Error when running: make clean - makefile

Question

I am trying to build some simulation software using makefile provided by them after I have made some changes to the libraries. But when I run make clean, it stops midway and I get the following error
rm: invalid option -- 'l'
Try `rm --help' for more information.
make: *** [neat] Error 1
I checked the man page for rm and there is no -l option, but I don't know why this command is being executed with -l option. Is there anyway to ignore this, or find out which specific file is causing the problem?
EDIT:
I have figured out the source of the error, but dont know how to edit it to make it work properly. Below is a snippet from an included Makefile with the faulty line:
UDP_INTERFACE_SRCS = \
$(UDP_INTERFACE_DIR)/interfaceudp_app.cpp \
$(UDP_INTERFACE_DIR)/interfaceudp.cpp \
$(UDP_INTERFACE_DIR)/external_interface_udp.cpp \
$(UDP_INTERFACE_DIR)/packet_send.cpp \
$(UDP_INTERFACE_DIR)/addr.cpp \
$(UDP_INTERFACE_DIR)/packet_capture.cpp -lpcap \
$(UDP_INTERFACE_DIR)/queue.cpp
In particular, the line: $(UDP_INTERFACE_DIR)/packet_capture.cpp -lpcap \
is causing the error. What does the "-lpcap" added after "packet_capture.cpp" do? Now if I try to remove it, "make" gives an error saying:
./interfaces/extinterface/src/packet_capture.o: In function pcap_sniff_packets(void*)': /home/qualnet/4.5/main/../interfaces/extinterface/src/packet_capture.cpp:63: undefined reference to pcap_setdirection' make: *** [../bin/qualnet] Error 1
I checked the line number 63 in packet_capture.cpp in an effort to understand what -lpcap means. But I have no idea what that code does.

Answer 1

(This is clearly an iterative process, and the comments are getting long, so I'd better start an answer.)
You say: "When I put echo SIM_JOBS: $(SIM_OBJS) in the rule, i get the following when i run make clean: rm -f ../bin/qualnet ../bin/radio_range"
This doesn't make sense. You should get something like
SIM_JOBS: ../bin/qualnet ../bin/radio_range
rm -f ../bin/qualnet ../bin/radio_range
or
SIM_JOBS: something/else
rm -f ../bin/qualnet ../bin/radio_range
or at least
SIM_JOBS:
rm -f ../bin/qualnet ../bin/radio_range
This suggests that you are looking at the wrong rule: the rule which produces rm -f ../bin/qualnet ../bin/radio_range is not the rule in which you put the echo ... command. If it is the rule and you were just being imprecise in the report, put this right above the clean rule:
SIM_JOBS=../bin/qualnet ../bin/radio_range
and tell us what happens.
EDIT:
Sorry, I wrote `SIM_JOBS` when I meant `SIM_OBJS`.
The `echo` command was outside the rule, where it cannot work.
It looks as if the problem. Could you edit your question to show the line you mentioned to #thiton, and a few previous lines? It looks as if the flag "-lpcap" is getting into a variable, where it doesn't belong.
EDIT:
The "-lpcap" is a kludge. My guess is that it's an option intended for the linker. Suppose you want to link a bunch of object files into an executable, and you want to search a certain library called "pcap":
gcc foo.o -lpcap bar.o baz.o
The order is very important; when the linker is searching for something, you want it to search foo.o first, then pcap, then bar, then baz. It's a question of precedence. But you want to store those filenames in a nice tidy variable, and how will you insert the lpcap at the right place? You could do it a good way, or use a lazy hack like this:
OBJECTS = foo.o -lpcap bar.o baz.o
gcc $(OBJECTS)
And if you're deducing the OBJECTS from the SOURCES, you have to put the hack in earlier:
SOURCES = foo.cc -lpcap bar.cc baz.cc
OBJECTS = $(SOURCES:.cc=.o)
Whoever wrote these makefiles saved half an hour with this kludge, and it's taking you days to fix it. If you can confirm that this is what's happening, the easiest way is probably to split the list in two:
SOURCES_LEFT = foo.cc
SOURCES_RIGHT = bar.cc baz.cc
OBJECTS_LEFT = $(SOURCES_LEFT:.cc=.o)
OBJECTS_RIGHT = $(SOURCES_RIGHT:.cc=.o)
gcc $(OBJECTS_LEFT) -lcap $(OBJECTS_RIGHT)

Answer 2

Like #AndrejPanjkov noted in the comments, the standard tool to find out what exactly is going on in Makefiles is the -n (--dry-run) switch of make. It prints all commands as they would be run by the shell, even those normally silenced (e.g. via #).
Have a long, hard look in this output for any pattern like ' -l' (piping the output to less and using / helps). If that doesn't help, try running all commands output by -n by hand in make's shell (normally /bin/sh) or try removing all the silencers (# characters at a rule's start) from the Makefile and running make clean, checking the last line of output.