Re: [PATCH v3] Resurrect gdb-add-index as a contrib script

[Doug Evans <dje at google dot com>]

On Sun, Nov 3, 2013 at 1:57 PM, Samuel Bronson <naesten@gmail.com> wrote:
> This includes some changes made in Fedora's gdb packaging[1], and
> Doug's robustness patch[2] from before it was dropped (with some
> slight corrections).
>
> [1]: http://pkgs.fedoraproject.org/cgit/gdb.git/log/gdb-gdb-add-index-script.patch?id=fe74423b0812bae6d7bb027584e401a2ac37d24d
> [2]: https://sourceware.org/ml/gdb-patches/2010-09/msg00130.html
>
> I'm including a log of relevant previous activity.
>
> (I would just include committishes, but I'm not quite confident that
> history won't be rewritten again, invalidating the hashes, plus there
> are no relevant tags so the first two parts of git-describe(1) output
> wouldn't be any help either.)
>
> [...]
> diff --git a/gdb/ChangeLog b/gdb/ChangeLog
> index 79abe3d..def36a3 100644
> --- a/gdb/ChangeLog
> +++ b/gdb/ChangeLog
> @@ -1,3 +1,11 @@
> +2013-11-08  Tom Tromey  <tromey@redhat.com>
> +           Jan Kratochvil <jan.kratochvil@redhat.com>
> +           Doug Evans <dje@google.com>
> +           Samuel Bronson  <naesten@gmail.com>
> +
> +       Bring back gdb-add-index as a contrib script.
> +       * contrib/gdb-add-index.sh: New file.
> +
>  2013-11-08  Doug Evans  <dje@google.com>

I think this deserves a NEWS entry.

>         * dwarf2read.c (dwarf2_read_debug): Change to unsigned int.
> diff --git a/gdb/contrib/gdb-add-index.sh b/gdb/contrib/gdb-add-index.sh
> new file mode 100755
> index 0000000..437e8c4
> --- /dev/null
> +++ b/gdb/contrib/gdb-add-index.sh
> @@ -0,0 +1,61 @@
> +#! /bin/sh
> +
> +# Add a .gdb_index section to a file.
> +
> +# Copyright (C) 2010, 2012-2013 Free Software Foundation, Inc.
> +# This program is free software; you can redistribute it and/or modify
> +# it under the terms of the GNU General Public License as published by
> +# the Free Software Foundation; either version 3 of the License, or
> +# (at your option) any later version.
> +#
> +# This program is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +# GNU General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
> +
> +# This program assumes gdb and objcopy are in $PATH.

In my local copy I added the ability to specify which gdb to use,
useful when using a test gdb.
I never needed to specify objcopy, but for consistency's sake ...

GDB=${GDB:=gdb}
OBJCOPY=${OBJCOPY:=objcopy}

or some such?

> +
> +myname="${0##*/}"
> +
> +if test $# != 1; then
> +    echo "usage: $myname FILE" 1>&2
> +    exit 1
> +fi
> +
> +file="$1"
> +
> +if test ! -r "$file"; then
> +    echo "$myname: unable to access: $file" 1>&2
> +    exit 1
> +fi
> +
> +dir="${file%/*}"
> +test "$dir" = "$file" && dir="."
> +index="${file}.gdb-index"
> +
> +# Ensure intermediate index file is removed when we exit.
> +trap "rm -f $index" 0
> +
> +gdb --batch-silent -nx -iex 'set auto-load no' \
> +    -ex "file $file" -ex "save gdb-index $dir" || {
> +    # Just in case.
> +    status=$?
> +    echo "$myname: gdb error generating index" 1>&2
> +    exit $status
> +}
> +
> +# In some situations gdb can exit without creating an index.  This is
> +# not an error.
> +# E.g., if $file is stripped.  This behaviour is akin to stripping an
> +# already stripped binary, it's a no-op.

status=0

> +
> +if test -f "$index"; then
> +    objcopy --add-section .gdb_index="$index" \
> +       --set-section-flags .gdb_index=readonly "$file" "$file"
> +    status=$?

Another thing I added is a message here that no index was generated,
rather than a "silent failure".
[Not always a "failure", but helpful to know regardless.]

else
    echo "No index generated.  This is not necessarily a bug."
    echo "[E.g., Was $file built in debug mode?]"

I don't have a strong opinion on adding this, but I have found it useful.

> +fi
> +
> +exit $status