[Caml-list] OASIS: linking with C library fails

[Caml-list] OASIS: linking with C library fails

[Marek Kubica]

Hi,

I have got this simple example where I try to call a C funtion from
libarchive (yes, I am aware of ocaml-archive):

https://gist.github.com/c52d47cff10e4fe8af33

launcher.ml includes Archive.ml which wraps the C file Archive_stubs.c
which calls libarchive.

Unfortunately, I get an error when I try to build it, it boils down to
this:

src/launch.o: In function `camlLaunch__entry':
/home/marek/ostreamer/_build/src/launch.ml:3: undefined reference to
`ost_version_number'
src/Archive.o: In function `camlArchive':
(.data+0x10): undefined reference to `ost_version_number'
collect2: error: ld returned 1 exit status
File "caml_startup", line 1:
Error: Error during linking
Command exited with code 2.

You can see the complete output (after ocaml setup.ml -clean) in the
Gist. Now I wonder how to fix it? From what I see, Archive_stubs.c gets
compiled to an .o file properly but linking fails as it doesn't seem to
get linked to the library. What am I missing?

regards,
Marek

Re: [Caml-list] OASIS: linking with C library fails

[Marek Kubica]

On Wed, 19 Dec 2012 20:27:28 +0100
Marek Kubica <marek@xivilization.net> wrote:

> You can see the complete output (after ocaml setup.ml -clean) in the
> Gist. Now I wonder how to fix it? From what I see, Archive_stubs.c
> gets compiled to an .o file properly but linking fails as it doesn't
> seem to get linked to the library. What am I missing?

Alright, I figured it out thanks to adrien @ #ocaml: I don't have a
dependency on ost, so it never links the stuff together.

So I stared at ocaml-archive's _oasis file for a bit and figured I try
adding a 

BuildDepends: ost

line in the executable declaration. Lo and behold, it works!

So uhm, thanks for listening :)

regards,
Marek