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nixpkgs/pkgs/build-support/setup-hooks/separate-debug-info.sh
Eelco Dolstra 2fcee55e5f separateDebugInfo: Create symlinks matching original binaries
For instance, a binary like libfoo.so will cause a symlink
lib/debug/libfoo.so.debug -> .build-id/<build-ID>.debug to be
created. This is primarily useful for use with eu-addr2line, if you
know the name of a binary and the relative address, but not the build
ID.
2016-01-15 16:16:11 +01:00

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export NIX_LDFLAGS+=" --build-id"
export NIX_CFLAGS_COMPILE+=" -ggdb"
dontStrip=1
fixupOutputHooks+=(_separateDebugInfo)
_separateDebugInfo() {
local dst="${debug:-$out}"
if [ "$prefix" = "$dst" ]; then return; fi
dst="$dst/lib/debug/.build-id"
# Find executables and dynamic libraries.
local -a files=($(find "$prefix" -type f -a \( -perm /0100 -o -name "*.so" -o -name "*.so.*" \)))
local i magic
for i in "${files[@]}"; do
# Skip non-ELF files.
exec 10< "$i"
read -n 4 -u 10 magic
exec 10<&-
# Extract the Build ID. FIXME: there's probably a cleaner way.
local id="$(readelf -n "$i" | sed 's/.*Build ID: \([0-9a-f]*\).*/\1/; t; d')"
if [ "${#id}" != 40 ]; then
echo "could not find build ID of $i, skipping" >&2
continue
fi
# Extract the debug info.
header "separating debug info from $i (build ID $id)"
mkdir -p "$dst/${id:0:2}"
objcopy --only-keep-debug "$i" "$dst/${id:0:2}/${id:2}.debug" --compress-debug-sections
strip --strip-debug "$i"
# Also a create a symlink <original-name>.debug.
ln -sfn ".build-id/${id:0:2}/${id:2}.debug" "$dst/../$(basename "$i")"
done
}
# - We might prefer to compress the debug info during link-time already,
# but our ld doesn't support --compress-debug-sections=zlib (yet).
# - Debug info may cause problems due to excessive memory usage during linking.
# Using -Wa,--compress-debug-sections should help with that;
# further interesting information: https://gcc.gnu.org/wiki/DebugFission
# - Another related tool: https://fedoraproject.org/wiki/Features/DwarfCompressor