clang vs gcc linking problem

[Artifex Maximus]

Hello!

Absolutely not a flame war but would like to switch to clang in a
project. Project uses ncurses. gcc works well but the executable fails
when compiled other than -O0. Then I think I should change to clang
which will becomes the default compiler in FreeBSD. With clang at
linking time I got the following error:

/usr/local/bin/ld: display/libsub_display.a(canvas.o): undefined
reference to symbol 'keypad'
/usr/local/bin/ld: note: 'keypad' is defined in DSO
/usr/local/lib/libtinfow.so.6.0 so try adding it to the linker command
line
/usr/local/lib/libtinfow.so.6.0: could not read symbols: Invalid operation
clang: error: linker command failed with exit code 1 (use -v to see invocation)
*** Error code 1

With exactly the same flags gcc links successful. Any idea where is
the problem and what is the solution?

Thanks,
a