# Flexlink error when compiling OCaml 4.07.1 on Windows 10

**URL:** <https://discuss.ocaml.org/t/flexlink-error-when-compiling-ocaml-4-07-1-on-windows-10/3391>\
**Category:** Learning\
**Tags:** windows, build\
**Created:** [February 21, 2019, 5:24pm UTC](https://discuss.ocaml.org/t/flexlink-error-when-compiling-ocaml-4-07-1-on-windows-10/3391 "2019-02-21T17:24:08Z")\
**Posts on this page:** 8\
**Page:** 1

<div class="post-metadata">

**Author:** ![thierry-martinez](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/thierry-martinez/32/1481_2.png) [@thierry-martinez](https://discuss.ocaml.org/u/thierry-martinez)\
**Post date:** [February 21, 2019, 5:24pm UTC](https://discuss.ocaml.org/t/flexlink-error-when-compiling-ocaml-4-07-1-on-windows-10/3391/1 "2019-02-21T17:24:08Z")

</div>

I am learning how to compile OCaml 4.07.1 on Windows 10. `make world` and `make world.opt` both fail with the following error:

```auto
make -C byterun all
make[1]: Entering directory '/home/ci/ocaml-4.07.1/byterun'
flexlink -x64 -merge-manifest -stack 33554432 -exe -link "/ENTRY:wmainCRTStartup" -o ocamlrun.exe prims.obj libcamlrun.lib advapi32.lib ws2_32.lib version.lib
** Cannot resolve symbols for descriptor object:
 __iob_func
 sprintf
make[1]: *** [Makefile:187: ocamlrun.exe] Error 2
make[1]: Leaving directory '/home/ci/ocaml-4.07.1/byterun'
make: *** [Makefile:389: coldstart] Error 2

```

I am under Windows 10 (1809, OS build 17763.316) with Visual Studio Community 2017.  
`cl` displays `Microsoft (R) C/C++ Optimizing Compiler Version 19.16.27027.1 for x64`.  
`flexlink` displays `FlexDLL version 0.37`.  
I have the following cygwin packages installed:

```auto
$ cygcheck -c
Cygwin Package Information
Package Version Status
_autorebase 001007-1 OK
alternatives 1.3.30c-10 OK
autoconf 13-1 OK
autoconf2.1 2.13-12 OK
autoconf2.5 2.69-4 OK
automake 10-1 OK
automake1.10 1.10.3-3 OK
automake1.11 1.11.6-3 OK
automake1.12 1.12.6-3 OK
automake1.13 1.13.4-2 OK
automake1.14 1.14.1-3 OK
automake1.15 1.15.1-1 OK
automake1.9 1.9.6-11 OK
base-cygwin 3.8-1 OK
base-files 4.2-4 OK
bash 4.4.12-3 OK
bzip2 1.0.6-3 OK
ca-certificates 2.22-1 OK
coreutils 8.26-2 OK
cygutils 1.4.16-2 OK
cygwin 3.0.1-1 OK
dash 0.5.9.1-1 OK
diffutils 3.5-2 OK
editrights 1.03-1 OK
file 5.32-1 OK
findutils 4.6.0-1 OK
gawk 4.2.1-1 OK
getent 2.18.90-4 OK
grep 3.0-2 OK
groff 1.22.3-1 OK
gzip 1.8-1 OK
hostname 3.13-1 OK
info 6.5-2 OK
ipc-utils 1.0-2 OK
less 530-1 OK
libargp 20110921-3 OK
libattr1 2.4.48-2 OK
libblkid1 2.32.1-1 OK
libbz2_1 1.0.6-3 OK
libcrypt0 2.1-1 OK
libdb5.3 5.3.28-2 OK
libfdisk1 2.32.1-1 OK
libffi6 3.2.1-2 OK
libgc1 7.6.10-1 OK
libgcc1 7.4.0-1 OK
libgdbm4 1.12-1 OK
libgmp10 6.1.2-1 OK
libguile2.0_22 2.0.14-3 OK
libiconv 1.14-3 OK
libiconv2 1.14-3 OK
libintl8 0.19.8.1-2 OK
libltdl7 2.4.6-6 OK
liblzma5 5.2.3-1 OK
libmpfr6 4.0.2-1 OK
libncursesw10 6.0-12.20171125 OK
libopenssl100 1.0.2p-1 OK
libp11-kit0 0.23.10-1 OK
libpcre1 8.40-3 OK
libpipeline1 1.4.0-1 OK
libpopt-common 1.16-2 OK
libpopt0 1.16-2 OK
libreadline7 7.0.3-3 OK
libsigsegv2 2.10-2 OK
libsmartcols1 2.32.1-1 OK
libssp0 6.4.0-4 OK
libstdc++6 7.4.0-1 OK
libtasn1_6 4.13-1 OK
libunistring2 0.9.10-1 OK
libuuid1 2.32.1-1 OK
login 1.12-1 OK
m4 1.4.18-1 OK
make 4.2.1-2 OK
man-db 2.7.6.1-1 OK
mintty 2.9.6-0 OK
ncurses 6.0-12.20171125 OK
openssl 1.0.2p-1 OK
p11-kit 0.23.10-1 OK
p11-kit-trust 0.23.10-1 OK
perl 5.26.3-1 OK
perl-Carp 1.38-2 OK
perl-Test-Harness 3.42-1 OK
perl_autorebase 5.26.3-1 OK
perl_base 5.26.3-1 OK
rebase 4.4.4-1 OK
run 1.3.4-2 OK
sed 4.4-1 OK
tar 1.29-1 OK
terminfo 6.0-12.20171125 OK
texinfo 6.5-2 OK
tzcode 2018i-1 OK
tzdata 2018i-1 OK
util-linux 2.32.1-1 OK
vim-minimal 8.0.1567-1 OK
which 2.20-2 OK
xz 5.2.3-1 OK
zlib0 1.2.11-1 OK

```

Thank you for any help!

---

<div class="post-metadata">

**Author:** ![andreypopp](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/andreypopp/32/97_2.png) [@andreypopp](https://discuss.ocaml.org/u/andreypopp)\
**Post date:** [February 21, 2019, 8:32pm UTC](https://discuss.ocaml.org/t/flexlink-error-when-compiling-ocaml-4-07-1-on-windows-10/3391/2 "2019-02-21T20:32:16Z")

</div>

In esy we build OCaml compiler on Windows using mingw toolchain.

We do have a [fork of flexdll](https://github.com/esy-ocaml/flexdll) though but as far as I know most of the fixes are related to long file path on Windows + a fix for linking C++ code.

I’m not an expert here, @bryphe did this and knows better.

---

<div class="post-metadata">

**Author:** ![XVilka](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/xvilka/32/5334_2.png) [@XVilka](https://discuss.ocaml.org/u/XVilka)\
**Post date:** [February 22, 2019, 5:20am UTC](https://discuss.ocaml.org/t/flexlink-error-when-compiling-ocaml-4-07-1-on-windows-10/3391/3 "2019-02-22T05:20:30Z")

</div>

Huh, and people were telling me OCaml works smoothly on Windows: [OCaml and Windows](https://discuss.ocaml.org/t/ocaml-and-windows/3282)

---

<div class="post-metadata">

**Author:** ![thierry-martinez](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/thierry-martinez/32/1481_2.png) [@thierry-martinez](https://discuss.ocaml.org/u/thierry-martinez)\
**Post date:** [February 22, 2019, 12:20pm UTC](https://discuss.ocaml.org/t/flexlink-error-when-compiling-ocaml-4-07-1-on-windows-10/3391/4 "2019-02-22T12:20:00Z")

</div>

Thank you for suggesting mingw. Unfortunately, I just tried and got the same error with mingw.

---

<div class="post-metadata">

**Author:** ![andreypopp](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/andreypopp/32/97_2.png) [@andreypopp](https://discuss.ocaml.org/u/andreypopp)\
**Post date:** [February 22, 2019, 1:57pm UTC](https://discuss.ocaml.org/t/flexlink-error-when-compiling-ocaml-4-07-1-on-windows-10/3391/5 "2019-02-22T13:57:14Z")

</div>

Looks like a related issue: [https://caml.inria.fr/mantis/view.php?id=7263](https://caml.inria.fr/mantis/view.php?id=7263)

(are you sure it picked mingw toolchain and not msvc again?)

---

<div class="post-metadata">

**Author:** ![thierry-martinez](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/thierry-martinez/32/1481_2.png) [@thierry-martinez](https://discuss.ocaml.org/u/thierry-martinez)\
**Post date:** [February 22, 2019, 3:21pm UTC](https://discuss.ocaml.org/t/flexlink-error-when-compiling-ocaml-4-07-1-on-windows-10/3391/6 "2019-02-22T15:21:44Z")

</div>

Thank you very much for exhuming this issue: that makes me realize that I missed the paragraph in `README.win32.adoc` telling that to use recent versions of Visual Studio, I have to bootstrap `flexdll` (I was using the binary version distributed by @alainfrisch).

It works much better now… but `make world` still fails at

```auto
../../boot/ocamlrun ../../tools/ocamlmklib -oc unix accept.obj bind.obj channels.obj close.obj
close_on.obj connect.obj createprocess.obj dup.obj dup2.obj errmsg.obj envir.obj getpeername.ob
j getpid.obj getsockname.obj gettimeofday.obj isatty.obj link.obj listen.obj lockf.obj lseek.ob
j nonblock.obj mkdir.obj mmap.obj open.obj pipe.obj read.obj readlink.obj rename.obj select.obj
 sendrecv.obj shutdown.obj sleep.obj socket.obj sockopt.obj startup.obj stat.obj symlink.obj sy
stem.obj times.obj unixsupport.obj windir.obj winwait.obj write.obj winlist.obj winworker.obj w
indbug.obj utimes.obj access.obj addrofstr.obj chdir.obj chmod.obj cst2constr.obj cstringv.obj
execv.obj execve.obj execvp.obj exit.obj getaddrinfo.obj getcwd.obj gethost.obj gethostname.obj
 getnameinfo.obj getproto.obj getserv.obj gmtime.obj mmap_ba.obj putenv.obj rmdir.obj socketadd
r.obj strofaddr.obj time.obj unlink.obj -ldopt ws2_32.lib -ldopt advapi32.lib
'..\..\boot\ocamlrun' is not recognized as an internal or external command,
operable program or batch file.

```

`make world.opt` fails with a similar error. I found this issue [https://caml.inria.fr/mantis/view.php?id=408](https://caml.inria.fr/mantis/view.php?id=408) but it does not seem to be the same problem, since I do have a file `boot/ocamlrun.exe`, which is executable and which works properly.

---

<div class="post-metadata">

**Author:** ![nojb](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/nojb/32/519_2.png) [@nojb](https://discuss.ocaml.org/u/nojb)\
**Post date:** [February 27, 2019, 6:16am UTC](https://discuss.ocaml.org/t/flexlink-error-when-compiling-ocaml-4-07-1-on-windows-10/3391/7 "2019-02-27T06:16:49Z")

</div>

Your original problem is due to the fact that `flexdll` includes a small runtime support library, and the binary version is compiled with a Visual Studio \< 2015 which is not binary compatible with VS \>= 2015.

You have two options:

1. Re-compile `flexdll` from source and use that when compiling OCaml
2. Compile OCaml with the “bootstrapped” `flexdll`

Option 2. is easier and should work. Just make sure to start from a clean repository and build things in the right order: `make flexdll`; `make world.opt`.

---

<div class="post-metadata">

**Author:** ![nojb](https://sea2.discourse-cdn.com/flex020/user_avatar/discuss.ocaml.org/nojb/32/519_2.png) [@nojb](https://discuss.ocaml.org/u/nojb)\
**Post date:** [February 27, 2019, 6:55am UTC](https://discuss.ocaml.org/t/flexlink-error-when-compiling-ocaml-4-07-1-on-windows-10/3391/8 "2019-02-27T06:55:47Z")

</div>

> [@thierry-martinez](#):
>
> ```auto
> '..\..\boot\ocamlrun' is not recognized as an internal or external command,
> operable program or batch file.
> 
> ```

This error is a bit strange because it is a `cmd.exe` error, which you should not get if you are building under Cygwin.