what are exactly GCC core types?

[Basile Starynkevitch <basile at starynkevitch dot net>]

Hello,

What are exactly GCC code types, defined in gcc/coretypes.h?

Of course, they are very important types used in GCC. And there are
probably wired in gengtype (but maybe not all of them; I didn't check
for all; certainly gengtype handle tree & gimple specially in some
way.).

However, I don't understand why gimple_seq_node is a core type. It seems
rarely used (outside of gimple*.[ch] files), and I would imagine it
could be kept in gimple.h.

I also don't understand why 
  union section;
  typedef union section section;
  struct cl_target_option;
  struct cl_optimization;
should be kept in gcc/coretypes.h


I could imagine that the transition to C++ might have to C++-ify these
core types (all of gcc/coretypes.h) very quickly, or on the contrary to
keep them as they are, without making a class of them, for a long time.

Do we have a clear criterium to add, keep, or remove a type from
gcc/coretypes.h?

Regards.

-- 
Basile STARYNKEVITCH         http://starynkevitch.net/Basile/
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