Why debug execution order doesn't match code order in c++?

Question

I am new to C++. When I debugged in Clion, I found that the execution order using Step over (F8) doesn't match the real code's order. So far, I think the most possible reason is compiler optimization. I have no impression that I've enabled this and I am using LLDB to debug.

It seems related to this answer: Why don't my breakpoints run in order? GCC and C

Here is my code:

int depthSum(vector<NestedInteger> &nestedList) {
        deque<pair<int, NestedInteger>> q;
        int level = 1;
        for (NestedInteger n : nestedList) {
            q.push_back({ level, n});
        }

        int res = 0;
        while (!q.empty()) {
            auto pair = q.front();
            q.pop_front();
            if (pair.second.isInteger()) {
                level--;
                res = (level * (pair.second.getInteger()));
                cout << res << endl;
            } else {
                level++;
                for (NestedInteger nestedInteger : pair.second.getList()) {
                    q.push_front({level, nestedInteger});
                }
            }
        }
        return res;
    }

When the breakpoint step at the res = (level * (pair.second.getInteger())); and then press the F8 it jumps back to the level--, and then press F8 jump to the res = (level * (pair.second.getInteger()));, once again press F8 that will jump to the cout << res << endl;

marked order:

Is this really because code reordering? By the way, the result of the code logical without error though debugging order not match expectation, but I have not found some open code optimization option in my project.

---

add profile of CMake

I tried to avoid optimization but problem still exists.

---------------------------- updated

This is working, but I have no clue why -O0 is not working. Logically speaking -O0 should be working because this avoids all optimization.

-DCMAKE_C_FLAGS_DEBUG:STRING="-g -O1" -DCMAKE_CXX_FLAGS_DEBUG:STRING="-g -O1"

Answer 1

you're IDE probably is in release mode configuration ... so change it to debug mode