Re: [dpdk-dev] [PATCH] mk: fix acl library static linking

[Thomas Monjalon <thomas.monjalon@6wind.com>]

2016-06-30 15:02, Sergio Gonzalez Monroy:
> On 30/06/2016 13:44, Thomas Monjalon wrote:
> > 2016-06-30 13:04, Sergio Gonzalez Monroy:
> >> On 30/06/2016 12:38, Thomas Monjalon wrote:
> >>> Does it need to be commented in rte.app.mk?
> >>> The other libs are in whole-archive to support dlopen of drivers.
> >>> But the problem here is not because of a driver use.
> >> There seem to be a bunch of libraries under --whole-archive scope that
> >> are not
> >> PMDs, ie. cfgfile, cmdline...
> >>
> >> What is the criteria?
> > The criteria is a bit vague. We must try to include only libs which can
> > be used by a driver.
> > cmdline should probably not be there.
> > Does it make sense to use cfgfile in a driver? maybe yes.
> 
> So as it is, ACL autotest is broken when building static libs 
> (non-combined).

I think the --whole-archive option must be set specifically for ACL
with a comment explaining it is required because of weak functions:

# librte_acl needs --whole-archive because of weak functions
_LDLIBS-$(CONFIG_RTE_LIBRTE_ACL) += --whole-archive -lrte_acl --no-whole-archive

> For combined libs we usually wrap libdpdk.a with --whole-archive, thus it is
> not an issue.
> 
> Just thinking a bit more about the 'dlopen of drivers' case you 
> mentioned before,
> shouldn't the driver have proper dependencies and therefore need shared 
> DPDK libraries?

It is possible to build a .so, without any DT_NEEDED entries, which will
find the required symbols in the static linked binary.

> What does happen if binary/app and driver are built against different 
> library versions?

Bad things :)

> Where does it say that we do support this use case?

It is maybe not written. But I know it is used by people wanting to load
some PMD.so on demand while having the rest statically compiled.
I agree it needs to be documented and probably better managed and tested.