Cannot install via opam on FreeBSD

[eretz]

Hello mister Garrigue,

While trying to install labltk via opam, I received this error message :

<><> Processing actions <><><><><><><><><><><><><><><><><><><><><><><><><><><><>
[ERROR] The compilation of conf-tcl failed at "/bin/sh check.sh".

#=== ERROR while compiling conf-tcl.1 =========================================#
# context     2.0.0 | freebsd/x86_64 | ocaml-system.4.02.3 | https://opam.ocaml.org#1b1f3945
# path        /usr/home/emmanuel/.opam/default/.opam-switch/build/conf-tcl.1
# command     /bin/sh check.sh
# exit-code   1
# env-file    /usr/home/emmanuel/.opam/log/conf-tcl-1714-9b8556.env
# output-file /usr/home/emmanuel/.opam/log/conf-tcl-1714-9b8556.out
### output ###
# compiletest.c:2:10: fatal error: 'tcl.h' file not found
# #include <tcl.h>
#          ^~~~~~~
# 1 error generated.

My FreeBSD version is 11.1-RELEASE

For information, the file tcl.h does exists in my PC, at /usr/local/include/tcl8.6/generic/tcl.h.
There's a symbolic link pointing to it at : /usr/local/include/tcl8.6/tcl.h

[eretz]

I've used this workaround to solve the problem :
I edited my .profile and added this line :

export C_INCLUDE_PATH=/usr/local/include/:/usr/local/include/tcl8.6/:/usr/local/include/tk8.6/

But it seems to me that it's only a workaround :-)

[garrigue]

According to the opam file, conf-tcl is maintained by the Tcl core team, and issues should go directly to the opam-repository database.
Looking at the package itself, it seems that on your machine pkg-config tcl requires setting the above path to work properly, which is strange.

Since the C_INCLUDE_PATH variable is not used by LablTk, which has already logic for looking in /usr/local/tcl8.6 and /usr/local/include/tk8.6, there is no problem in LablTk itself. But it might actually be better to use the same method as conf-tcl, if it proves robust enough.