Miri & Valgrind

rustup toolchain install nightly
rustup +nightly component add miri
cargo +nightly miri test


valgrind ./my_program  # программу уже скомпилировали

use std::alloc::{alloc, dealloc, Layout};

// BUG 1: Use-after-free (we'll read memory after freeing it)
fn use_after_free() -> u8 {
    let layout = Layout::new::<u8>();
    let ptr = unsafe { alloc(layout) };

    // Write something
    unsafe {
        *ptr = 42;
    }

    // Free the memory
    unsafe {
        dealloc(ptr, layout);
    }

    // BUG: Reading after free! This is undefined behavior.
    let value = unsafe { *ptr };
    value
}

// BUG 2: Memory leak (allocate but never free)
fn memory_leak() -> *mut u8 {
    let layout = Layout::new::<u8>();
    let ptr = unsafe { alloc(layout) };
    unsafe {
        *ptr = 99;
    }

    // BUG: We never call dealloc! The memory leaks.
    ptr
}

// BUG 3: Miri-specific - violating Rust's aliasing rules
fn aliasing_violation() {
    let mut x = 5;
    let raw_ptr = &mut x as *mut i32;

    // Create a second mutable pointer to the same memory
    let raw_ptr2 = &mut x as *mut i32;

    unsafe {
        // Miri catches this: two mutable references to same data in scope
        *raw_ptr = 10;
        *raw_ptr2 = 20; // Undefined behavior per Rust's Stacked Borrows rules
    }
}

fn main() {
    println!("Testing use-after-free...");
    let val = use_after_free();
    println!("Read value: {} (this might be garbage)", val);

    println!("\nLeaking memory...");
    let _leaked = memory_leak();
    println!("Memory leaked successfully!");

    println!("\nViolating aliasing rules...");
    aliasing_violation();
    println!("Aliasing violation completed (somehow)");
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_use_after_free() {
        let val = use_after_free();
        // We're just calling it - the bug is inside
        assert!(val == 42 || val != 42); // Always passes, but the UB is the problem
    }

    #[test]
    fn test_aliasing_violation() {
        aliasing_violation(); // Miri should catch this
    }
}