C vs C++

versus.md

C vs C++

Write Hello World

C++ version

#include <iostream>
int main(){
    std::cout << "Hello World" << std::endl;
}

C version

#include <stdio.h>
int main(){
    puts("Hello World");
    return 0;
}

Compile

for C++

g++ main.cpp -o main

for C

gcc main.c -o main

ldd output

for C++

	linux-vdso.so.1 (0x00007ffc026df000)
	libstdc++.so.6 => /usr/lib/gcc/x86_64-pc-linux-gnu/13/libstdc++.so.6 (0x00007f5fdc600000)
	libm.so.6 => /lib64/libm.so.6 (0x00007f5fdc863000)
	libgcc_s.so.1 => /usr/lib/gcc/x86_64-pc-linux-gnu/13/libgcc_s.so.1 (0x00007f5fdc5db000)
	libc.so.6 => /lib64/libc.so.6 (0x00007f5fdc402000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f5fdc965000)

for C

	linux-vdso.so.1 (0x00007ffd509f5000)
	libc.so.6 => /lib64/libc.so.6 (0x00007f6fce003000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f6fce1ff000)

Binary file

readelf -a main | wc -l

for C++: 270 for C: 248

du -b main

for C++: 16032 for C: 15480

nm --dynamic main | wc -l

for C++: 10 for C: 6

Object

Objects in C++

OOP suppoted.

class test {
private:
    double value;

public:
    test(double l) {
        value = l;
    }
}
void main(){
    test t(12);
    t.value = 23;
}

Objects in C

OOP is not supported but we can use struct.

typedef struct _test {
    double value;
} test;

test* test_new(double l){
    test *ctx;
    ctx->value = l;
    return ctx;
}

void main(){
    test *t = test_new(12);
    t->value = 23;
}

Using with other languages

Use C in C++

extern "C" {
    // Write C code here
}

Use C++ in C

1. Create header in C

#ifdef __cplusplus
extern "C" {
#endif

typedef void* test;

test test_new(double l);
void test_set_value(test* ctx, double l);
double test_get_value(test* ctx);
#ifdef __cplusplus
}
#endif

2. create wrapper in C++

#include <test>
extern "C" {
    test test_new(double l){
        Test* t = new Test(l);
        return (test) t;
    }

    void test_set_value(test* ctx, double l){
        Test* t = (Test*)ctx;
        t->value = l;
    }
    double test_get_value(test* ctx){
        Test* t = (Test*)ctx;
	return t->value;
    }
}

3. compile like this

g++ test.cpp -c -o test.o
gcc main.c -c main.o
gcc main.o test.o -o main -lstdc++

Exception handling

in C++

Supported

try {
    // buggy code here
} catch(const std::exception& e) {
    // write message here
}

in C

Not supported but we can use setjmp

#include <stdio.h>
#include <signal.h>
#include <setjmp.h>

jmp_buf env;
#define try \
        int ret = setjmp(env); \
        if (ret == 0) {

#define catch(exception) \
        } else if (ret == exception) {

#define throw(exception) \
            longjmp(env, exception)

#define endtry }

#define FloatingPointException 1
void handle_floating_exception(){
     throw(FloatingPointException);
}

int main() {
    // Install signal handler for division by zero
    signal(SIGFPE, handle_floating_exception);

    try {
        int a = 10;
        int b = 0;
        printf("Attempting division by zero\n");
        int result = a / b; // Division by zero
        printf("This won't be executed\n");
    }
    catch(FloatingPointException) {
        printf("Handled floating point exception\n");
    } endtry

    return 0;
}