The TCL header should be included with #include <tcl.h>, not #include <tcl/tcl.h>

[yurivict]

Error:

invoke CC
library/tcltk0.c:2:10: fatal error: 'tcl/tcl.h' file not found
#include <tcl/tcl.h>
         ^~~~~~~~~~~

This is because tcl.h is installed into this path:

$ pkg info -l tcl86 | grep "tcl\.h"
    /usr/local/include/tcl8.6/generic/tcl.h
    /usr/local/include/tcl8.6/tcl.h

Multiple versions of TCL can be installed concurrently. The expected way to include tcl.h is #include <tcl.h>. CFLAGS should contain flags to include proper version of TCL.

FreeBSD 13.1

[sasagawa888]

I fixed it.