/usr/include/diagnostics/extensions/ is in libdiagnostics-dev 0.3.3-10+b1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/diagnostics/extensions/instrumentation/
/usr/include/diagnostics/extensions/instrumentation/annotations.hpp
/usr/include/diagnostics/extensions/instrumentation/load_symbol.hpp
/usr/include/diagnostics/extensions/memory/
/usr/include/diagnostics/extensions/memory/allocation_database.hpp
/usr/include/diagnostics/extensions/memory/allocation_record.hpp
/usr/include/diagnostics/extensions/memory/annotations.hpp
/usr/include/diagnostics/extensions/memory/malloc_allocator.hpp
/usr/include/diagnostics/extensions/memory/names.hpp
/usr/include/diagnostics/extensions/memory/namespace.hpp
/usr/include/diagnostics/extensions/memory/operators.hpp
/usr/include/diagnostics/extensions/memory/tick.hpp
/usr/include/diagnostics/extensions/stacktrace/
/usr/include/diagnostics/extensions/stacktrace/descriptor.hpp
/usr/include/diagnostics/extensions/stacktrace/error.hpp
/usr/include/diagnostics/extensions/stacktrace/frame_visitor.hpp
/usr/include/diagnostics/extensions/stacktrace/handler.hpp
/usr/include/diagnostics/extensions/stacktrace/namespace.hpp
/usr/include/diagnostics/extensions/stacktrace/posix.hpp
/usr/include/diagnostics/extensions/stacktrace/process.hpp
/usr/include/diagnostics/extensions/stacktrace/raw_process.hpp
/usr/include/diagnostics/extensions/stacktrace/signal.hpp