Generating symbols files from a series of .deb files

Christoph Berg

December 27, 2011

PostgreSQL’s libpq5 package got its symbols file somewhere around version 8.4, so the symbols in there were all marked with version “8.4~” or greater. As I’m working on pgapt.debian.net aiming at providing packages for all upstream-supported PG versions (currently 8.3 and up), this made packages incompatible with 8.3’s libpq5.

There didn’t seem to be a ready program to feed a series of .deb files which would then run dpkg-gensymbols and build a symbols file, so I wrote this shell script:

#!/bin/sh

set -eu

[ -d tmp ] || mkdir tmp

i=1

for pkg in "$@" ; do
	echo "$pkg"
	test -e "$pkg"
	name=$(dpkg-deb -I "$pkg" | perl -lne 'print $1 if /^ Package: (.+)/')
	version=$(dpkg-deb -I "$pkg" | perl -lne 'print $1 if /^ Version: (.+)/')
	out=$(printf "tmp/%03d_%s" $i "$version")
	dpkg-deb -x "$pkg" "$out"
	dpkg-gensymbols -P"$out" -p"$name" -v"$version" \
		${oldsymbols:+-I"$oldsymbols"} -O"$out.symbols" | \
		tee "$out.symbols.diff"
	test -s "$out.symbols.diff" || rm "$out.symbols.diff"
	oldsymbols="$out.symbols"
	rm -rf "$out"
	i=$(expr $i + 1)
done

To use it, do the following:

debsnap -a i386 libpq5
ls binary-libpq5/*.deb > files
edit "files" to have proper ordering (~rc versions before releases, remove bpo versions, etc.)
./walk-symbols $(cat files)

The highest-numbered *.symbols file in tmp/ will then have symbol information for all packages. I then did some manual post-processing like s/~~rc1-1/~~/ to get nice (and backportable) version numbers.

Another nice trick (pointed out by jcristau) is to replace the lowest version number of that package (8.2~ here, where libpq changed SONAME) by 0 which will make dpkg-shlibdeps omit the >= version part. (Most packages depending on libpq5 will profit from that.)

I’m still pondering whether this script is non-trivial enough add to devscripts. (The people I asked so far only made comments about the mkdir call…)

Debian