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rust.global_mutable_state

Correctness High

Detects mutable global state that causes race conditions and testing difficulties.

Why It Matters

Global mutable state:

Race conditions — Concurrent access bugs
Hard to test — State leaks between tests
Implicit coupling — Hidden dependencies

Example

// ❌ Before (static mutable)
static mut COUNTER: i32 = 0;

fn increment() {
    unsafe {
        COUNTER += 1; // Data race!
    }
}

// ✅ After (atomic or explicit state)
use std::sync::atomic::{AtomicI32, Ordering};

static COUNTER: AtomicI32 = AtomicI32::new(0);

fn increment() {
    COUNTER.fetch_add(1, Ordering::SeqCst);
}

// Or pass state explicitly:
fn increment(counter: &AtomicI32) {
    counter.fetch_add(1, Ordering::SeqCst);
}

What Unfault Detects

static mut declarations
Global lazy_static without synchronization
Shared state without proper guards

Auto-Fix

Unfault can suggest atomic types or explicit state passing.