From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-3.7 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_HI, RCVD_IN_SORBS_SPAM,RP_MATCHES_RCVD shortcircuit=no autolearn=no autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 69D8720196 for ; Mon, 8 May 2017 22:06:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751018AbdEHWG5 (ORCPT ); Mon, 8 May 2017 18:06:57 -0400 Received: from mail-pf0-f169.google.com ([209.85.192.169]:36365 "EHLO mail-pf0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750808AbdEHWG4 (ORCPT ); Mon, 8 May 2017 18:06:56 -0400 Received: by mail-pf0-f169.google.com with SMTP id m17so10112487pfg.3 for ; Mon, 08 May 2017 15:06:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc; bh=/IHVQG/P69+vUmoSYEHXtpC5WBReH15FOD4+IJQx5Ig=; b=uyjJgLdc5ZKzVXB3kM6OiSYagFPHjT2zkjMxYhY2zCx9qAGuj4sy584hlvxkdZ6fhq q8zp39qY8wODILWyynQwAmf69xp9wX4qO9rFmikBJFWe0WE3Z+3pvqciHeoSp8ftiXdh kUg29DiXqT5QRF1aE+opVHuu0Ceaf/2YFqigk6SHURUAGt9V5DrrAY5AOUci4JCOAm1C eluaC2QtKRzNH+CP7wLG3hvYPnJi3sZc2cuFeQ6BLbFlFU3i5O/b/xHbdXG21J+U4RQQ ZGfaZKTEVRjdkrza1d8ft7AQyXkODGLmrB2IEA2TFypzlJhn9xOC9+Yz0v61xYjVIQYh LVBA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=/IHVQG/P69+vUmoSYEHXtpC5WBReH15FOD4+IJQx5Ig=; b=o5JeF3JNG7JxD+Fo9ZoZbYSW62aKySrxlj6v9+T+lj3YKq9X+lpUZThq7nsluPunXI pYp35NKLeVU3sGCIbrUrcdVyUJY6ojHDydhc3KXYuPvlGI73niDY3jcSblotyGIlgEjz 8dM+nEPIKnfaaQPR2Tv0IyPvJe94ez+4nsao3def/GnQoql+qH2myIeHyOCbGtMizYSk FcmOtcF1th2oKr74oE82O7SyKYaVHvKT3xW3psJeFpL9zoE1F4U4h56p6W+D65sqXqhm zPPZcJB9VYkLzQJVluqUTrtW/maeiz3SCozioC8wKpPr15nQoGPJi5PcxPU37Uj7lSXY 9YVw== X-Gm-Message-State: AN3rC/6/aIITJ7ryJ1reNgoGZSXKrdY83DK2N1JJpA9aAxtO9RfS+xGl cf1QDnadC7XOj4ITnJ74g9MvO1YKEmZk X-Received: by 10.99.56.66 with SMTP id h2mr21266516pgn.40.1494281215169; Mon, 08 May 2017 15:06:55 -0700 (PDT) MIME-Version: 1.0 Received: by 10.100.162.140 with HTTP; Mon, 8 May 2017 15:06:54 -0700 (PDT) In-Reply-To: <20170508215525.gcyzzntqvm52mqcc@sigill.intra.peff.net> References: <20170505052729.7576-1-whydoubt@gmail.com> <20170505052729.7576-3-whydoubt@gmail.com> <20170508215525.gcyzzntqvm52mqcc@sigill.intra.peff.net> From: Stefan Beller Date: Mon, 8 May 2017 15:06:54 -0700 Message-ID: Subject: Re: [RFC PATCH 02/10] Move textconv_object to be with other textconv methods To: Jeff King Cc: Junio C Hamano , Jeff Smith , "git@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Mon, May 8, 2017 at 2:55 PM, Jeff King wrote: > On Mon, May 08, 2017 at 10:02:58AM +0900, Junio C Hamano wrote: > >> Stefan Beller writes: >> >> > I guess it is ok for now and in this series, but we may want >> > to split up diff.[ch] in the future into multiple finer grained files. >> >> For what end? Such a split would require more symbols internal to >> diff.[ch] to become external, which is a big downside, so we need to >> have a large reward to compensate it if we were to go there. > > I think there are two sides to that coin. Let's say you have a file with > five functions (and you can replace function with structs, global > variables, etc; any unit of complexity that might or might not be > externally visible): > > /* called by both a() and b() */ > static void a_and_b_helper(); > > /* called by a() */ > static void a_helper(); > void a(); > > /* called by b() */ > static void b_helper(); > void b(); > > When they are in the same file, b() and b_helper() can see a_helper(), > even though they don't need it. And that means increased complexity in > dealing with a_helper(), because its visibility is larger than > necessary. We have to worry about what a change to it might do to b() > (or more realistically, c(), d(), etc). > > If we split this apart, we end up with three files: > > common.c: > void a_and_b_helper(); > > a.c: > static void a_helper(); > void a(); > > b.c: > static void b_helper(); > void b(); > > The specific helpers have less visibility, which is good. The public > functions a() and b() were already public, so no change. But now the > common helper is public, too, even though nobody except a() and b() care > about it. > > So it's a tradeoff. And the important question is: is the bleed-over > between a() and b() worse than the common bits being made public? That > can't be answered without looking at how many distinct "a" and "b"-like > chunks there are in the file, and what the common bits look like. I'm > not sure of the answer for diff.c. Without digging, both ends of the > spectrum seem equally plausible to me: that it is mostly a set of N > distinct units which could be split apart, or that it really is a few > public functions calling the same common core over and over. > > And a follow-on question is what we can do to mitigate the cost of > making the common code public. We could advertise a_and_b_helper() only > in diff-internal.h, and then makes it only semi-public (anybody can > include that, of course, but including diff-internal.h seems like it > ought to be a red flag). That only helps the programmer, though; we'd > still be losing out on compiler optimizations and static analysis that > only looks at one translation unit at a time. > > Phew. That ended up a little long-winded. All of it is to say that I > don't think it makes sense to reject a split out-of-hand, but nor is it > always a good thing. It depends on what's in the file. I agree on this sentiment. It really depends on the content under discussion whether it makes sense to split. Having had some exposure recently for diff.[ch] (and I just picked up that series again, but did not send it out yet), I have the impression that we do have a lot of code in diff.c, which is quite unrelated to each other, i.e. a lot of [a,b]_helper()s, and few a_and_b_helper() for the already public functions. May first mail was based on perceived unneeded complexity, which slows down in achieving a goal. Thanks, Stefan