A quick bash script that tries to generate shims to allow Mach-O objects to link to assembly written for ELF objects.

mach-mangle-shim.sh

 #!/usr/bin/env bash
export CLANG_FORCE_COLOR_DIAGNOSTICS=0
SYMBOLS=()
OBJECTS=()

# Check for OSX.
if [[ "$(uname -s)" != "Darwin" ]]; then
	printf "\x1B[31m%s\x1B[0m\n" "Mach-O demangle shim isn't needed on non-Darwin platforms."
	exit 0
fi

# Determine the object files.
for file in *.s *.c; do
	if [[ "$file" = "__shim.s" ]]; then continue; fi
	OBJECTS+=("$(basename "$(basename "$file" .s)" .c)".o)
done

# Make the object files.
printf "Compiling objects...\n\x1B[2m"
COLOR=false make clean
COLOR=false make "${OBJECTS[@]}" 2>/dev/null
printf "\x1B[0m"

# Extract symbols from the object files.
printf "Extracting symbols...\n\x1B[2m"
for obj in *.o; do
	while read -r encounter symbol; do
		if [[ "$encounter" = "G" ]] && ! [[ "$symbol" =~ ^_ ]]; then
			SYMBOLS+=("$symbol")
			printf "%-30s %s\n" "$symbol" "[requires mangle]"
		fi
	done < <(objdump -t "$obj" | awk '
		/ g / && !/__DATA/ { print "G "$NF }
		/\*UND\*/ { print "U "$NF }
	')
done
printf "\x1B[0m"

# Generate shim.
printf "Generating shim...\n\x1B[2m"
{
	for symbol in "${SYMBOLS[@]}"; do
		echo ".globl _$symbol"
		echo "_$symbol: jmp $symbol"
	done
} > "__shim.s"
cat __shim.s
printf "\x1B[0m"

# Patch makefile.
printf "Patching makefile...\n\x1B[2m"
if ! grep '__shim.s' < makefile &>/dev/null; then
	echo "Finding targets..."
	TARGETS=($(grep 'all:' < makefile | sed 's/^all://'))
	if [[ -z "${TARGETS[*]}" ]]; then
		printf "\x1B[31mFailed to patch makefile.\x1B[0m\n"
		exit 1
	fi

	for target in "${TARGETS[@]}"; do
		printf "Patching '%s'... " "$target"

		found=false
		while IFS='' read -r line; do
			if ! $found; then
				if ! grep "^$target:" <<< "$line" &>/dev/null; then
					echo "$line"
					continue;
				fi
				
				echo "$line __shim.s"
				found=true;
				continue
			fi

			if grep "^\s*gcc " <<< "$line" &>/dev/null; then
				echo "$line __shim.s"
				echo "OK" >&2
				cat
				
				mv makefile.tmp makefile
				continue 2;
			fi
		done < makefile > makefile.tmp
		
		# Couldn't automatically patch it.
		printf "\x1B[31mFailed to patch makefile.\x1B[0m\n"
		exit 1
	done 2>&1
fi
printf "\x1B[0m"

# Done!
printf "\x1B[32mDone!\x1B[0m\n"