cmpfuncs

#!/usr/bin/env bash
#
# cmpfuncs
#   - compares all functions that exist in both source files $1 and $2
#   - any remaining args restrict comparison to only those function names
#   - system must support "ctags -x" (ie exuberant, universal)
#   - outputs universal diff hunks for each differing function, or nothing
#   - function signature line (the ctags referent line) is not compared
#   - functions must end on a line with trailing brace in column 0
#   - only tested with C files
#
# scott@smemsh.net
# https://github.com/smemsh/utilsh/
# https://spdx.org/licenses/GPL-2.0
#

for f in ${1:?} ${2:?}
do test -f $f -a -r $f || exit; done

if (($# > 2)); then
	declare -A onlyfuncs
	for f in ${@:3}; do onlyfuncs[$f]=1; done
fi

printfuncs ()
{
	ctags -x ${1:?} \
	| awk '$2 == "function" {print $1, $3}'
}

displayfunc ()
{
	echo "$sigline" # always use file2's signature line
	tail -n +$(($2 + 1)) $1 | grep -m1 -B999 '^}'
}

eval declare -A funcs1=($(printfuncs $1))
eval declare -A funcs2=($(printfuncs $2))

for func in ${!funcs1[@]}
do
	loc1=${funcs1[$func]}
	loc2=${funcs2[$func]}
	[[ $loc2 ]] || continue
	((${onlyfuncs[$func]})) || continue

	declare -x sigline="$(sed -n ${loc2}p $2)"
	diffout="$(diff -pwu <(displayfunc $1 $loc1) <(displayfunc $2 $loc2))"
	if [[ ${diffout:+x} ]]; then
		sed -r \
		-e "/^-{3}/s,/dev/fd/.*\\>,$1," \
		-e "/^\\+{3}/s,/dev/fd/.*\\>,$2," \
		<<< "$diffout"
		echo
	fi
done