Undefined reference to function in g++ while using static linking on Linux - c++

Question

I am learning programming under Linux, and I faced the following problem during linking.
My directory structure
libraries
|-- archive_sample
| |-- calc.h
| |-- calc.cpp
| |-- makefile
|
|-- test_archive
|-- main.cpp
|-- makefile
calc.h
#ifndef __CALC__H__
#define __CALC__H__
int add(int a, int b);
int sub(int a, int b);
#endif
calc.cpp
#include "calc.h"
int add(int a, int b)
{
return (a + b);
}
int sub(int a, int b)
{
return (a - b);
}
File archive_sample/makefile:
libcalc.a : calc.o
ar rcs libcalc.a calc.o
calc.o : calc.cpp calc.h
g++ $(CFLAGS) -c calc.cpp
clean :
rm -f libcalc.a calc.o
When I run "make" from archive_sample directory, it executes successfully and calc.o and libcalc.a are created in the same directory.
main.cpp
int main()
{
int a, b;
std::cin >> a >> b;
std::cout << "a + b : " << add(a, b) << std::endl;
std::cout << "a - b : " << sub(a, b) << std::endl;
return (0);
}
Compiling with
g++ -c -I../archive_sample main.cpp
succeeds and main.o is created. However linking with
g++ -L../archive_sample -lcalc main.o -o test
gives the following error:
main.o: In function main:
main.cpp:(.text+0x3e): undefined reference to add(int, int)
main.cpp:(.text+0x84): undefined reference to sub(int, int)
collect2: error: ld returned 1 exit status
Where am I going wrong?
Also "make" is also not working for the following makefile.
test_archive/makefile
test : main.o
g++ -L../archive_sample -lcalc main.o
main.o : main.cpp calc.h
g++ $(CFLAGS) -c -I../archive_sample main.cpp
clean :
rm -f test *.o
with error
make: *** No rule to make target `calc.h', needed by `main.o'. Stop.
How can I fix this problem?

Answer 1

For the first error, since main.cpp and archive_sample are in the same directory, you shouldn't specify -Larchive_sample rather than -L../archive_sample.
For the second error, your calc.h is in the archive_sample directory, so the dependency should be listed as archive_sample/calc.h.