SafeManuallyDrop

A safe version of ManuallyDrop with various features and options to track undefined behavior when working with ManuallyDrop.

Use

1. easy

use SafeManuallyDrop::ManuallyDrop;
use std::ops::Deref;

fn main() {
	/*
		ManuallyDrop - Depending on the build flag, a protected version of ManuallyDrop 
		or an unprotected version of ManuallyDrop with a default trigger. 
	*/
	if ManuallyDrop::is_safe_mode() {
		// ManuallyDrop is protected, let's do the standard behavior ManuallyDrop
		// but at the end we'll make the undefined behavior ManuallyDrop.
		
		// 
		let mut data = ManuallyDrop::new(vec![1, 2, 3, 4]);
		println!("data: {:?}", data.deref());
		
		#[allow(unused_unsafe)] // to avoid warning if the always_compatible_stdapi flag is not used (can be removed)
		unsafe {
			assert_eq!(data.is_next_trig(), false); // VALID
			ManuallyDrop::drop(&mut data); // VALID
			assert_eq!(data.is_next_trig(), true); // VALID
			
			// <<-- PANIC
			/*
				thread 'main' panicked at 'Undefined behavior when using 
				ManuallyDrop(combo_replace_manudropstate), instead of the expected default 
				state, the current state: DropModeTrig.', src/core/trig/hook.rs:14:5
			*/
			ManuallyDrop::drop(&mut data); // INVALID, COMBO DROP
		}
	}else {
		println!("#[0] ManuallyDrop is an alias for AutoSafeManuallyDrop, ");
		println!("#[1] ManuallyDrop in the release build has no protection by default,");
		println!("#[2] if ManuallyDrop is not protected it will be the same as in std.");
		println!("#[3] To run the protected version, use `cargo run --example easy` or ");
		println!("`CARGO_PROFILE_RELEASE_DEBUG_ASSERTIONS=\"true\" cargo run --example easy --release`");
		println!();
		println!("Or use concrete types instead of auto (AutoSafeManuallyDrop, AutoSafePanicManuallyDrop, AutoSafeHookManuallyDrop, AutoSafeCounterManuallyDrop, AlwaysSafeManuallyDrop, AlwaysSafePanicManuallyDrop, AlwaysSafeHookManuallyDrop, AlwaysSafeCounterManuallyDrop) specific data types with specific behavior.");
	}
}

2. hook

use std::ops::Deref;

// For better performance, we recommend using AutoSafeHookManuallyDrop instead 
// of AlwaysSafeHookManuallyDrop. The AutoSafeHookManuallyDrop type depends on 
// the type of build, debug or release will be with the safe or insecure version
// of ManuallyDrop.
use SafeManuallyDrop::AlwaysSafeHookManuallyDrop as ManuallyDrop;

fn main() {
	unsafe {
		ManuallyDrop::set_hook(|args| {
			println!("!!!{:?}", args);
			
			for _ in 0..3 {
				std::thread::sleep(std::time::Duration::from_millis(1000));
			}
			
			println!("exit");
			std::process::exit(0x0100);
		});
	}
	
	let mut data = ManuallyDrop::new(vec![1, 2, 3, 4]);
	println!("data: {:?}", data.deref());
	
	#[allow(unused_unsafe)] // to avoid warning if the always_compatible_stdapi flag is not used (can be removed)
	unsafe {
		assert_eq!(data.is_next_trig(), false); // VALID
		ManuallyDrop::drop(&mut data); // VALID
		assert_eq!(data.is_next_trig(), true); // VALID
		
		// <<-- HOOK
		ManuallyDrop::drop(&mut data); // INVALID, COMBO DROP
	}
}

3. counter

// Let me remind you that CounterManuallyDrop by behavior allows undefined 
// behavior in the same way as ManuallyDrop, but, unlike ManuallyDrop, 
// Counter keeps a counter of the number of undefined behavior triggers.

// !!!!
// CounterManuallyDrop is experimental and changes the behavior of 
// the trigger trait for all types.

#[cfg(feature = "support_count_trig")]
use SafeManuallyDrop::AutoSafeCounterManuallyDrop as ManuallyDrop;

#[cfg(not(feature = "support_count_trig"))]
use SafeManuallyDrop::ManuallyDrop;

use std::ops::Deref;

#[allow(unreachable_code)]
fn main() {
	#[cfg(not(feature = "support_count_trig"))] {
		println!("To run the example, a build with feature: support_count_trig is required,");
		println!("exp: cargo run --example counter --all-features");
		println!("end.");
		
		return;
	}
	
	let mut data = ManuallyDrop::new(&[1, 2, 3, 4]);
	println!("data: {:?}", data.deref());
	
	#[allow(unused_unsafe)] // feature !always_compatible_stdapi
	unsafe {
		assert_eq!(data.is_next_trig(), false); // VALID, triggers never fired
		
		// =================
		// !!! ATTENTION !!!
		// =================
		// Procedure:
		// 1. Free up memory and try to read it
		// 2. Re-free memory
		ManuallyDrop::drop(&mut data); // VALID
		assert_eq!(data.is_next_trig(), true); // VALID, counter trigger worked.
		
		ManuallyDrop::drop(&mut data); // <<-- INVALID BEH, COUNTER += 1 (=1), COMBO DROP
	}
	
	// !!! Reading an already freed value
	println!("data: {:?}", &data); // <<-- INVALID BEH, COUNTER += 1 (=2)
	
	#[allow(unused_unsafe)] // to avoid warning if the always_compatible_stdapi flag is not used (can be removed)
	let _data2 = unsafe { // <<-- INVALID BEH, COUNTER += 1 (=3)
		// !!! Trying to get the freed value
		ManuallyDrop::take(&mut data)
	};
	
	#[cfg(feature = "support_count_trig")]
	assert_eq!(ManuallyDrop::get_count_trig_events(), 3); // <-- The number of times the undefined behavior was triggered.
}

cargo.toml -> features

// Flags:
//
	
// ManuallyDrop and AutoManuallyDrop are always type safe and are automatically 
// checked on use if the debug_assertions flag is enabled (the flag is automatically 
// enabled if test build, debug build, or env: CARGO_PROFILE_RELEASE_DEBUG_ASSERTIONS=true).
//
// (Also, AlwaysSafeManuallyDrop is always checked for safety when it is used, regardless of the flags.)
"always_check_in_case_debug_assertions", 

// ManuallyDrop and AutoManuallyDrop are always checked when used, 
// regardless of external flags.
//
// (Also, AlwaysSafeManuallyDrop is always checked for safety when it is used, regardless of the flags.)
// "always_safe_manuallydrop",

// Enable additional internal checks of the SafeManuallyDrop library when 
// the debug_assertions flag is enabled (does not depend on the always_check_in_case_debug_assertions 
// and always_safe_manuallydrop options). This flag type only applies to internal 
// library function checks, it is independent of ManuallyDrop and its valid or invalid usage.
//
// "allow_fullinternal_debug_assertions",

// Preserve unsafe fn flags even if functions are safe 
// (may be required for additional compatibility with the standard API)
"always_compatible_stdapi",

// Always create a modular table of library flags used in the build.
// (crate::core::flags)
"always_build_flagstable",

// Trigs:
//

// Ability to determine if an empty loop trigger has been executed.
"support_istrig_loop",

// Support for PanicManuallyDrop, in case of undefined behavior 
// of PanicManuallyDrop there will be a panic.
"support_panic_trig", 

// HookManuallyDrop support, in case of undefined HookManuallyDrop behavior, 
// the hook function will be called.
"support_hookfn_trig",

// Support for CounterManuallyDrop, in case of undefined behavior, 
// CounterManuallyDrop will add +1 to the counter.
//"support_count_trig",

// The behavior for the simple AutoSafeManuallyDrop/AlwaysSafeManuallyDrop/ManuallyDrop type will always 
// cause a panic in case of undefined behavior.
//"always_deftrig_panic",

// The behavior for the simple AutoSafeManuallyDrop/AlwaysSafeManuallyDrop/ManuallyDrop type will always 
// call the hook function in case of undefined behavior.
//"always_deftrig_hookfn",

// The behavior for the simple AutoSafeManuallyDrop/AlwaysSafeManuallyDrop/ManuallyDrop type will always call 
// the +1 counter function in case of undefined behavior.
//"always_deftrig_count",

// The behavior for the simple type AutoSafeManuallyDrop/AlwaysSafeManuallyDrop/ManuallyDrop will always call 
// the eternal loop function in case of undefined behavior.
//"always_deftrig_loop"

// INFO:
// If the behavior for the general AutoSafeManuallyDrop/AlwaysSafeManuallyDrop/ManuallyDrop is not fixed, 
// the behavior will be determined according to the following scheme:
//
//	always_deftrig_panic not exists AND
//	always_deftrig_hookfn not exists AND
//	always_deftrig_count not exists AND
//	always_deftrig_loop not exists THEN
//
//	support_hookfn_trig -> Hook,	else:
//	support_panic_trig -> Panic,	else:
//	support_count_trig -> Count,	else:
//		Loop
//

License

Copyright 2022 #UlinProject Denis Kotlyarov (Денис Котляров)

Licensed under the Apache License, Version 2.0