NL.4: Maintain a consistent indentation style

Use a tool.

clang-format

NL.8: Use a consistent naming style

Would be possible except for the use of libraries with varying conventions.

clang-tidy: readability-identifier-naming
clang-format

NL.9: Use ALL_CAPS for macro names only

Flag macros with lower-case letters
Flag ALL_CAPS non-macro names

clang-tidy: readability-identifier-naming

NL.10: Avoid CamelCase

Impossible

clang-tidy: readability-identifier-naming

NL.15: Use spaces sparingly

clang-format

NL.11: Make literals readable

Flag long digit sequences. The trouble is to define "long"; maybe 7.

no enforcement

NL.16: Use a conventional class member declaration order

Flag departures from the suggested order. There will be a lot of old code that doesn't follow this rule.

no enforcement

NL.17: Use K&R-derived layout

If you want enforcement, use an IDE to reformat.

clang-format

NL.18: Use C++-style declarator layout

Impossible in the face of history.

clang-format

NL.20: Don't place two statements on the same line

Easy

clang-format

NL.21: Declare one name (only) per declaration

nothing

no enforcement

NL.25: Don't use void as an argument type

no enforcement

NL.26: Use conventional const notation

Flag const used as a suffix for a type.

no enforcement