Makefile

CC  = g++
CXX = g++

CXXFLAGS = -g -Wall -std=c++20

• CC: compiler for C source files
• CXX: compiler for C++
• -std=c++20

hello.cpp

#include <iostream>           // cpp headers don't have .h
int main() {
    std::cout << "hello world c" << 2 << "cpp" << std::endl;
}

• cout: console output C++ has namespace. In C, if two library have the same function names, linker can’t link
  int and char * are mixed
• Left shift << redefined for char * (can’t redefine for int)

Target

target: source

• Tab: recipe

CC = g++
CXX = g++

If CC = gcc, gcc will invoke linker ld with the C standard libraries, problematic!!!

• Or specify ld hello.o libstdc++... in the recipe line

hello: hello.o
	g++ hello.o -o hello

hello: hello.cpp
	g++ -g -Wall -std=c++20 -c hello.c -o hello.o

.PHONY: clean
clean: 
	rm *.o hello
	
.PHONY: all
all: clean hello

Namespace

#include <iostream>           // cpp headers don't have .h
int main() {
	using namespace std;
    cout << "hello world c" << 2 << "cpp" << endl;
}

Define your own namespace:

#include <iostream>
namespace c2cpp {
    int main() {
        using namespace std;
        cout << "hello c" << 2 << "cpp!" << endl;
        return 0;
    }
} // namespace c2cpp

int main() {     // global namespace
    return c2cpp::main();
}

String

In standard library: string

string s; 
s = "hello"; 
s = s + "world"

• Can’t concatenate by s + t
• s = s + 100 won’t work. operator+() undefined
• s += 100 works. operator+=() overloaded