clipp::option and clipp::group initialization issue

[robabateman]

Consider this code:
https://github.com/muellan/clipp/blob/master/examples/options.cpp#L23
Here's the code for context:

    auto cli = (
        option("-a").set(a)                  % "activates a",
        option("-b").set(b)                  % "activates b",
        option("-c", "--noc").set(c,false)   % "deactivates c",
        option("--hi")([]{cout << "hi!\n";}) % "says hi");

Effectively what we have here is:

auto cli = (expr1, expr2, expr3, expr4);

This generates the following level 1 compiler warning under visual C++ for example:

warning C4548: expression before comma has no effect; expected expression with side-effect

I assume this is just an oversight in the examples?
So, is there any advice on the correct way to initialize a group from a set of options?

[robabateman]

Additional Context: I've got a platform/compiler combination where this code fails when building with pre-compiled headers enabled. Arguably that's probably a compiler bug, but the compiler isn't likely to be fixed anytime soon. I can't give too many details beyond that I'm afraid (I'm under an NDA). Besides that, it's a bit annoying given we also build with warnings as errors enabled....