GCC linking a static library - c++

Question

I have seen questions like these on SO but everyone has different answers and directory structures that aren't working for me.
My makefile:
CC = g++
DEBUG = -g -std=c++11
TARGET = main
OBJECT_FILES = BingResultSet.o main.o
INC_PATH = -I HTTPClientLib/include
LIB_PATH = -L HTTPClientLib/lib/
start: clean BingResultSet.o main.o
$(CC) $(DEBUG) $(INC_PATH) $(LIB_PATH) $(OBJECT_FILES) -o $(TARGET)
rm -f *.o
BingResultSet.o: BingResultSet.cpp BingResultSet.h
$(CC) $(DEBUG) $(INC_PATH) $(LIB_PATH) -c BingResultSet.cpp
main.o: main.cpp
$(CC) $(DEBUG) $(INC_PATH) $(LIB_PATH) -c main.cpp
clean:
rm -f $(OBJECT_FILES) $(TARGET)
My file structure:
/Desktop/DataMiner/.cpp, .h, and makefile
/Desktop/DataMiner/HTTPClientLib/include/HTTPClient.h
/Desktop/DataMiner/HTTPClientLib/lib/HTTPClient.a
What's the correct way to link my static lib in my makefile?

Answer 1

Here's my $0.02:
there was no static library involved. Assuming you meant the .o files
you mix dependencies and build rules, instead, avoid repeating build rules:
$(TARGET): $(OBJECT_FILES)
$(CXX) $(DEBUG) $(INC_PATH) $^ -o $# $(LIB_PATH)
%.o: %.cpp
$(CXX) $(DEBUG) $(INC_PATH) -c $< -o $#
You used CC for a C++ compiler. That's strange. Use CXX
You used LDFLAGS when you were just compiling
You hardcoded the source and destination paths. Instead use the automatic variables ($^, $< for source; $# for destination)
You tried to hardcode header dependencies. That's error-prone and messes up source specification (you don't want $^ to list .h files in your command line...). Instead, use gcc -MM¹ to generate the dependencies for you!
Next, do a conditional include of those dependencies:
.depends:
$(CXX) -MM $(CXXFLAGS) -c *.cpp > $#
-include .depends
It's usually handy to keep the .o files so you can speed up builds. Of course, this was not a good plan until you generated the header dependencies automatically. If you insist, you can comment the .PRECIOUS target. Intermediate targets are automatically deleted by GNU Make
Here's the integrated offering I ended up with:
CXX = g++
TARGET = main
OBJECT_FILES = BingResultSet.o main.o
INC_PATH = -I HTTPClientLib/include
LIB_PATH = -L HTTPClientLib/lib/
CPPFLAGS = -g -std=c++11
CPPFLAGS+= $(INC_PATH)
# standard derived flags:
CXXFLAGS+=$(CPPFLAGS)
LDFLAGS+=$(LIB_PATH)
start: .depends $(TARGET)
$(TARGET): $(OBJECT_FILES)
$(CXX) $(CXXFLAGS) $^ -o $# $(LDFLAGS)
%.o: %.cpp
$(CXX) $(CXXFLAGS) -c $< -o $#
clean:
rm -f .depends $(OBJECT_FILES) $(TARGET)
# to keep the .o files:
.PRECIOUS: $(OBJECT_FILES)
.depends:
$(CXX) -MM $(CXXFLAGS) -c *.cpp > $#
-include .depends
On a very simple sample set of files you get:
$ make clean
rm -f .depends BingResultSet.o main.o main
$ make
g++ -MM -g -std=c++11 -I HTTPClientLib/include -c *.cpp > .depends
g++ -I HTTPClientLib/include -c BingResultSet.cpp -o BingResultSet.o
g++ -I HTTPClientLib/include -c main.cpp -o main.o
g++ -I HTTPClientLib/include BingResultSet.o main.o -o main -L HTTPClientLib/lib/
$ cat .depends
BingResultSet.o: BingResultSet.cpp BingResultSet.h
main.o: main.cpp BingResultSet.h
test.o: test.cpp
¹ (or similar, see man-page)