Calling function from other C++ source doesn't work - c++

Question

I've looked at several posts of the same questions on here and as far as I've figured I've done what they said to do. However, I still get a "undefined reference to `cmb::functionA()'" warning.
I have the header:
//combine.h
#ifndef COMBINE_H
#define COMBINE_H
namespace cmb
{
void functionA();
}
#endif
Function source file:
// combine.cc
#include <iostream>
#include "combine.h"
using namespace std;
namespace cmb
{
void functionA()
{
cout << "print something\n";
}
}
And main:
//main.cc
#include "combine.h"
using namespace std;
using namespace cmd;
int main(int argc, char *argv[])
{
functionA();
}
It is now working when compiling manually (g++ -o Test *.cc -Wall --std=c++17) but using make still gives me the same error. I really don't understand make files so any help would be appreciated.
makefile:
CXX := g++
CXXFLAGS += -Wall -std=c++17
LIBSRCS = $(filter-out main.cc,$(shell find -name \*.cc))
LIBOBJS = $(patsubst %.cc,%.o,$(LIBSRCS))
main: main.o combine.o libproject.a
$(CXX) $(CPPFLAGS) $(CXXFLAGS) $(LDFLAGS) -o $# $<
$(LIBOBJS): %.o: %.cc
$(CXX) $(CPPFLAGS) $(CXXFLAGS) -c -o $# $<
libproject.a: $(LIBOBJS)
ar rcs $# $^
clean:
rm -f libproject.a $(LIBOBJS)
.PHONY: clean
I just use make main in terminal.

Answer 1

You must add combine.o after main: in the makefile.

Answer 2

Since you use a library, you need to tell the linker to use it (LDFLAGS), and it should be after the main in g++ command. As in previous comments, the using namespace cmd needed to be changed to cmb
This one worked for me:
CXX := g++
CXXFLAGS += -Wall -std=c++17
LIBSRCS = $(filter-out ./main.cc,$(shell find -name \*.cc))
LIBOBJS = $(patsubst %.cc,%.o,$(LIBSRCS))
LDFLAGS += -L. -lproject
main: main.o libproject.a
$(CXX) $(CPPFLAGS) $(CXXFLAGS) -o $# $< $(LDFLAGS)
libproject.a: $(LIBOBJS)
ar rcs $# $^
.PHONY: clean
clean:
rm -f libproject.a $(LIBOBJS) main main.o
I also needed to add ./ in filtering out main.cc
Example run:
jontte#jontte-Latitude-E5420:~/Temp/maketest$ make
g++ -Wall -std=c++17 -c -o main.o main.cc
g++ -Wall -std=c++17 -c -o combine.o combine.cc
ar rcs libproject.a combine.o
g++ -Wall -std=c++17 -o main main.o -L. -lproject
jontte#jontte-Latitude-E5420:~/Temp/maketest$ ./main
print something
jontte#jontte-Latitude-E5420:~/Temp/maketest$ make clean
rm -f libproject.a ./combine.o main main.o
jontte#jontte-Latitude-E5420:~/Temp/maketest$