Original bug ID: 62
Reporter: administrator
Status: closed
Resolution: not a bug
Priority: normal
Severity: minor
Category: ~DO NOT USE (was: OCaml general)

Bug description

Full_Name: Markus Mottl
Version: 2.99+12
OS: Digital Unix 4.0e / Alpha
Submission from: alford.dai.ed.ac.uk (129.215.25.74)

Hello,

there seems to be a strange bug with the linker, which effects
at least ocamlmktop and ocamlopt.opt (seems to be ok with ocamlc.opt

• I have not tried the byte code versions):

The following program (makes use of my PCRE-lib - works with
OCaml 2.99):

open Unix;;
let f () = Pcre.version

behaves strangely when I try to link it (native code) or when I want
to have it interpreted (independent of the specific PCRE-function).

When I link it with ocamlopt.opt, I get the following:

ocamlopt.opt -I {longlibpath} -ccopt -L {longlibpath} -cclib -lpcre pcre.cmxa
-o bla bla.cmx
ld:
Can't open: pcre_intf.o (No such file or directory)

I have not linked in the unix library here (line even longer),
but the result is the same and also then when I leave away
the line containing "open Unix". But...

When I try to interpret it with "mocaml", which I have created
with "ocamlmktop" (also always worked), I get the following
message:

Uncaught exception: Invalid_argument("String.get")

However, if I delete the line containing "open Unix" and
interpret the file with the same toplevel, it works! - It
also runs fine, when the program really does something
interesting with the PCRE-library (as long as I do not
reference the Unix-library somehow)...

Furthermore, when I compile the file with "ocamlc.opt",
the resulting executable works either way (with or without
the "open Unix"-line). Only when I really use a function
from "Unix" do I have to link in the unix-library, which
also works as expected.

So in short: everything (as far as I could see) works fine
with "ocamlc.opt" - but I get an unexpected link error from
ocamlopt.opt and "ocamlmktop" generates a toplevel that
does not behave correctly.

Here, there is another interesting aspect to note:

I normally link in many libraries into "mocaml". When I
leave some of them away, it may be that the above example
immediately works, behaves as before, or issues another
error message like:

File "bla.ml", line 2, characters 11-23:
Unbound value Pcre.version

I have not found out, how the linkage order really
influences behaviour: this seems pretty non-deterministic.
It also seems that the strange behaviour with the toplevel
only appears when I use "open Unix" - not when I leave it
away or open another library (e.g. Str).

That's all I can say so far. I have built my PCRE-library
twice and made sure that its files are where they normally
reside, but the problem did not disappear - maybe
I have overlooked something trivial?

In case you need it for finding the bug (or otherwise ;-),
here the link to my pcre-distribution:

http://miss.wu-wien.ac.at/~mottl/ocaml_sources/intro.html

and take "pcre_ocaml.tar.gz"...

Ah, before I forget: I had to modify a Makefile during the
build process of ocaml (should be independent of upper problem):
the labltk-library (otherlibs/labltk/support) linked with the
option "-label". Since I luckily read the mailing list, I knew
that this should mean "-modern" and changed it appropriately
(the change has obviously not yet made it into the distribution)...

Best regards,
Markus Mottl