cpplint incorrectly labels C++17 headers as C headers

[jacobperron]

Consider this example:

// Copyright 2021 Jacob Perron
#include <iostream>
#include <optional>

int main(void)
{
  return 0;
}

IIUC, following the Google C++ guide, it has the correct, alphabetically sorted, list of included C++ headers.

However, ament_cpplint complains that <optional> is a C header and should appear before <iostream>.

I've noticed that the same issue happens for all C++17 headers, e.g. <filesystem>. cpplint doesn't seem to be aware of them. Perhaps there is a patch upstream to fix this, but I haven't taken a look.

[wjwwood]

This also comes up for #include <variant>

[zflat]

@jacobperron Try building the latest cppcheck release from source (https://github.com/danmar/cppcheck/releases). If the problem persists then a ticket can be opened at https://trac.cppcheck.net/wiki.

[jacobperron]

@zflat The issue is with cpplint, not cppcheck.

cpplint.py was copied from the Google style guide here: https://github.com/google/styleguide/blob/71ec7f1e524969c19ce33cfc72e8e023f2b98ee2/cpplint/cpplint.py

I tried pulling in changes from upstream, but it doesn't appear to fix the issue. We may have to come up with a patch ourselves.

[jacobperron]

Updating to a different version of cpplint seems to fix this issue. I've opened a PR #324 proposing we switch to tracking this fork: https://github.com/cpplint/cpplint

[aprotyas]

@zflat The issue is with cpplint, not cppcheck.

On that note, this also happens with cppcheck. ros2/geometry2#464 had to specify the language manually, but that is orthogonal to this issue.