C/C++: ==ERROR: LeakSanitizer: detected memory leaks — Direct leak of N byte(s)

Meaning

The report groups leaks by allocation stack ("Direct leak" = nothing points to it; "Indirect leak" = reachable only from a leaked block). Fix the largest and most frequent first. Not every leak is a bug in short-lived tools, but in servers and loops they accumulate until bad_alloc or the OOM killer.

Common causes

• new/malloc without matching delete/free
• Early return or exception between allocation and free
• Cyclic shared_ptr references (use weak_ptr for back-links)
• Container of raw owning pointers never deleted
• Third-party handle not closed (fopen, dlopen, library init)

Detailed fix by platform

Code examples

#include <memory>
#include <vector>

struct Node { std::vector<std::unique_ptr<Node>> kids; };

int main() {
    auto root = std::make_unique<Node>();                // freed automatically at scope exit
    root->kids.push_back(std::make_unique<Node>());
    // Node* leak = new Node;                            // "Direct leak of 24 byte(s)"
}

How to diagnose

1. Stack — Which allocation stack leaks the most?
2. Ownership — Who should free it?
3. Exit — Early returns or exceptions?

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