Re: [dpdk-dev] [PATCH v3 5/5] net/mlx: fix overlinking with meson and glue dlopen

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

On Tue, Feb 11, 2020 at 02:19:42AM +0100, Thomas Monjalon wrote:
> If ibverbs_link is dlopen, the PMD and application should not
> be linked with ibverbs, but the glue library is.
> Unfortunately the ibverbs dependency was exported in the
> variable ext_deps, so there were overlinking.
> 
> It is fixed by not exporting the dependency in ext_deps,
> and recreating a limited dependency object for cflags only.
> 
> Fixes: 1dd7c7e38c19 ("net/mlx4: support meson build")
> Fixes: 96d7c62a70c7 ("net/mlx5: support meson build")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
> ---
>  drivers/common/mlx5/meson.build | 6 ++++--
>  drivers/net/mlx4/meson.build    | 6 ++++--
>  2 files changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/common/mlx5/meson.build b/drivers/common/mlx5/meson.build
> index 2bb2a83c45..2956fc20e2 100644
> --- a/drivers/common/mlx5/meson.build
> +++ b/drivers/common/mlx5/meson.build
> @@ -30,7 +30,7 @@ foreach libname:libnames
>  	endif
>  	if lib.found()
>  		libs += lib
> -		if not static_ibverbs
> +		if not static_ibverbs and not dlopen_ibverbs
>  			ext_deps += lib
>  		endif
>  	else
> @@ -38,10 +38,12 @@ foreach libname:libnames
>  		reason = 'missing dependency, "' + libname + '"'
>  	endif
>  endforeach
> -if build and static_ibverbs
> +if build and (static_ibverbs or dlopen_ibverbs)
>  	# Build without adding shared libs to Requires.private
>  	ibv_cflags = run_command(pkgconf, '--cflags', 'libibverbs').stdout()
>  	ext_deps += declare_dependency(compile_args: ibv_cflags.split())
> +endif
> +if build and static_ibverbs
>  	# Add static deps ldflags to internal apps and Libs.private
>  	ibv_ldflags = run_command(ldflags_ibverbs_static, check:true).stdout()
>  	ext_deps += declare_dependency(link_args:ibv_ldflags.split())

One small suggestion:
Since out minimum version of meson is 0.47.1, we can use subdir_done()
function. Putting subdir_done() immediately after build=false will simplify
things as you won't need to continually check the build variable in each if
statement.

/Bruce