Makefile: “No rule to make target…” with multiple working directories

Question

I'm trying to run this makefile, and run into an issue. Make tells me

"No rule to make target 'UDP_Server.o', needed by 'SendRawData',

Since I've given it the working directories of the files however, shouldn't the rule for %.o file work just fine? I'm launching make within the /thing/asset/src directory, and I don't care where it puts the o files or the program, as long as I can access them. Here's my makefile:

CC = g++

INC += -I/home/pi/thing/ 
INC += -I/home/pi/thing/Asset/src/
INC += -I/home/pi/thing/Server/src/
INC += -I/home/pi/thing/Shared/NetworkInterface/src/
INC += -I/home/pi/mercuryapi/c/src/

LIB = /home/pi/mercury/c/src/api/

CFLAGS  = -std=c++11 -Wno-write-strings
LDFLAGS = -L$(LIB) -static -l libmercuryapi 

SOURCES += UDP_Client.cpp
SOURCES += UDP_Server.cpp
SOURCES += rawData.cpp
SOURCES += packetMethods.cpp
SOURCES += parseData.cpp
SOURCES += SendRawData.cpp

OBJECTS =  $(SOURCES:.cpp=.o)

DEPS  = UDP_Client.h
DEPS += UDP_Server.h
DEPS += packet.h
DEPS += rawData.h
DEPS += packetMethods.h
DEPS += parseData.h
DEPS += tm_reader.h

default: SendRawData

%.o: %.cpp $(SOURCES) $(DEPS)
    $(CC) $(CFLAGS) $(INC) -c $< -o $@ 

SendRawData: $(OBJECTS)
    $(CC) $(CFLAGS) $(LDFLAGS) $(INC) $< -o SendRawData

client: cmain.cpp UDP_Client.cpp
    $(CC) $(CFLAGS) cmain.cpp UDP_Client.cpp -o client

.cpp.o:
    $(CC) $(CFLAGS) $(INC) -c $< -o $@

.PHONY: clean
clean:
    rm *.o

If it helps at all, here is the directory structure visualized:

/home/pi/thing/
├── Asset
│   ├── README.txt
│   └── src
│       ├── makefile
│       ├── README.txt
│       ├── SendRawData.cpp
│       ├── UDP_Client.cpp
│       └── UDP_Client.h
├── Server
│   └── src
│       ├── README.txt
│       ├── server
│       ├── UDP_Server.cpp
│       ├── UDP_Server.h
│       └── UDP_Server.o
└── Shared
    ├── NetworkInterface
    │   ├── README.txt
    │   └── src
    │       ├── header.h
    │       ├── packet.h
    │       ├── packetMethods.cpp
    │       ├── packetMethods.h
    │       ├── parseData.cpp
    │       ├── parseData.h
    │       ├── rawData.cpp
    │       ├── rawData.h
    │       └── testing.cpp
    └── README.txt

Answer 1

Make cares where you put the files. You need to tell make where the source files are located.

The ugly, tedious, but explanatory solution is to add the path when specifying the dependency. Instead of

SOURCES += UDP_Client.cpp

write

SOURCES += ../../Server/src/UDP_Client.cpp

The beautiful and simple solution is to use makes VPATH variable:

https://www.gnu.org/software/make/manual/html_node/General-Search.html

For example

VPATH = "../../Server/src/UDP_Client.cpp:<list of : separated paths>"

This solution might only work if your using gnu make.