enh(c) Update keyword list for C11/C18

[joshgoebel]

Pulling this out because we should eventually apply this to our C grammar (removing the C++ keywords and types, etc).

---

The full list of keywords for C11/C18 is

                auto                          if                             unsigned
                break                         inline                         void
                case                          int                            volatile
                char                          long                           while
                const                         register                       _Alignas
                continue                      restrict                       _Alignof
                default                       return                         _Atomic
                do                            short                          _Bool
                double                        signed                         _Complex
                else                          sizeof                         _Generic
                enum                          static                         _Imaginary
                extern                        struct                         _Noreturn
                float                         switch                         _Static_assert
                for                           typedef                        _Thread_local
                goto                          union

Originally posted by @ztane in #2973 (comment)

[il3ven]

These keyword just need to be added in c.js? I was confirming before opening a PR.

[joshgoebel]

Well really someone with a larger knowledge of C could really help here. Hopefully a PR here will do more than just replace KEYWORDS#keyword. There are related connections also to:

• enh(cpp) Highlight all function dispatches #3005 (though eventually I'll get to this).
  • More important that we just get a correct list of built_in (ie, removing any cpp ones) for starters...
• Even the above keywords need to be split between keyword and type
• Review the rest of the syntax (for wrong modes like class and decltype, etc)

So that would be my hope here.

[joshgoebel]

@klmr Does modern C have namespaces?

[joshgoebel]

There is also begin: '\\b(deque|list|queue|priority_queue|pair|stack|vector|map|set|bitset|multiset|multimap|unordered_map|unordered_set|unordered_multiset|unordered_multimap|array)\\s*<', which I dunno if it applies to C as well as C++ or not.

[klmr]

No namespaces, no.

And that begin rule is pure C++, not C.

[joshgoebel]

What are _Bool and _Imaginary? Should we flag them as types?

[klmr]

They’re types, yes, but they’re also keywords (unlike e.g. bool, which in C is an alias for _Bool, but only if the stdbool.h header is included — otherwise it’s just any old identifier). https://en.cppreference.com/w/c/keyword is a good reference.

(Apologies for the lack of activity, I’m still snowed under with two other projects that unfortunately take priority and take up all my nominal “free time”.)