Hmm, @kugel- `cpp_std` isn't a valid named parameter to `shared_library()` (see the configure output @codebrainz posted), it should probably be in the `cpp_args` if you want to apply it to only the Scintilla part of the build. But personally I would add it in `add_project_options()` as per https://mesonbuild.com/howtox.html#set-default-cc-language-version. Might as well make it global, only Scintilla is C++ anyway.