From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lndn.lancelotsix.com (vps-42846194.vps.ovh.net [IPv6:2001:41d0:801:2000::2400]) by sourceware.org (Postfix) with ESMTPS id F05693857804 for ; Sun, 28 Mar 2021 16:56:33 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org F05693857804 Received: from Plymouth (unknown [IPv6:2a02:390:9086:0:71e9:e8c4:8db9:e236]) by lndn.lancelotsix.com (Postfix) with ESMTPSA id BEC708182E; Sun, 28 Mar 2021 16:56:32 +0000 (UTC) Date: Sun, 28 Mar 2021 17:56:31 +0100 From: Lancelot SIX To: Simon Marchi Cc: gdb-patches@sourceware.org Subject: Re: [PATCH v3] [PR gdb/27614] gdb-add-index fails on symlinks. Message-ID: References: <20210327172758.30356-1-lsix@lancelotsix.com> <981b48ee-133a-7f06-9e5d-d1c331f360d1@polymtl.ca> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <981b48ee-133a-7f06-9e5d-d1c331f360d1@polymtl.ca> X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.11 (lndn.lancelotsix.com [0.0.0.0]); Sun, 28 Mar 2021 16:56:32 +0000 (UTC) X-Spam-Status: No, score=-5.1 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: gdb-patches@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gdb-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 28 Mar 2021 16:56:35 -0000 Le Sun, Mar 28, 2021 at 12:11:22PM -0400, Simon Marchi a écrit : > > > On 2021-03-27 1:27 p.m., Lancelot SIX via Gdb-patches wrote: > > Since V2: > > - Use GDB to follow symlink instead of readlink. Unlike > > readlink, GDB is guaranteed to be available. > > > > Since V1: > > - Replace '&>/dev/null' with '>/dev/null 2>&1' > > > > -- > > > > PR 27614 shows that gdb-add-index fails to generate the index when its > > argument is a symlink. > > > > The following one liner illustrates the reported problem: > > > > $ echo 'int main(){}'|gcc -g -x c -;ln -s a.out symlink;gdb-add-index symlink > > gdb-add-index: No index was created for symlink > > gdb-add-index: [Was there no debuginfo? Was there already an index?] > > $ ls -l > > -rwxr-xr-x 1 25712 Mar 19 23:05 a.out* > > -rw------- 1 8277 Mar 19 23:05 a.out.gdb-index > > lrwxrwxrwx 1 5 Mar 19 23:05 symlink -> a.out* > > > > GDB generates the .gdb-index file with a name that matches the name of > > the actual program (a.out.gdb-index here), not the symlink that > > references it. The remaining of the script is looking for a file named > > after the provided argument (would be 'symlink.gdb-index' in our > > example). > > > > The common option to solve such issue would be to use readlink to follow > > the symlink. Unfortunately, this command is not available in the POSIX > > standard. This commit therefore proposes to use GDB itself to identify > > where the symlink points to. This requires some parsing of GDB output. > > The added test should be enough to detect regression if GDB where to > > change the way it formats its output. > > I preferred your previous approach, compared to relying on a maintenance > command. Relying on a maintenance command is fine in tests, for example, > but here somebody could use gdb-add-index from a given GDB version with > a GDB of a different version. > > GDB=/my/newer/gdb gdb-add-index a.out Yes, agreed. I was reluctant to rely on maint command in the first place, I should have kept it that way! > > In the previous review, you said: > > >> Would it work with just `readlink `? > > > This would fail if $file is a symlink to a symlink. This is what > > ldconfig usually does (libfoo.so -> libfoo.so.x -> libfoo.so.x.y). > > Can't you just call it in a loop then? > > while file is a symlink: > file=readlink $file > Yes. It would look somethink like: if test -L "$1"; then if command -v readlink >/dev/null 2>&1; then file="$1" while test -L "$file"; do target=$(readlink "$file") case "$target" in /*) file="$target" ;; *) file="$(dirname "$file")/$target" ;; esac done else echo "$myname: 'readlink' missing. Failed to follow symlink $1." 1>&2 exit 1 fi else file="$1" fi I’ll test this and prepare a V4 shortly. Thanks for the comments. Lancelot. > Simon