[dpdk-dev] [PATCH 0/2] remove use of weak functions from libraries

Aaron Conole aconole at redhat.com
Mon May 27 22:57:15 CEST 2019


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
>>    <[1]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?

> /Bruce


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