The use of obsolete Contax / Yashica lenses on Canon EOS bodies is relatively common, but some exotic combinations of lenses and bodies are little documented and their compatibility unknown. I have now had some experience adapting two C/Y lenses  on two Canon EOS bodies and I can report the results, unfortunately not enthusiastically.

Camera Lens Result: mirror Result: meter
EOS 5 Carl Zeiss Tessar 45/2.8 hits the lens off about 1-1.5 EV
EOS 5 Carl Zeiss Sonnar 135/2.8 hits the lens off about 1-1.5 EV
EOS 1n Carl Zeiss Tessar 45/2.8 hits the lens OK
EOS 1n Carl Zeiss Sonnar 135/2.8 clear OK

By the way, the EOS 5 has the undeniable advantage of a very silent operation over EOS 1n but, besides this, the 1n is clearly a better camera.