Cannot pass non-trivial object of type 'xx' to variadic function - Rebuild of the Debian archive with clang

"Cannot pass non-trivial object of type 'xx' to variadic function" build failure(s) — clang 10.0.0

Package	Version	Supposed error message	Full log	Bug report
ffmpegfs	1.98-3	./logging.h:321:99: error: cannot pass object of non-trivial type 'std::__cxx11::basic_string' through variadic function; call will abort at runtime [-Wnon-pod-varargs]	Log
lomiri-api	0.1.0-5	GObjectMemory_test.cpp:232:38: error: cannot pass object of non-trivial type 'internal::GlibAssigner > >' through variadic function; call will abort at runtime [-Wnon-pod-varargs]	Log

2 errors