[Caml-list] Errors in installing 'lwt'

[Caml-list] Errors in installing 'lwt'

[Helmut Brandl]

Hello,

I am trying to install 'js_of_ocaml' with 'opam' and run into some 
problems. It seems that the ocaml compile cannot compile the 'lwt' package.

$opam list
Installed packages for system:
base-unix           base  Unix library distributed with the OCaml compiler
camlp4     4.02.0+system  Camlp4 is a system for writing extensible 
parsers for programming languages
cmdliner           0.9.5  Declarative definition of command line 
interfaces for OCaml
menhir          20140422  LR(1) parser generator
ocamlfind          1.5.3  A library manager for OCaml
ppx_tools         0.99.1  Tools for authors of ppx rewriters and other 
syntactic tools

opam install js_of_ocaml
The following actions will be performed:
  - install lwt.2.4.6 [required by js_of_ocaml]
  - install js_of_ocaml.2.5
2 to install | 0 to reinstall | 0 to upgrade | 0 to downgrade | 0 to remove
Do you want to continue ? [Y/n]

=-=-= Installing lwt.2.4.6 =-=-=
Building lwt.2.4.6:
   ./configure --prefix /home/helmut/.opam/system --disable-libev 
--disable-react --disable-ssl --enable-unix --enable-extra 
--disable-preemptive --disable-glib --enable-ppx
   make build
   make install
[ERROR] The compilation of lwt.2.4.6 failed.
Removing lwt.2.4.6.
   ocamlfind remove lwt

[ERROR] Due to some errors while processing lwt.2.4.6, the following 
actions will NOT proceed:
  - install js_of_ocaml.2.5

===== ERROR while installing lwt.2.4.6 =====
# opam-version 1.1.1
# os           linux
# command      ./configure --prefix /home/helmut/.opam/system 
--disable-libev --disable-react --disable-ssl --enable-unix 
--enable-extra --disable-preemptive --disable-glib --enable-ppx
# path         /home/helmut/.opam/system/build/lwt.2.4.6
# compiler     system (4.02.0)
# exit-code    1
# env-file /home/helmut/.opam/system/build/lwt.2.4.6/lwt-25223-ffb3fd.env
# stdout-file /home/helmut/.opam/system/build/lwt.2.4.6/lwt-25223-ffb3fd.out
# stderr-file /home/helmut/.opam/system/build/lwt.2.4.6/lwt-25223-ffb3fd.err
### stderr ###
# ...[truncated]
# W: Failure("Command ''/home/helmut/.opam/system/bin/ocamlfind' query 
-format %d camlp4 > '/tmp/oasis-c39eab.txt'' terminated with error code 2")
# ocamlfind: Package `camlp4' not found
# W: Failure("Command ''/home/helmut/.opam/system/bin/ocamlfind' query 
-format %d camlp4 > '/tmp/oasis-5e24a6.txt'' terminated with error code 2")
# ocamlfind: Package `camlp4.quotations.o' not found
# W: Failure("Command ''/home/helmut/.opam/system/bin/ocamlfind' query 
-format %d camlp4.quotations.o > '/tmp/oasis-f94904.txt'' terminated 
with error code 2")
# E: Cannot find buildable internal library 'lwt-preemptive' when 
checking build depends
# E: Cannot find findlib package camlp4
# E: Cannot find findlib package camlp4.extend
# E: Cannot find findlib package camlp4.quotations.o
# E: Failure("4 configuration errors")

'opam install js_of_ocaml' failed.


Can anybody help (or if this list is not the right location to ask can 
you redirect me)?

Thanks in advance
Helmut

Re: [Caml-list] Errors in installing 'lwt'

[Török Edwin]

On 10/20/2014 04:59 PM, Helmut Brandl wrote:
> Hello,
> 
> I am trying to install 'js_of_ocaml' with 'opam' and run into some problems. It seems that the ocaml compile cannot compile the 'lwt' package.
> 
> $opam list
> Installed packages for system:
> base-unix           base  Unix library distributed with the OCaml compiler
> camlp4     4.02.0+system  Camlp4 is a system for writing extensible parsers for programming languages

Which Linux distribution are you using, and where did you get the packages from?
Do you have both the camlp4 executable and the camlp4 libraries installed (in case they are in separate packages)?


> # W: Failure("Command ''/home/helmut/.opam/system/bin/ocamlfind' query -format %d camlp4 > '/tmp/oasis-c39eab.txt'' terminated with error code 2")
> # ocamlfind: Package `camlp4' not found
> # W: Failure("Command ''/home/helmut/.opam/system/bin/ocamlfind' query -format %d camlp4 > '/tmp/oasis-5e24a6.txt'' terminated with error code 2")
> # ocamlfind: Package `camlp4.quotations.o' not found
> # W: Failure("Command ''/home/helmut/.opam/system/bin/ocamlfind' query -format %d camlp4.quotations.o > '/tmp/oasis-f94904.txt'' terminated with error code 2")
> # E: Cannot find buildable internal library 'lwt-preemptive' when checking build depends
> # E: Cannot find findlib package camlp4
> # E: Cannot find findlib package camlp4.extend
> # E: Cannot find findlib package camlp4.quotations.o

What is the output of:
ocamlfind list|grep camlp4

Did you install ocamlfind before or after you installed camlp4?

Best regards,
--Edwin

Re: [Caml-list] Errors in installing 'lwt'

[helmut.brandl]

I don't know which one I installed first.

The output of 'ocamlfind list | grep camlp4' is empty. 'camlp4' is not in the
list. However opam installed it successfully.

I am working on linux distributed by archlinux.

Re: [Caml-list] Errors in installing 'lwt'

[Török Edwin]

On 10/20/2014 06:06 PM, helmut.brandl@gmx.net wrote:
> I don't know which one I installed first.
> 
> The output of 'ocamlfind list | grep camlp4' is empty. 'camlp4' is not in the
> list. However opam installed it successfully.
> 
> I am working on linux distributed by archlinux.
> 

Try 'opam reinstall ocamlfind' (on the system switch).

--Edwin

Re: [Caml-list] Errors in installing 'lwt'

[Helmut Brandl]

Thanks a lot Edwin,

after the reinstallation of 'ocamlfind' everythink worked fine. I have 
now 'lwt' and 'js_of_ocaml' successfully installed on the system switch.

I gues it does not make sense to have the opam switch of 4.01 any 
longer. I will probably remove it since it consumes a lot of space on 
the harddisk.

Regards
Helmut


On 10/20/2014 11:21 AM, Török Edwin wrote:
> Try 'opam reinstall ocamlfind' (on the system switch).
>
> --Edwin
>

Re: [Caml-list] Errors in installing 'lwt'

[Török Edwin]

On 10/20/2014 07:37 PM, Helmut Brandl wrote:
> Thanks a lot Edwin,
> 
> after the reinstallation of 'ocamlfind' everythink worked fine. I have now 'lwt' and 'js_of_ocaml' successfully installed on the system switch.

Thanks, I was able to create a testcase and I opened an issue about improving the camlp4+system package here:
https://github.com/ocaml/opam-repository/issues/2900

Best regards,
--Edwin

Re: [Caml-list] Errors in installing 'lwt'

[Nicolas Boulay]

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Does a dependancies on the version of opam it-self exist ? Does a one year
old opam binaries could do the job ? (mageia 4)

2014-10-20 19:59 GMT+02:00 Török Edwin <edwin+ml-ocaml@etorok.net>:

> On 10/20/2014 07:37 PM, Helmut Brandl wrote:
> > Thanks a lot Edwin,
> >
> > after the reinstallation of 'ocamlfind' everythink worked fine. I have
> now 'lwt' and 'js_of_ocaml' successfully installed on the system switch.
>
> Thanks, I was able to create a testcase and I opened an issue about
> improving the camlp4+system package here:
> https://github.com/ocaml/opam-repository/issues/2900
>
> Best regards,
> --Edwin
>
>
> --
> Caml-list mailing list.  Subscription management and archives:
> https://sympa.inria.fr/sympa/arc/caml-list
> Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
> Bug reports: http://caml.inria.fr/bin/caml-bugs
>

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Re: [Caml-list] Errors in installing 'lwt'

[Nicolas Boulay]

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it works, but it seems that there is no dependancies checking on c library
like zlib, ssl, sqllite,...

Those "devel" library should be installed by "hand" or does i miss
something ? Is there a way to find all external dependancies list ?

2014-10-21 10:36 GMT+02:00 Francois Berenger <francois.berenger@inria.fr>:

> try and see
>
> On 10/21/2014 10:18 AM, Nicolas Boulay wrote:
>
>> Does a dependancies on the version of opam it-self exist ? Does a one
>> year old opam binaries could do the job ? (mageia 4)
>>
>> 2014-10-20 19:59 GMT+02:00 Török Edwin <edwin+ml-ocaml@etorok.net
>> <mailto:edwin+ml-ocaml@etorok.net>>:
>>
>>     On 10/20/2014 07:37 PM, Helmut Brandl wrote:
>>     > Thanks a lot Edwin,
>>     >
>>     > after the reinstallation of 'ocamlfind' everythink worked fine. I
>> have now 'lwt' and 'js_of_ocaml' successfully installed on the system
>> switch.
>>
>>     Thanks, I was able to create a testcase and I opened an issue about
>>     improving the camlp4+system package here:
>>     https://github.com/ocaml/opam-repository/issues/2900
>>
>>     Best regards,
>>     --Edwin
>>
>>
>>     --
>>     Caml-list mailing list.  Subscription management and archives:
>>     https://sympa.inria.fr/sympa/arc/caml-list
>>     Beginner's list: http://groups.yahoo.com/group/ocaml_beginners
>>     Bug reports: http://caml.inria.fr/bin/caml-bugs
>>
>>
>>
> --
> Regards,
> Francois.
>

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Re: [Caml-list] Errors in installing 'lwt'

[Török Edwin]

On 10/21/2014 11:55 PM, Nicolas Boulay wrote:
> it works, but it seems that there is no dependancies checking on c library like zlib, ssl, sqllite,...
> 
> Those "devel" library should be installed by "hand" or does i miss something ? Is there a way to find all external dependancies list ?

'opam install -e debian <package>' should print a list of all external dependencies to install on Debian.
You can try other distro instead of Debian, but not all opam packages have entries for all distributions.

Best regards,
--Edwin

Re: [Caml-list] Errors in installing 'lwt'

[Helmut Brandl]

Does not work either. 'opam' reinstalls 'camlp4' without any problems 
but then fails installing 'lwt'.

On 10/20/2014 09:20 AM, Francois Berenger wrote:
> stupid suggestion 2:
>
> opam reinstall camlp4
> opam install js_of_ocaml
>
> On 10/20/2014 04:18 PM, Helmut Brandl wrote:
>> I have tried this already. If I try to install 'camlp4' I just get the
>> message that 'camlp4' is already installed.
>>
>> On 10/20/2014 09:15 AM, Francois Berenger wrote:
>>> My stupid suggestion
>>>
>>> opam install camlp4
>>> opam install js_of_ocaml
>>>
>>> On 10/20/2014 03:59 PM, Helmut Brandl wrote:
>>>> Hello,
>>>>
>>>> I am trying to install 'js_of_ocaml' with 'opam' and run into some
>>>> problems. It seems that the ocaml compile cannot compile the 'lwt'
>>>> package.
>>>>
>>>> $opam list
>>>> Installed packages for system:
>>>> base-unix           base  Unix library distributed with the OCaml
>>>> compiler
>>>> camlp4     4.02.0+system  Camlp4 is a system for writing extensible
>>>> parsers for programming languages
>>>> cmdliner           0.9.5  Declarative definition of command line
>>>> interfaces for OCaml
>>>> menhir          20140422  LR(1) parser generator
>>>> ocamlfind          1.5.3  A library manager for OCaml
>>>> ppx_tools         0.99.1  Tools for authors of ppx rewriters and other
>>>> syntactic tools
>>>>
>>>> opam install js_of_ocaml
>>>> The following actions will be performed:
>>>>   - install lwt.2.4.6 [required by js_of_ocaml]
>>>>   - install js_of_ocaml.2.5
>>>> 2 to install | 0 to reinstall | 0 to upgrade | 0 to downgrade | 0 to
>>>> remove
>>>> Do you want to continue ? [Y/n]
>>>>
>>>> =-=-= Installing lwt.2.4.6 =-=-=
>>>> Building lwt.2.4.6:
>>>>    ./configure --prefix /home/helmut/.opam/system --disable-libev
>>>> --disable-react --disable-ssl --enable-unix --enable-extra
>>>> --disable-preemptive --disable-glib --enable-ppx
>>>>    make build
>>>>    make install
>>>> [ERROR] The compilation of lwt.2.4.6 failed.
>>>> Removing lwt.2.4.6.
>>>>    ocamlfind remove lwt
>>>>
>>>> [ERROR] Due to some errors while processing lwt.2.4.6, the following
>>>> actions will NOT proceed:
>>>>   - install js_of_ocaml.2.5
>>>>
>>>> ===== ERROR while installing lwt.2.4.6 =====
>>>> # opam-version 1.1.1
>>>> # os           linux
>>>> # command      ./configure --prefix /home/helmut/.opam/system
>>>> --disable-libev --disable-react --disable-ssl --enable-unix
>>>> --enable-extra --disable-preemptive --disable-glib --enable-ppx
>>>> # path         /home/helmut/.opam/system/build/lwt.2.4.6
>>>> # compiler     system (4.02.0)
>>>> # exit-code    1
>>>> # env-file
>>>> /home/helmut/.opam/system/build/lwt.2.4.6/lwt-25223-ffb3fd.env
>>>> # stdout-file
>>>> /home/helmut/.opam/system/build/lwt.2.4.6/lwt-25223-ffb3fd.out
>>>> # stderr-file
>>>> /home/helmut/.opam/system/build/lwt.2.4.6/lwt-25223-ffb3fd.err
>>>> ### stderr ###
>>>> # ...[truncated]
>>>> # W: Failure("Command ''/home/helmut/.opam/system/bin/ocamlfind' query
>>>> -format %d camlp4 > '/tmp/oasis-c39eab.txt'' terminated with error
>>>> code 2")
>>>> # ocamlfind: Package `camlp4' not found
>>>> # W: Failure("Command ''/home/helmut/.opam/system/bin/ocamlfind' query
>>>> -format %d camlp4 > '/tmp/oasis-5e24a6.txt'' terminated with error
>>>> code 2")
>>>> # ocamlfind: Package `camlp4.quotations.o' not found
>>>> # W: Failure("Command ''/home/helmut/.opam/system/bin/ocamlfind' query
>>>> -format %d camlp4.quotations.o > '/tmp/oasis-f94904.txt'' terminated
>>>> with error code 2")
>>>> # E: Cannot find buildable internal library 'lwt-preemptive' when
>>>> checking build depends
>>>> # E: Cannot find findlib package camlp4
>>>> # E: Cannot find findlib package camlp4.extend
>>>> # E: Cannot find findlib package camlp4.quotations.o
>>>> # E: Failure("4 configuration errors")
>>>>
>>>> 'opam install js_of_ocaml' failed.
>>>>
>>>>
>>>> Can anybody help (or if this list is not the right location to ask can
>>>> you redirect me)?
>>>>
>>>> Thanks in advance
>>>> Helmut
>>>>
>>>
>>
>

Re: [Caml-list] Errors in installing 'lwt'

[John Whitington]

Hi,

Helmut Brandl wrote:
> Does not work either. 'opam' reinstalls 'camlp4' without any problems
> but then fails installing 'lwt'.

You haven't mentioned what platform you're using. There's a known issue 
on OS X with 2.4.6, for example:

https://github.com/ocsigen/lwt/issues/91

Thanks,

-- 
John Whitington
Director, Coherent Graphics Ltd
http://www.coherentpdf.com/

Re: [Caml-list] Errors in installing 'lwt'

[Helmut Brandl]

My platform is the 32bit version of the archlinux distribution on x86. I 
have got the ocaml base installation and opam via the distribution and 
tried to install packages via 'opam install ...'.

Everything went fine until 'opam' tried to install 'lwt'.



On 10/20/2014 09:50 AM, John Whitington wrote:
> Hi,
>
> Helmut Brandl wrote:
>> Does not work either. 'opam' reinstalls 'camlp4' without any problems
>> but then fails installing 'lwt'.
>
> You haven't mentioned what platform you're using. There's a known 
> issue on OS X with 2.4.6, for example:
>
> https://github.com/ocsigen/lwt/issues/91
>
> Thanks,
>

Re: [Caml-list] Errors in installing 'lwt'

[Helmut Brandl]

I am puzzled by a comment from Török. I tried

$ocamlfind list
bigarray            (version: [distributed with Ocaml])
bytes               (version: [distributed with OCaml 4.02 or above])
cmdliner            (version: 0.9.5)
compiler-libs       (version: [distributed with Ocaml])
compiler-libs.bytecomp (version: [distributed with Ocaml])
compiler-libs.common (version: [distributed with Ocaml])
compiler-libs.optcomp (version: [distributed with Ocaml])
compiler-libs.toplevel (version: [distributed with Ocaml])
dynlink             (version: [distributed with Ocaml])
findlib             (version: 1.5.3)
graphics            (version: [distributed with Ocaml])
menhirLib           (version: 20140422)
num                 (version: [distributed with Ocaml])
num-top             (version: 1.5.3)
num.core            (version: [internal])
ocamlbuild          (version: [distributed with Ocaml])
ppx_tools           (version: 0.99)
ppx_tools.metaquot  (version: 0.99)
stdlib              (version: [distributed with Ocaml])
str                 (version: [distributed with Ocaml])
threads             (version: [distributed with Ocaml])
threads.posix       (version: [internal])
threads.vm          (version: [internal])
unix                (version: [distributed with Ocaml])

There is no 'camlp4' in this list despite the fact that 'opam' installed 
it without any problems.

Re: [Caml-list] Errors in installing 'lwt'

[Francois Berenger]

As a workaround, I would recommend having a fresh ocaml installed by opam.

It always work nicer in this way, in my experience (I use the ocaml
installed by opam switching, not the one installed system-wide).

On 10/20/2014 04:56 PM, Helmut Brandl wrote:
> My platform is the 32bit version of the archlinux distribution on x86. I
> have got the ocaml base installation and opam via the distribution and
> tried to install packages via 'opam install ...'.
>
> Everything went fine until 'opam' tried to install 'lwt'.
>
>
>
> On 10/20/2014 09:50 AM, John Whitington wrote:
>> Hi,
>>
>> Helmut Brandl wrote:
>>> Does not work either. 'opam' reinstalls 'camlp4' without any problems
>>> but then fails installing 'lwt'.
>>
>> You haven't mentioned what platform you're using. There's a known
>> issue on OS X with 2.4.6, for example:
>>
>> https://github.com/ocsigen/lwt/issues/91
>>
>> Thanks,
>>
>

-- 
Regards,
Francois.

Re: [Caml-list] Errors in installing 'lwt'

[Helmut Brandl]

How do I install ocaml by opam? The command 'opam install ocaml' does 
not work.

What is the difference? My ocaml system works fine and I don't want to 
compromise it because I need it. Can 2 versions of ocaml coexist without 
any interference?

On 10/20/2014 10:08 AM, Francois Berenger wrote:
> As a workaround, I would recommend having a fresh ocaml installed by 
> opam.
>
> It always work nicer in this way, in my experience (I use the ocaml
> installed by opam switching, not the one installed system-wide).
>
> On 10/20/2014 04:56 PM, Helmut Brandl wrote:
>> My platform is the 32bit version of the archlinux distribution on x86. I
>> have got the ocaml base installation and opam via the distribution and
>> tried to install packages via 'opam install ...'.
>>
>> Everything went fine until 'opam' tried to install 'lwt'.
>>
>>
>>
>> On 10/20/2014 09:50 AM, John Whitington wrote:
>>> Hi,
>>>
>>> Helmut Brandl wrote:
>>>> Does not work either. 'opam' reinstalls 'camlp4' without any problems
>>>> but then fails installing 'lwt'.
>>>
>>> You haven't mentioned what platform you're using. There's a known
>>> issue on OS X with 2.4.6, for example:
>>>
>>> https://github.com/ocsigen/lwt/issues/91
>>>
>>> Thanks,
>>>
>>
>

Re: [Caml-list] Errors in installing 'lwt'

[Francois Berenger]

On 10/20/2014 05:19 PM, Helmut Brandl wrote:
> How do I install ocaml by opam? The command 'opam install ocaml' does
> not work.

opam switch 4.01.0 # just an example version
eval `opam config env` # use it
opam install lwt # your initial goal

> What is the difference? My ocaml system works fine and I don't want to
> compromise it because I need it.

It won't be compromised in any way, opam will just ignore it.

> Can 2 versions of ocaml coexist without any interference?

That's one of the many goals of OPAM, I believe.
OPAM's switch command allows you to "jump" between ocaml versions.

> On 10/20/2014 10:08 AM, Francois Berenger wrote:
>> As a workaround, I would recommend having a fresh ocaml installed by
>> opam.
>>
>> It always work nicer in this way, in my experience (I use the ocaml
>> installed by opam switching, not the one installed system-wide).
>>
>> On 10/20/2014 04:56 PM, Helmut Brandl wrote:
>>> My platform is the 32bit version of the archlinux distribution on x86. I
>>> have got the ocaml base installation and opam via the distribution and
>>> tried to install packages via 'opam install ...'.
>>>
>>> Everything went fine until 'opam' tried to install 'lwt'.
>>>
>>>
>>>
>>> On 10/20/2014 09:50 AM, John Whitington wrote:
>>>> Hi,
>>>>
>>>> Helmut Brandl wrote:
>>>>> Does not work either. 'opam' reinstalls 'camlp4' without any problems
>>>>> but then fails installing 'lwt'.
>>>>
>>>> You haven't mentioned what platform you're using. There's a known
>>>> issue on OS X with 2.4.6, for example:
>>>>
>>>> https://github.com/ocsigen/lwt/issues/91
>>>>
>>>> Thanks,
>>>>
>>>
>>
>
>

-- 
Regards,
Francois.

Re: [Caml-list] Errors in installing 'lwt'

[Helmut Brandl]

Thanks for the hint Francois. The command sequence you proposed worked 
successfully.

However can you explain to me what I have now. I think I have now two 
versions of the ocaml compiler installed, one system wide (4.02.0) and 
one installed by opam (4.01.0).

If I use a fresh shell I still get version 4.02 until I issue the 'eval' 
command to get the new paths. If I try to switch back to 4.02 opam tries 
to install 4.02 from scratch, i.e. it does not use the system installation.

Is there any possibility to switch back to the system installation in 
the same shell or do I need to use a fresh shell?

I still feel uncomfortable because I don't know why the installation of 
'lwt' fails with my system installation of ocaml.

Regards
Helmut


On 10/20/2014 10:25 AM, Francois Berenger wrote:
> On 10/20/2014 05:19 PM, Helmut Brandl wrote:
>> How do I install ocaml by opam? The command 'opam install ocaml' does
>> not work.
>
> opam switch 4.01.0 # just an example version
> eval `opam config env` # use it
> opam install lwt # your initial goal
>
>> What is the difference? My ocaml system works fine and I don't want to
>> compromise it because I need it.
>
> It won't be compromised in any way, opam will just ignore it.
>
>> Can 2 versions of ocaml coexist without any interference?
>
> That's one of the many goals of OPAM, I believe.
> OPAM's switch command allows you to "jump" between ocaml versions.
>
>> On 10/20/2014 10:08 AM, Francois Berenger wrote:
>>> As a workaround, I would recommend having a fresh ocaml installed by
>>> opam.
>>>
>>> It always work nicer in this way, in my experience (I use the ocaml
>>> installed by opam switching, not the one installed system-wide).
>>>
>>> On 10/20/2014 04:56 PM, Helmut Brandl wrote:
>>>> My platform is the 32bit version of the archlinux distribution on 
>>>> x86. I
>>>> have got the ocaml base installation and opam via the distribution and
>>>> tried to install packages via 'opam install ...'.
>>>>
>>>> Everything went fine until 'opam' tried to install 'lwt'.
>>>>
>>>>
>>>>
>>>> On 10/20/2014 09:50 AM, John Whitington wrote:
>>>>> Hi,
>>>>>
>>>>> Helmut Brandl wrote:
>>>>>> Does not work either. 'opam' reinstalls 'camlp4' without any 
>>>>>> problems
>>>>>> but then fails installing 'lwt'.
>>>>>
>>>>> You haven't mentioned what platform you're using. There's a known
>>>>> issue on OS X with 2.4.6, for example:
>>>>>
>>>>> https://github.com/ocsigen/lwt/issues/91
>>>>>
>>>>> Thanks,
>>>>>
>>>>
>>>
>>
>>
>

Re: [Caml-list] Errors in installing 'lwt'

[Marek Kubica]

On Mon, 20 Oct 2014 11:24:10 -0500
Helmut Brandl <helmut.brandl@gmx.net> wrote:

> However can you explain to me what I have now. I think I have now two 
> versions of the ocaml compiler installed, one system wide (4.02.0)
> and one installed by opam (4.01.0).

Why 4.01.0? You could run 4.02.1 from OPAM, that has some nice
features :-)

> Is there any possibility to switch back to the system installation in 
> the same shell or do I need to use a fresh shell?

opam switch system

And then do the eval-dance :-)

> I still feel uncomfortable because I don't know why the installation
> of 'lwt' fails with my system installation of ocaml.

Im my experience, the Arch Linux ocaml/camlp4 packages are busted, I
filed a bug but nothing happened:
<https://bugs.archlinux.org/task/41907?dev=162>

(Also, keep in mind to switch to the system compiler when building
packages from AUR, because having the OPAM compiler in the path messes
things up).

regards,
Marek

Re: [Caml-list] Errors in installing 'lwt'

[Daniel Bünzli]

Le lundi, 20 octobre 2014 à 17:19, Helmut Brandl a écrit :

> How do I install ocaml by opam? The command 'opam install ocaml' does  
> not work.

opam switch --help
  
> What is the difference?  

This will install an OCaml compiler from scratch in your .opam directory.
  
> My ocaml system works fine and I don't want to
> compromise it because I need it.  

This won't compromise your system compiler.
  
> Can 2 versions of ocaml coexist without  
> any interference?

With opam yes. See here http://opam.ocaml.org/doc/1.2/Usage.html#opamswitch

Best,

Daniel