Re: [Caml-list] Using OCaml from C

["Stéphane Glondu" <steph@glondu.net>]

Le 10/09/2013 14:21, Tom Ridge a écrit :
> /home/tr61/.opam/4.00.1/lib/core/libcore_stubs.a(unix_stubs.o): In
> function `unix_clock_gettime':
> unix_stubs.c:(.text+0x2776): undefined reference to `clock_gettime'
> 
> I had -lrt after -lpthread, but the error was still reported; when I
> moved -lrt to end of command line things seemed to work; why?

The order of -l options matters, and a library must be put *after*
objects that use its symbols. System linkers have not always been strict
on the ordering, but they started a few years ago. Note that this is
usually the opposite of the order of OCaml objects.

In your case, clock_gettime is provided by -lrt, so -lrt must be after
-lcore_stubs.

> /home/tr61/.opam/4.00.1/lib/core/libcore_stubs.a(unix_stubs.o): In
> function `unix_initgroups':
> unix_stubs.c:(.text+0x3b90): multiple definition of `unix_initgroups'
> /home/tr61/.opam/4.00.1/lib/ocaml/libunix.a(initgroups.o):initgroups.c:(.text+0x0):
> first defined here
> /home/tr61/.opam/4.00.1/lib/core/libcore_stubs.a(unix_stubs.o): In
> function `unix_nice':
> unix_stubs.c:(.text+0x46bc): multiple definition of `unix_nice'
> /home/tr61/.opam/4.00.1/lib/ocaml/libunix.a(nice.o):nice.c:(.text+0x0):
> first defined here
> 
> fixed by adding -Xlinker --allow-multiple-definition to cc options

Is -lunix really needed here? If so, I'd rather put it after
-lcore_stubs. Anyway, this doesn't look right and I would blame Core
here for using the same names as the standard Unix stubs.

> My real question is: what command *should* I be using to compile my
> example? Or is the above more-or-less expected?

Your calls to cp, ar and your use of -custom look suspicious. But it is
difficult to be more helpful without a concrete testcase.


Cheers,

-- 
Stéphane