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Re: RFC: C/C++ preprocessor macro support for GDB
- From: Neil Booth <neil at daikokuya dot demon dot co dot uk>
- To: Jim Blandy <jimb at redhat dot com>
- Cc: gdb-patches at sources dot redhat dot com, gcc at gcc dot gnu dot org
- Date: Mon, 18 Mar 2002 18:33:39 +0000
- Subject: Re: RFC: C/C++ preprocessor macro support for GDB
- References: <20020317062306.CC96D5E9DE@zwingli.cygnus.com>
Jim Blandy wrote:-
>
> The following patch adds support for C/C++ preprocessor macros to GDB.
> It's tentative:
>
> - There are no ChangeLog entries.
> - It's not broken up into relatively independent changes.
> - There's no documentation.
> - There are no tests.
> - There are some unimplemented features.
>
Jim,
I've looked over your patch a little more, and I don't think your macro
expander works, because it doesn't mark individual tokens. A "disabled
macro" stack is *not* enough by itself to implement ISO C macro expansion
semantics. You need to attach information to individual tokens as well.
I've not tried it, but I'd bet that
#define A(x) x A(A)(1)
expands to "1" with your code, whereas the correct expansion is "A(1)".
Implementing this properly is a PITA, more so with a text-based expander
like yours. It would be very hard to get the same (correct) semantics as
cpplib in corner cases with a text-based expander (2.95 has outstanding
bugs in this area).
In addition, as you note #, ## and the various variadic macro semantics
and GCC extensions have not been implemented, I think a lot of work lies
ahead in this implementation. IMO using cpplib will be a lot less effort,
even after what you've already accomplished.
Neil.