Question

#include <iostream>
#include <vector>

using namespace std; 
int in;

bool isPrime(int n) {
    for (int i = 3; i <= n; i ++) {
        if (n%i != 0) {
            return false;
        }
    }
    return true;
}

vector<int>* generateVector(int n) {
    vector<int> v;
    for (int i = 2; i < 20; i ++) {
        if (i == n) {
            continue;
        }

        if (isPrime(i+n)) {
            v.push_back(i);
        }
    }
}

int main()
{
    while(1) {
        cin >> in;
        vector<int>* nVectors[21];
        for (int i = 1; i <= 20; i ++) {
            nVectors[i] = generateVector(i);
        } <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
    }
}

This some c++ code. And i would like to make a break point just after the for loop(the arrow show the position).
I have found one way to solve it through adding a statement after it then make break point in this statement. But adding a statement without a meaning make not feeling good. So is there a better solution?

I am using GDB for debugging.

PS: I have already known how to set breakpoint in gdb. My intent is to break after the for loop ends, and display what in nVectors. Thanks.

Sorry for all. It’s not the issue about the gdb or debugging skill, but there is a bug in my code. So when i print nVectors, nothing was printed. After fixing it, every method you provides works fine. Thanks.

Answer 1

You can use a assembly break point, just need to understand the assembly code of for loop.

gdb <your_bin>
layout split
break *0x80488ad              #assmebly code will look like 
                              #0x80488ad     jmp    0x8048874 <main+18>