#! /bin/bash

display_help()
{
echo -e "
Usage: lto-rebuild [OPTION]

lto-rebuild can be used to avoid a full system rebuild after upgrading GCC
when using GentooLTO. It searches in /usr/lib, /usr/lib32, and /usr/lib64
on your system for all installed static archives that were built using
a different GCC than the current one.

Note: make sure your system is as up to date as possible before doing this.
If an installed package does not have a corresponding ebuild available,
this command will fail. You can use -l to manually intervene.

Options:

-h	Display this help
-a	Only list the archives that were built with other GCC versions
-l	Only list the packages that would be rebuilt (and their slots)
-r	Rebuild the packages using emerge (will ask for confirmation)
"
}

perform_action()
{
local prefix="${EROOT%/}/usr/lib"
local suffix="\.a"
local archives=()
local packages=()
local GCC_VER=""

GCC_VER=$(gcc -dumpversion)

echo -e "Searching in
	${prefix}
	${prefix}64
	${prefix}32
for static archives that were built using a different GCC...\n" >&2

# Exclude /usr/lib/gcc/<arch> because these are internal
# to the [cross-]compilers on the system
mapfile -t archives < <(
	find "${prefix}"{,64,32} -type f -name "*${suffix}" \
	-exec readelf -p .comment {} + \
	-o -path "${prefix}64/gcc" -prune \
	-o -path "${prefix}32/gcc" -prune \
	-o -path "${prefix}/gcc" -prune 2> /dev/null | \
	grep -v "${GCC_VER}" | grep -B3 "GCC:" | \
	grep -o "${prefix}.*${suffix}" | uniq
)

if [[ ${#archives[@]} -eq 0 ]]
then
	echo "No problems found!" >&2
	exit 0
fi

if [[ "${1}" != "-a" ]]
then
	mapfile -t packages < <(qfile -qS "${archives[@]}" | sort -u)
fi

case "${1}" in
	"-a")
		echo "The following static archives were built" >&2
		echo -e "using a different GCC:\n" >&2
		printf "%s\n" "${archives[@]}"
		;;
	"-l")
		echo "The following packages installed static archives" >&2
		echo -e "that were built using a different GCC:\n" >&2 
		printf "%s\n" "${packages[@]}"
		;;
	"-r")
		emerge -1a "${packages[@]}"
		;;
	*)
		exit 1
		;;
esac
}

case "${1}" in
	"" | "-h")
		display_help
		;;
	"-l" | "-a" | "-r")
		perform_action "${1}"
		;;
	*)
		exit 1
		;;
esac