[dpdk-dev] [PATCH 0/2] remove use of weak functions from libraries
bruce.richardson at intel.com
Tue May 28 10:06:27 CEST 2019
On Mon, May 27, 2019 at 04:57:15PM -0400, Aaron Conole wrote:
> Bruce Richardson <bruce.richardson at intel.com> writes:
> > On Mon, May 27, 2019 at 04:13:53PM +0200, David Marchand wrote:
> >> Hello,
> >> On Wed, Apr 10, 2019 at 3:45 PM Bruce Richardson
> >> <bruce.richardson at intel.com> wrote:
> >> Weak functions don't work well with static library builds as the
> >> linker
> >> always picks the first version of a function irrespective of whether
> >> it is
> >> weak or not. The solution to this is to use the "whole-archive" flag
> >> when
> >> linking, but this has the nasty side-effect that it causes the
> >> resulting
> >> binary to be larger than it needs to be.
> >> A further problem with this approach of using "whole-archive" is
> >> that one
> >> either needs to link all libraries with this flag or track what
> >> libraries
> >> need it or not - the latter being especially a problem for apps not
> >> using
> >> the DPDK build system itself (i.e. most apps not shipped with DPDK
> >> itself).
> >> For meson builds this information needs to make its way all the way
> >> through
> >> to the pkgconfig file generated - not a trivial undertaking.
> >> Thankfully, though, the use of weak functions is limited to use for
> >> multiple functions within a single library, meaning that when the
> >> lib is
> >> being built, the build system itself can know whether the "weak"
> >> function
> >> is needed or not. This allows us to change the weak function to a
> >> conditionally compiled regular function used in fallback case. This
> >> makes
> >> the need for "whole-archive" flag, and any special linking measures
> >> for the
> >> library, go away.
> >> [This set does not touch the drivers, only the libraries, since
> >> there are
> >> other special linker flags needed for drivers in general, making the
> >> problem less severe for driver .a files.]
> >> Was there something preventing this patchset from getting merged ?
> >> --
> >> David Marchand
> > I believe Aaron Conole had some changes in the same area and was looking to
> > roll these changes into a bigger patchset of his. Aaron, can you please
> > confirm?
> Yes - Sorry the patches are in my queue. Maybe it just makes sense to
> merge these though?
Funnily enough, I've no objections to that :-)
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