Trying to compile the Paho MQTT C example on Raspberry Pi - c

Question

I am trying to run the Paho MQTT example in C on my raspberry pi: https://www.eclipse.org/paho/clients/c/
I tried just downloading the pre-built binaries and linking to lpaho-mqtt3c
I put that library here: /home/pi/mqtt_C_testing/Eclipse-Paho-MQTT-C-1.3.1-Linux/lib
And I added: LD_LIBRARY_PATH=/home/pi/mqtt_C_testing/Eclipse-Paho-MQTT-C-1.3.1-Linux/lib/
My makefile looks like this:
IDIR = /home/pi/mqtt_C_testing/Eclipse-Paho-MQTT-C-1.3.1-Linux/include
LDIR = /home/pi/mqtt_C_testing/Eclipse-Paho-MQTT-C-1.3.1-Linux/lib
CC = gcc
LD = gcc
CFLAGS = -Wall
LIBS = -lpaho-mqtt3c
PROG_NAME = main
# directories in project
BIN = bin
SRC = src
OBJ = obj
INCLUDE = include
INCLUDES = -I./$(INCLUDE)
all : $(PROG_NAME)
$(PROG_NAME) : $(BIN)/$$#
$(BIN)/% : $(OBJ)/%.o
$(CC) $(CFLAGS) $^ -o $# $(LIBS)
$(BIN)/main : $(addprefix $(OBJ)/, \
main.o)
$(OBJ)/main.o : $(addprefix $(INCLUDE)/, \
MQTTProperties.h MQTTReasonCodes.h MQTTSubscribeOpts.h MQTTClient.h \
MQTTClientPersistence.h MQTTAsync.h)
$(OBJ)/%.o : $(SRC)/%.c
$(CC) $(INCLUDES) $(CFLAGS) -c $< -o $#
.PHONY: clean
clean:
rm -f $(OBJ)/*.o
When I try to build though, gcc cannot find the library:
gcc -Wall obj/main.o -o bin/main -lpaho-mqtt3c
/usr/bin/ld: cannot find -lpaho-mqtt3c
collect2: error: ld returned 1 exit status
make: *** [makefile:26: bin/main] Error 1
My directory structure is like this:
pi#raspberrypi:~/mqtt_C_testing $ ls
bin Eclipse-Paho-MQTT-C-1.3.1-Linux include makefile obj src
And I have main.c (the mqtt example file) in src and I put all the MQTT header files in include.
The library files for mqtt are here: /home/pi/mqtt_C_testing/Eclipse-Paho-MQTT-C-1.3.1-Linux/lib
I'm really not sure if I'm the right track at all here, so any help is appreciated. Thanks!

Answer 1

To get this to compile I did the following:
1) I built the lib by cloning the repo at github.com/eclipse/paho.mqtt.c and ran make then make install. This puts the .so files in /usr/local/lib
2) I put all the .h files in the main folder of my project directory: /home/pi/mqtt_C_testing/
3) I called the paho mqtt synchronous example main.c and have that also in the main directory.
4) I can then simply use: gcc -Wall -o test main.c -lpaho-mqtt3c to build and create an executable called "test"
5) I had success writing a makefile also that is run just with make. I'm a noob to all this, but I found this website (http://www.cs.colby.edu/maxwell/courses/tutorials/maketutor/) really helped with creating the makefile. I have not really had success putting the .h files in their own include directory yet though.
CC = gcc
CFLAGS=-I.
DEPS = MQTTAsync.h MQTTClientPersistence.h MQTTProperties.h MQTTClient.h MQTTReasonCodes.h MQTTSub$
OBJ = main.o
LIBS= -lpaho-mqtt3c
%.o: %.c $(DEPS)
$(CC) -c -o $# $< $(CFLAGS)
mainmake: main.o
$(CC) -o $# $^ $(CFLAGS) $(LIBS)