Error in Makefile calling sed with comment character - sed

Question

I'm trying to build lstrip, a Lua utility for compressing Lua source code. I'm trying to build for Lua 5.1.3 on OS X v10.10.3.
I have downloaded and extracted the Lua 5.1.3 source code and modified the Makefile for lstrip to point to this directory. However, when I run make, I get this output:
cc -I/usr/local/src/lua-5.1.3/src -I/usr/local/src/lua-5.1.3/src -O2 -Wall -Wextra -O2 -c -o lstrip.o lstrip.c
lstrip.c:33:14: warning: unused parameter 'argc' [-Wunused-parameter]
int main(int argc, char* argv[])
^
1 warning generated.
sed '/void luaX_next/i#include "proxy.c"' /usr/local/src/lua-5.1.3/src/llex.c > llex.c
sed: 1: "/void luaX_next/i#inclu ...": command i expects \ followed by text
make: *** [llex.c] Error 1
This is what the relevant Makefile command looks like:
llex.c:
sed '/void luaX_next/i#include "proxy.c"' $(LUASRC)/$# > $#
I think that this is because the # in the sed command is being treated like an actual comment, but I'm not sure.
How can I fix the Makefile, or manually run the steps, to get lstrip built?
Full copy of the Makefile follows, in case it matters:
# makefile for lstrip
# change these to reflect your Lua installation (Lua 5.1!)
LUA= /usr/local/src/lua-5.1.3
LUAINC= $(LUA)/src
LUALIB= $(LUA)/src
LUASRC= $(LUA)/src
# no need to change anything below here
CFLAGS= $(INCS) $(WARN) -O2 $G
WARN= -O2 -Wall -Wextra
INCS= -I$(LUAINC) -I$(LUASRC)
LIBS= -L$(LUALIB) -llua -lm
MYNAME= lstrip
MYLIB= $(MYNAME)
T= $(MYNAME)
OBJS= $(MYNAME).o llex.o
TEST= test.lua
all: test
test: $T
$T $(TEST)
$T: $(OBJS)
$(CC) -o $# $(OBJS) $(LIBS)
llex.c:
sed '/void luaX_next/i#include "proxy.c"' $(LUASRC)/$# > $#
llex.o: proxy.c
clean:
-rm -f $(OBJS) core core.* a.out $(MYNAME)
# eof
Hand-build solution:
cp /usr/local/src/lua-5.1.3/src/llex.c .
Hand-edit llex.c to add the line #include "proxy.c" before the line starting with void luaX_next (line 446 for me).
Now run make, which will succeed.

Answer 1

You can find the answer in the sed manual, and it is in the Makefile lines
llex.c:
sed '/void luaX_next/i#include "proxy.c"' $(LUASRC)/$# > $#
Some variable expansion takes place here:
$(LUASRC) is expanded to the variable set above -> $(LUA)/src. Recurse as needed.
$# is replaced with the current target (llex.c)
So this recipe says:
In order to obtain the target llex.c (which will be processed later through other recipes), apply a stream editing command to the file $LUASRC/llex.c and write it to llex.c.
The stream editing command is: look for text "void luaX_next", before printing it, insert line "#include "proxy.c"".
Problem is, the command to do this is not "i" but "i\(newline)", which conflicts with a requirement of Makefiles that recipes must be on a single line.
I suspect that in order to fix your Makefile you need to use a different command than sed; awk can fit the bill although it's a bit more complex.

Answer 2

This line works in Mac OS X and in Linux:
sed '/void luaX_next/{h;s/.*/#include "proxy.c"/;p;g;}' $(LUASRC)/$# > $#