Unused function - Rebuild of the Debian archive with clang

"Unused function" build failure(s)
clang 6.0

-Wall -Werror are including the option -Wunused-function. Without not the case with g++

namespace { 
   void dummy_for_semicolon_do_not_use();
}

Versions: 2.9 - 3.0 - 3.1 - 3.2 - 3.3 - 3.4 - 3.4.2 - 3.5.0 - 3.6.0 - 3.8.1 - 3.9.1 - 4.0.1 - 5.0 - 6.0 - 8.0.1 - 9.0.1 - 10.0.0 - 11.0.0 - 12.0.1 - 13.0.0

Package	Version	Supposed error message	Full log
ddcutil	0.8.6-1	vcp_feature_set.c:225:1: error: unused function 'unopaque_feature_set' [-Werror,-Wunused-function]	Log
infinipath-psm	3.3+20.604758e7-5	ptl.c:539:1: error: unused function 'ips_lock_shared_context' [-Werror,-Wunused-function]	Log
libcerf	1.3-2	w_of_z.c:79:21: error: unused function 'cpolar' [-Werror,-Wunused-function]	Log

3 errors

Debian Package rebuild