Re: Merge cpplib and front end hashtables, part 1

[Neil Booth <neil at daikokuya dot demon dot co dot uk>]

Neil Booth wrote:-

> Scrap this.  I've got a better idea.  You give cpplib some text you
> want macro expanded.  You don't give cpplib any macro definitions, but
> instead give it a callback where it enquires whether a macro is
> defined at that location in the source file.  GDB does it's stuff to
> figure that out, which I imagine is pretty easy and fast.
> 
> If so, your callback routine calls cpp_define () with the macro
> definition, and returns to cpplib, which continues to try to expand
> the macro expression.
> 
> This way, we can do lazy insertion of macros and be very efficient
> about it, and fully free them all after the one expansion.  Yeah!
> However, this callback check would get in cpplib's fast path I think;
> we'd need to be careful we don't penalize GCC to a noticable extent to
> benefit GDB.

The more I think about this, the more I like it.  It'd only be a
couple of lines in cpp_get_token, which we could conditionally compile
in a #ifdef ... #endif so as not to hurt GCC, and one or two in
another place to give you a way to flush macro memory, and that'd be
it.  I'll try and knock something up in the next day or so.

Cheers,

Neil.