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Re: Switching to C++ by default in 4.8
On Tue, Apr 10, 2012 at 9:39 AM, Jakub Jelinek <jakub@redhat.com> wrote:
> On Tue, Apr 10, 2012 at 09:22:56AM -0700, Xinliang David Li wrote:
>> On Tue, Apr 10, 2012 at 1:46 AM, Jakub Jelinek <jakub@redhat.com> wrote:
>> > On Mon, Apr 09, 2012 at 04:34:32PM -0700, Xinliang David Li wrote:
>> >> Class hierarchy is one such feature that is useful. Assuming we have
>> >> two hierarchies for gcc: one for values rooted at ValExp, and one for
>> >> gimple stmts rooted at GimpInst.
>> >>
>> >> 1) For IR browsing,
>> >> ? ?*) all the macro accessors can be eliminated -- a big plus for debugging;
>> >
>> > Not that clear, if all the macros are replaced by tons of inline functions,
>> > the debugging experience can be actually significantly worse. ?Already some the
>> > inline functions used like tree_operand_length used by TREE_OPERAND_LENGTH
>> > macro are extremely annoying from debugging POV.
>>
>> What is the root cause of the annoyance? Mixing macros and inline
>> functions does not sound good, but using deeply nested macros do not
>> seem to help the debugging situation either.
>
> That when stepping through code in the debugger you keep enterring/exiting
> these one liner inlines, most of them really should be at least by default
> considered just as normal statements (e.g. glibc heavily uses artificial
> attribute for those, still gdb doesn't hide those by default).
>
>> > Not to mention it is very questionable if the above stuff is more readable
>> > than what we currently have.
>>
>> The above is just quickly cooked up examples. A carefully designed C++
>> based API can be self documenting and make the client code very
>> readable. It is hard to believe that there is no room for improvement
>> in GCC.
>
> Do you have examples? ?E.g. I haven't touched gold, because, while it is a new
> C++ codebase, looks completely unreadable to me, similarly libdw C++ stuff.
> A carefully designed C based API can be self documenting and make the code
> very readable as well, often more so.
Personally I think the core APIs should be abstract enough to hide IR
details, and high level (possibly multi-level) to allow efficient code
manipulation -- be it C or C++. However I think this is really more
about the general perceptions and how future developers feel about it.
thanks,
David
>
> ? ? ? ?Jakub