[dpdk-dev] Inter-PMD dependencies when building shared libraries

[Thomas Monjalon]

05/10/2017 14:12, Olivier MATZ:
> On Mon, Oct 02, 2017 at 08:48:29PM +0000, Eads, Gage wrote:
> > I believe I've spotted an issue in the way inter-PMD dependencies are handled when building shared libraries. The depdirs_rule in mk/rte.subdir.mk relies on DEPDIRS-xyz containing the names of subdirectories that xyz depends on. In mk/rte.lib.mk, these DEPDIRS are converted into LDLIBS. This works when the subdirectory names match the library names (i.e. any of the libraries under lib/). However when the dependency is on a PMD, the subdirectory and library names don't match.
[...]
> To solve this, we can either:
> 
> 1- do additional fixes of the "dir name -> lib name" conversion in
>    lib.mk for all this list above, as we are doing for eal or
>    ethdev. This looks feasible, but quite ugly.
> 
> 2- rename all directories to match the libname (ex: drivers/net/null
>    becomes drivers/net/librte_pmd_null). Looks to be a bad idea ;)
> 
> 3- stop to generate the list of libraries from depdirs: DEPDIRS is
>    kept for directory dependency at build, and the list of libraries
>    is advertised in LDLIBS variable, in each Makefile.
> 
> My vote would go for option 3.

We could have several libraries in the same directory.
So I vote for option 4:

4- Replace directory dependencies with library dependencies in makefiles.
   And convert libs to dirs with an autogenerated table.

Note: that's why I don't like recursive makefiles like we have
in the DPDK build system. It forces us to deal with directories
instead of just declaring dependencies on real file targets.