hi all. I want to use dynlink with a statically linked binary.
my dune file looks like
(env (static (flags (:standard -ccopt -static ))))
(executable (name main)
(libraries dynlink)
;(link_flags -linkall) I can add this, but the problem is the same
(modules main) )
(executable (name dyn)
(modules dyn)
(link_flags -linkall)
(modes (native plugin))
(embed_in_plugin_libraries stdlib) )
and this is the error I get :
dune build main.exe --profile static ; \
dune build dyn.cmxs ; \
cd _build/default ; \
./main.exe ; \
ldd main.exe || true ; \
ocamlobjinfo dyn.cmxs ; \
cd -
ocamlopt main.exe
/usr/bin/ld: /home/abate/Projects/repos/tezos/tezos_master/_opam/lib/ocaml/libasmrun.a(unix.n.o): in function `caml_dlopen':
/home/abate/Projects/repos/tezos/tezos_master/_opam/.opam-switch/build/ocaml-base-compiler.4.12.0/runtime/unix.c:271: warning: Using 'dlopen' in statically linked applications requires at runtime the shared libraries from the glibc version used for linking
error loading shared library: Dynlink.Error (Dynlink.Cannot_open_dll "Failure(\"/home/abate/Projects/repos/tezos/test-dynlink/_build/default/dyn.cmxs: undefined symbol: camlStdlib__format__printf_1230\")")
not a dynamic executable
File dyn.cmxs
Name: Dune__exe__Dyn
CRC of implementation: 3f141250177d7b60b987e7f5d99446f3
Globals defined:
Dune__exe__Dyn
Interfaces imported:
82dadcd908dde621b8842c96ba644dc6 Stdlib__uchar
185075aa99b059ad4cae15cb411fcc0c Stdlib__seq
e8696010fc66d4ce9a3bc3f311f6ea20 Stdlib__format
9eaf2b1cd70e33601c152d1ce1bb8be9 Stdlib__buffer
4b04b4eda19aa722df365141895fb347 Stdlib
9fc7c355dbbc8f9dae052e4c2ee0e13d Dune__exe__Dyn
b6c6694955e10001aed267571104a961 CamlinternalFormatBasics
Implementations imported:
41296ac99a85560c95c2f9d56ed27a7d Stdlib__format
there are two problems.
first the warning. Does this mean if I compile the statically linked library on alpine (musl ) i cannot use any dyn linked modules compiled on glibc : this is just a confirmation, then answer seems clear.
second: how do I solve this linking problem with format ?
I’m not sure I follow, but off the bat it seems strange to try to embed the stdlib into the plugin. I would try removing (embed_in_plugin_libraries ...) and (link_flags -linkall) in the rule for the plugin and add back (link_flags -linkall) to the rule for main.exe.
I don’t think the static profile is used in the dynmodules
I get the same problem if I specify explicitely two different profiles dune build main.exe --profile static and `dune build dyn.cmxs --profile dev" .
Building static binaries is very system-specific and I wouldn’t be surprised if by doing so the final executable main.exe ended up stripped (no symbol table) which would make using Dynlink impossible.
You can check this by running nm -g main.exe (NB this is from memory) and check if the symbol camlStdlib__format__printf_1230 is listed.
I just tried this in a standard Ubuntu install and it works. The issue you are having must be related to your use of musl. Linking objects built with different libc’s sure sounds like a long shot.
Sorry, I had tried the wrong thing. I think that the problem is what I mentioned earlier, namely that by building a static executable the binary no longer has a “dynamic symbol table” (this is the table of symbols visible to shared objects which want to link against the binary). To check this, try readelf --dyn-syms main.exe. I think you will find it empty.
it’s indeed empty. So if I manage to populate this table, then symbol problem should disappear ? At the same time I’m not sure if -ccopt -static is compatible with the idea of having dynamic symbols…
