From owner-svn-src-all@freebsd.org Thu May 5 16:45:22 2016 Return-Path: Delivered-To: svn-src-all@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id E0050B2E786; Thu, 5 May 2016 16:45:22 +0000 (UTC) (envelope-from asomers@gmail.com) Received: from mail-oi0-x244.google.com (mail-oi0-x244.google.com [IPv6:2607:f8b0:4003:c06::244]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id A40571BB1; Thu, 5 May 2016 16:45:22 +0000 (UTC) (envelope-from asomers@gmail.com) Received: by mail-oi0-x244.google.com with SMTP id f63so14836351oig.0; Thu, 05 May 2016 09:45:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:date:message-id:subject :from:to:cc; bh=w2BwrXxdcHJ6weLc/61irQfcktdm23opQYLfdu3doAQ=; b=GQC+d95/OPZiinZ1EroP/gVeOp2lnffk6Yj7ft+tfEzXCfbNaB2ffpnhkKmLN5J+EQ 8VqzpVPNqSpa5JR94waPvPjt+ObUUaSbjEiJ3X35XigjQBQWUrLajTdrvAjN4nq+pwgl CoevOcX0BOagtyH+aw2WsJtxLGcWaBWNg7+UrvsXlcF5Tf28kb7PxliFr3GjqU8GInUj gpccRPAkqtBMUYaxKMJZHTvZhLO3RRgwcEBYAF6MpmLg+qcPI9mcJHKEfV54KeiTnkTG hMj8C5vuGFSCd/xLVOhyzQksUIaJFYl7qX2tPSH4sN/z5+7hkycLvQDbzaDThRm/SBkv e7Iw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:sender:in-reply-to:references:date :message-id:subject:from:to:cc; bh=w2BwrXxdcHJ6weLc/61irQfcktdm23opQYLfdu3doAQ=; b=ZkTrcVBEAVrAxgCcJ5jy+8RZRFb9eI9UhhfgKy9OuRIbcU7cKqpJO5ExFytdriPLkG 7B5rxuJkVGQuB+oCWvZNNF55tZ6GzUbBYPKJiN+mvZzcDPRapvJcbRG+kbDZkAtbV8yP csiV+G/+PysnQQR5ykYL6yLQ1nRwPJ6uGaNOmfSqY0s9N9x5acLqBbYsbFONPmxfZjuZ BMKklGeqGbYQR+f3q9mFgvIFX/eDPLqzvChiDEvdx6xSldBVHoLo//FhgIB9kVXy676O /w7GGcubVAzSkNj36ntuOq6utPOko7zYYVMopZIN0UA+iqX/pD9fjHR0fs2Q3iFZaZo1 1ftQ== X-Gm-Message-State: AOPr4FX+Bbh6eNP4OBozkBjMZ06O8HKRpIxdzuWfXaa+XGizd6NI8FRDQAR2iMF+c0l5aadL3NT9NxKRVwpW6w== MIME-Version: 1.0 X-Received: by 10.202.64.132 with SMTP id n126mr6762549oia.80.1462466721674; Thu, 05 May 2016 09:45:21 -0700 (PDT) Sender: asomers@gmail.com Received: by 10.202.64.138 with HTTP; Thu, 5 May 2016 09:45:21 -0700 (PDT) In-Reply-To: <2368543.Vvp613SNcD@ralph.baldwin.cx> References: <201605042234.u44MYBMX054443@repo.freebsd.org> <2368543.Vvp613SNcD@ralph.baldwin.cx> Date: Thu, 5 May 2016 10:45:21 -0600 X-Google-Sender-Auth: PRs1MzPGxpYCkuR7jCV9nB-VUvs Message-ID: Subject: Re: svn commit: r299090 - in head: etc/mtree include lib/libbluetooth sbin/hastd share/man/man3 sys/dev/xen/blkback sys/kern sys/net sys/sys tests/sys tests/sys/sys usr.sbin/bluetooth/hccontrol From: Alan Somers To: John Baldwin Cc: "src-committers@freebsd.org" , "svn-src-all@freebsd.org" , "svn-src-head@freebsd.org" , Justin Gibbs Content-Type: text/plain; charset=UTF-8 X-Content-Filtered-By: Mailman/MimeDel 2.1.22 X-BeenThere: svn-src-all@freebsd.org X-Mailman-Version: 2.1.22 Precedence: list List-Id: "SVN commit messages for the entire src tree \(except for " user" and " projects" \)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 05 May 2016 16:45:23 -0000 On Thu, May 5, 2016 at 10:31 AM, John Baldwin wrote: > On Wednesday, May 04, 2016 10:34:11 PM Alan Somers wrote: > > Author: asomers > > Date: Wed May 4 22:34:11 2016 > > New Revision: 299090 > > URL: https://svnweb.freebsd.org/changeset/base/299090 > > > > Log: > > Improve performance and functionality of the bitstring(3) api > > > > Two new functions are provided, bit_ffs_at() and bit_ffc_at(), which > allow > > for efficient searching of set or cleared bits starting from any bit > offset > > within the bit string. > > > > Performance is improved by operating on longs instead of bytes and > using > > ffsl() for searches within a long. ffsl() is a compiler builtin in both > > clang and gcc for most architectures, converting what was a brute force > > while loop search into a couple of instructions. > > > > All of the bitstring(3) API continues to be contained in the header > file. > > Some of the functions are large enough that perhaps they should be > uninlined > > and moved to a library, but that is beyond the scope of this commit. > > Doesn't switching from bytes to longs break the ABI? That is, setting bit > 9 > now has a different representation on big-endian systems (0x00 0x01 before, > now 0x00 0x00 0x01 0x00 on 32-bit BE, and 4 more leading 0 bytes on > 64-bit). > This means you can't have an object file compiled against the old header > pass a bitstring to an object file compiled against the new header on > big-endian > systems. > > Even on little-endian systems if an old object file allocates storage for a > bitstring the new code might read off the end of it and fault (or return > garbage if bits are set in the extra bytes it reads off the end)? > > Is the API is so little used we don't care? > > -- > John Baldwin > The API isn't used in any shared libraries, so the only risk would be if it's used in a user application where the user's build system doesn't check for changes in system libraries, and the user upgrades FreeBSD without doing a clean build of his application, right? Am I missing any other scenarios? Do we need to warn users with a line in UPDATING or something? This is similar to an upgrade of the C++ compiler. C++ objects built by different minor versions of the compiler aren't guaranteed to be compatible. -Alan