
> Is it only the RHEL version or all 0.27 packages?
> 
> Is it enough to warn on issue, or do we prefer recommend a minimal
> version?
> 

We can both warn about pkg-config versions with known issues and validate
host configuration utility during run-time.