Errors undefined reference Class:: function-CodePudding

i am quite new to c so i have an assignement and trying to experiment a bit before tackling the process of building an AST tree. Trying to input a string expressing (operator and operands ) and splitting it as in the python split but it seems i keep getting either basic class structure problems or compilation problems not sure .

expr.h file

#include <string>

class BuildAst
{
public:
    void build(std::string expr);
protected:
    char opera;
    char left_child;
    char right_child;

};

expr.cpp file

#include "expr.h"
#include <string>
#include <string.h>
#include <iostream>
#include <sstream>


void BuildAst::build(std::string expr)
{
   std::string str1, str2;
   std::stringstream s(expr);
   s>>str1>>str1;
   std::cout<<str1<<std::endl;
   std::cout<<str2<<std::endl;
};

main.cpp file

#include "expr.h"
#include <vector>
#include <string>
#include <iostream>


int main() {
 std::string s;
 std::cout << "Enter the expression\n";
 std::cin >> s;
 BuildAst ast;
 ast.build(s);

 };

makefile

CFLAGS="--std=c  14"
all: main tests

expr:
   $(CC) $(CFLAGS) -c -o expr.o expr.cpp

main: expr
   $(CC) $(CFLAGS) -o expr main.cpp expr.o

tests: expr
   $(CC) $(CFLAGS) -o tests testcases.cpp expr.o

clean:
   rm *.o expr tests

The input expression i'm trying to use is 3 5 and output should be 3,5 And i keep getting the following errors

Tried adding to the 3 files (main.cpp/ expr.cpp/expr.h)

#define _GLIBCXX_USE_CXX11_ABI 0/1

then the error i am getting changed to

Could you help me please and thank you.

CodePudding user response：

I had a similar question to this a while back. The answer that robthebloke had answered perfectly for me. Not sure if this is as applicable for you, but my post is linked HERE.

CodePudding user response：

okay, turned out i'm not running the files as a project in codeblocks. Problem fixed