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Re: [PATCH] manage dom-walk_data initialization and finalization with constructors and destructors
- From: Trevor Saunders <tsaunders at mozilla dot com>
- To: Michael Matz <matz at suse dot de>
- Cc: Jeff Law <law at redhat dot com>, Richard Biener <richard dot guenther at gmail dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>
- Date: Thu, 19 Sep 2013 13:24:49 -0400
- Subject: Re: [PATCH] manage dom-walk_data initialization and finalization with constructors and destructors
- Authentication-results: sourceware.org; auth=none
- References: <20130904145911 dot GC17620 at tsaunders-iceball dot corp dot tor1 dot mozilla dot com> <522759C8 dot 5040802 at redhat dot com> <20130911000350 dot GA28492 at tsaunders-iceball dot corp dot tor1 dot mozilla dot com> <52389CB1 dot 60504 at redhat dot com> <5239126A dot 6010702 at redhat dot com> <alpine dot LNX dot 2 dot 00 dot 1309181640400 dot 9949 at wotan dot suse dot de> <5239D985 dot 4080205 at redhat dot com> <alpine dot LNX dot 2 dot 00 dot 1309181849550 dot 9949 at wotan dot suse dot de> <523A7C15 dot 60508 at redhat dot com> <alpine dot LNX dot 2 dot 00 dot 1309191452590 dot 9949 at wotan dot suse dot de>
On Thu, Sep 19, 2013 at 03:23:21PM +0200, Michael Matz wrote:
> > I don't see anything in Trevor's work that requires jumping through
> > hoops.
> Me neither, from that perspective it's okay. It's merely that I doubt the
> value of any syntactic privatization like it's implemented in C++, you can
> #define it away, hence the compiler can't make use of that information for
no, it can't make use of it if someone does something crazy like #define
it away which is atleast a little tricky because of the ':'. I believe
clang does infact make use of private to find unused fields (maybe it
does something else, but I can't imagine what that would be).
> code generation, and the cognitive value for the developer ("hey I
> shouldn't look at this member from outside") is dubious, as that probably
> is a general rule, no direct data member access from non-members (although
> I have problems with that too).
The value is that when you read code you *know* that something is only
used in certain places instead of hoping that is true.
> And I think the fact that Trevor made one data member non-private to
> access it from a non-member function (move_computations_dom_walker::todo)
> just underlines my point: private is useless and gets in the way.
It certainly shows a case where that's true, but it doesn't really show
that's always true.
> > > What's the benefit of reading and writing such noisy lines? :
> > >
> > > *out_mode = mode_;
> > > mode_ = GET_MODE_WIDER_MODE (mode_);
> > > count_++;
> > It makes it very clear to the reader that we're dealing with objects that
> > belong to a class instance rather than direct access to an auto or static.
> > That can be important.
> From the wiki it seems that was dicussed (on the wiki, not the mailing
> list) and rejected by Lawrence on the grounds of indroducing too long
> lines. I agree with that, but I don't agree that therefore members should
> be named foo_.
this-> also has the disadvantage that you always have to rember it, and
fundimentally doesn't help you know where a member could possibly be
> > Given it's recommended by our C++ guidelines which were discussed at
> > length, I'm going to explicitly NAK your patch.
> > FWIW, I have worked on large C++ codebases
> Me too.
> > that were a free-for-all and found them *amazingly* painful.
> I don't think any of my mails about style can be interpreted as advocating
> > The restricted set allowed for GCC is actually quite reasonable IMHO,
> > particularly for projects where the main body of code is evolving from a
> > pure C base.
> Funnily it's the small things that weren't much discussed (probably
> because they are deemed not very important) in the convention that give
> me a hard time, nits such as these syntactic uglifications. The larger
> things indeed mostly are okayish.