Note before you read the rest: The shell script shown here is certainly not safe to use and well tested. Use at your own risk!
I wrote a bash script to accomplish that task. Suppose your library is lib1 and the one you need to include some symbols from is lib2. The script now runs in a loop, where it first checks which undefined symbols from lib1 can be found in lib2. It then extracts the corresponding object files from lib2 with ar, renames them a bit, and puts them into lib1. Now there may be more missing symbols, because the stuff you included from lib2 needs other stuff from lib2, which we haven't included yet, so the loop needs to run again. If after some passes of the loop there are no changes anymore, i.e. no object files from lib2 added to lib1, the loop can stop.
Note, that the included symbols are still reported as undefined by nm, so I'm keeping track of the object files, that were added to lib1, themselves, in order to determine whether the loop can be stopped.
#! /bin/bash
lib1="$1"
lib2="$2"
if [ ! -e $lib1.backup ]; then
echo backing up
cp $lib1 $lib1.backup
fi
remove_later=""
new_tmp_file() {
file=$(mktemp)
remove_later="$remove_later $file"
eval $1=$file
}
remove_tmp_files() {
rm $remove_later
}
trap remove_tmp_files EXIT
find_symbols() {
nm $1 $2 | cut -c20- | sort | uniq
}
new_tmp_file lib2symbols
new_tmp_file currsymbols
nm $lib2 -s --defined-only > $lib2symbols
prefix="xyz_import_"
pass=0
while true; do
((pass++))
echo "Starting pass #$pass"
curr=$lib1
find_symbols $curr "--undefined-only" > $currsymbols
changed=0
for sym in $(cat $currsymbols); do
for obj in $(egrep "^$sym in .*\.o" $lib2symbols | cut -d" " -f3); do
echo " Found $sym in $obj."
if [ -e "$prefix$obj" ]; then continue; fi
echo " -> Adding $obj to $lib1"
ar x $lib2 $obj
mv $obj "$prefix$obj"
ar -r -s $lib1 "$prefix$obj"
remove_later="$remove_later $prefix$obj"
((changed=changed+1))
done
done
echo "Found $changed changes in pass #$pass"
if [[ $changed == 0 ]]; then break; fi
done
I named that script libcomp, so you can call it then e.g. with
./libcomp libmylib.a libwhatever.a
where libwhatever is where you want to include symbols from. However, I think it's safest to copy everything into a separate directory first. I wouldn't trust my script so much (however, it worked for me; I could include libgsl.a into my numerics library with that and leave out that -lgsl compiler switch).
