[Haskell-cafe] Partial statical linking

[Jason Dusek]

2012/9/19 Brandon Allbery <allbery.b at gmail.com>:
> On Wed, Sep 19, 2012 at 7:06 AM, Jason Dusek <jason.dusek at gmail.com> wrote:
>> What I attempted was building a binary with only some C libraries
>> statically linked, with this command line:
>>
>>   # Build https://github.com/erudify/sssp on Ubunut 12.04
>>   ghc -outputdir ./tmp -v --make -O2 sssp.hs -o sssp.ubuntu \
>>     /usr/lib/x86_64-linux-gnu/libffi.a \
>>     /usr/lib/x86_64-linux-gnu/libgmp.a \
>>     /usr/lib/x86_64-linux-gnu/libz.a
>>
>> However, this really made no difference. Running `ldd' on the
>> resulting binary reveals that libz and friends are still
>> dynamically linked:
>
> On Linux you probably need -optl--whole-archive for this to do anything;
> alternately, you would need to get the final ld command line out of ghc and
> insert the above libraries into it *after* the package .a files.
>
> Putting them before the packages (including the GHC runtime) that need them,
> as will happen by default, will cause them to be ignored because they
> contain no required symbols *at that point* in the link.  --whole-archive
> tells to blindly link the whole static archive in instead of ignoring it.

Hi Brandon,

This turned out to be the right ticket. The full command line is
like this:

  ghc -outputdir ./tmp --make -O2 sssp.hs -o sssp.ubuntu \
    -optl-Wl,--whole-archive \
      /usr/lib/x86_64-linux-gnu/libffi.a \
      /usr/lib/x86_64-linux-gnu/libgmp.a \
      /usr/lib/x86_64-linux-gnu/libz.a \
    -optl-Wl,--no-whole-archive

Without the --no-whole-archive at the end, I get errors like:

  (.text+0x880): multiple definition of `__morestack_unblock_signals'
  /usr/lib/gcc/x86_64-linux-gnu/4.6/libgcc.a(generic-morestack.o):(.text+0x880):
first defined here
  /usr/lib/gcc/x86_64-linux-gnu/4.6/libgcc.a(generic-morestack.o): In
function `__morestack_allocate_stack_space':

I am not sure why that happens -- libgcc.a wasn't explicitly
asked for; but it stands to reason that one shouldn't specify
--whole-archive for everything GHC links, just the archives of
interest. Life is short and art is long.

--
Jason Dusek
pgp // solidsnack // C1EBC57DC55144F35460C8DF1FD4C6C1FED18A2B