Undefined reference, presume makefile is not using headerfiles

Question

#include <iostream>
#include <string>
#include <fstream>

int main (void)
{
    // Nothing here. 
}

I am using Makefile to compile.

CXXFLAGS    = -std=c++11 -O2 -g -Wall -fmessage-length=0

OBJS        = ProgramEntry.o

LIBS        =

TARGET      = Reading

$(TARGET):  $(OBJS)
    $(CXX) -o $(TARGET) $(OBJS) $(LIBS)

all:    $(TARGET)

clean:
    rm -f $(OBJS) $(TARGET)

Resulting in undefined reference.

undefined reference to --

I think makefile is not using any header file. May I know how to fix the make file, in case if I add a directory for header files.

Answer 1

It is using the headers, or you'd get a compiler error, not a linkage error.

Change the following line to this:

OBJS        = ProgramEntry.o GetNodes.o GetElements.o MeshData.o

Or

OBJS        = *.o

To add all objects in the current directory.

Answer 2

You're only linking in one of your object files, so the functions defined in the others don't make it into your program.

Add all your .os to OBJS. That appears to be the point of that variable, after all?