Re: [dpdk-dev] [PATCH] avoid libfdt checks adding full paths to pkg-config

[Bruce Richardson <bruce.richardson@intel.com>]

On Wed, Sep 02, 2020 at 01:10:30PM +0200, Christian Ehrhardt wrote:
> The checks for libfdt try dependency() first which would only work if
> a pkg-config would be present but libfdt has none.
> Then it probes for the lib path itself via cc.find_library.
> 
> But later it adds the result of either probe to ext_deps which ends up
> in build and also the resulting pkg-config to contain toolchain versioned
> paths in Libs.private like:
>   /usr/lib/gcc/x86_64-linux-gnu/9/../../../x86_64-linux-gnu/libfdt.so
> which obviously breaks on toolchain updates.
> 
> In general libs used multiple times - ipn3ke + ifpga in this case - are
> checked centrally in config/meson.build so move it there and fix the
> adding of dependencies to not use the full file path.
> 
> The result is libfdt in pkg-config now showing up as:
>   Libs.private: -pthread -lm -ldl -lnuma -lfdt -lpcap
> 
> Signed-off-by: Christian Ehrhardt <christian.ehrhardt@canonical.com>
> Reviewed-by: Luca Boccassi <bluca@debian.org>
> ---
>  config/meson.build             | 9 +++++++++
>  drivers/net/ipn3ke/meson.build | 6 +-----
>  drivers/raw/ifpga/meson.build  | 7 +------
>  3 files changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/config/meson.build b/config/meson.build
> index cff8b33dd2..1c8317e750 100644
> --- a/config/meson.build
> +++ b/config/meson.build
> @@ -150,6 +150,15 @@ if numa_dep.found() and cc.has_header('numaif.h')
>  	dpdk_extra_ldflags += '-lnuma'
>  endif
>  
> +has_libfdt = 0
> +fdt_dep = cc.find_library('libfdt', required: false)
> +if fdt_dep.found() and cc.has_header('fdt.h')
> +	dpdk_conf.set10('RTE_HAS_LIBFDT', true)
> +	has_libfdt = 1
> +	add_project_link_arguments('-lfdt', language: 'c')
> +	dpdk_extra_ldflags += '-lfdt'
> +endif
> +
>  # check for libbsd
>  libbsd = dependency('libbsd', required: false)
>  if libbsd.found()
> diff --git a/drivers/net/ipn3ke/meson.build b/drivers/net/ipn3ke/meson.build
> index ec9cb7daf0..d5000d807c 100644
> --- a/drivers/net/ipn3ke/meson.build
> +++ b/drivers/net/ipn3ke/meson.build
> @@ -9,11 +9,7 @@
>  #  rte_eth_switch_domain_free()
>  #
>  
> -dep = dependency('libfdt', required: false)
> -if not dep.found()
> -	dep = cc.find_library('libfdt', required: false)
> -endif
> -if not dep.found()
> +if has_libfdt == 0

Minor nit, for readability, I'd suggest using "not has_libfdt", but what is
here can work too.

>  	build = false
>  	reason = 'missing dependency, "libfdt"'
>  	subdir_done()
> diff --git a/drivers/raw/ifpga/meson.build b/drivers/raw/ifpga/meson.build
> index 05a1711b5d..da454b1942 100644
> --- a/drivers/raw/ifpga/meson.build
> +++ b/drivers/raw/ifpga/meson.build
> @@ -1,11 +1,7 @@
>  # SPDX-License-Identifier: BSD-3-Clause
>  # Copyright(c) 2018 Intel Corporation
>  
> -dep = dependency('libfdt', required: false)
> -if not dep.found()
> -	dep = cc.find_library('libfdt', required: false)
> -endif
> -if not dep.found()
> +if has_libfdt == 0
>  	build = false
>  	reason = 'missing dependency, "libfdt"'
>  	subdir_done()
> @@ -16,7 +12,6 @@ objs = [base_objs]
>  
>  deps += ['ethdev', 'rawdev', 'pci', 'bus_pci', 'kvargs',
>  	'bus_vdev', 'bus_ifpga', 'net', 'pmd_i40e', 'pmd_ipn3ke']
> -ext_deps += dep
>  
>  sources = files('ifpga_rawdev.c')
>  
> -- 
Reviewed-by: Bruce Richardson <bruce.richardson@intel.com>