Awesome  Rust

Awesome Rust

1658819520

Jakt: A Memory-safe Systems Programming Language Built on Rust & C++

The Jakt programming language

Jakt is a memory-safe systems programming language.

It currently transpiles to C++.

NOTE: The language is under heavy development.

Usage

The transpilation to C++ requires clang. Make sure you have that installed.

jakt file.jakt
./build/file

Goals

  1. Memory safety
  2. Code readability
  3. Developer productivity
  4. Executable performance
  5. Fun!

Memory safety

The following strategies are employed to achieve memory safety:

  • Automatic reference counting
  • Strong typing
  • Bounds checking
  • No raw pointers in safe mode

In Jakt, there are three pointer types:

  •  T (Strong pointer to reference-counted class T.)
  •  weak T? (Weak pointer to reference-counted class T. Becomes empty on pointee destruction.)
  •  raw T (Raw pointer to arbitrary type T. Only usable in unsafe blocks.)

Null pointers are not possible in safe mode, but pointers can be wrapped in Optional, i.e Optional<T> or T? for short.

Note that weak pointers must always be wrapped in Optional. There is no weak T, only weak T?.

Math safety

  •  Integer overflow (both signed and unsigned) is a runtime error.
  •  Numeric values are not automatically coerced to int. All casts must be explicit.

For cases where silent integer overflow is desired, there are explicit functions that provide this functionality.

Code readability

Far more time is spent reading code than writing it. For that reason, Jakt puts a high emphasis on readability.

Some of the features that encourage more readable programs:

  •  Immutable by default.
  •  Argument labels in call expressions (object.function(width: 10, height: 5))
  •  Inferred enum scope. (You can say Foo instead of MyEnum::Foo).
  •  Pattern matching with match.
  •  Optional chaining (foo?.bar?.baz (fallible) and foo!.bar!.baz (infallible))
  •  None coalescing for optionals (foo ?? bar yields foo if foo has a value, otherwise bar)
  •  defer statements.
  •  Pointers are always dereferenced with . (never ->)
  •  Trailing closure parameters can be passed outside the call parentheses.
  •  Error propagation with ErrorOr<T> return type and dedicated try / must keywords.

Function calls

When calling a function, you must specify the name of each argument as you're passing it:

rect.set_size(width: 640, height: 480)

There are two exceptions to this:

  •  If the parameter in the function declaration is declared as anon, omitting the argument label is allowed.
  •  When passing a variable with the same name as the parameter.

Structures and classes

There are two main ways to declare a structure in Jakt: struct and class.

struct

Basic syntax:

struct Point {
    x: i64
    y: i64
}

Structs in Jakt have value semantics:

  • Variables that contain a struct always have a unique instance of the struct.
  • Copying a struct instance always makes a deep copy.
let a = Point(x: 10, y: 5)
let b = a
// "b" is a deep copy of "a", they do not refer to the same Point

Jakt generates a default constructor for structs. It takes all fields by name. For the Point struct above, it looks like this:

Point(x: i64, y: i64)

Struct members are public by default.

class

  •  basic class support
  •  private-by-default members
  •  inheritance
  •  class-based polymorphism (assign child instance to things requiring the parent type)
  •  Super type
  •  Self type

Same basic syntax as struct:

class Size {
    width: i64
    height: i64

    public function area(this) => .width * .height
}

Classes in Jakt have reference semantics:

  • Copying a class instance (aka an "object") copies a reference to the object.
  • All objects are reference-counted by default. This ensures that objects don't get accessed after being deleted.

Class members are private by default.

Member functions

Both structs and classes can have member functions.

There are three kinds of member functions:

Static member functions don't require an object to call. They have no this parameter.

class Foo {
    function func() => println("Hello!")
}

// Foo::func() can be called without an object.
Foo::func()

Non-mutating member functions require an object to be called, but cannot mutate the object. The first parameter is this.

class Foo {
    function func(this) => println("Hello!")
}

// Foo::func() can only be called on an instance of Foo.
let x = Foo()
x.func()

Mutating member functions require an object to be called, and may modify the object. The first parameter is mut this.

class Foo {
    x: i64

    function set(mut this, anon x: i64) {
        this.x = x
    }
}

// Foo::set() can only be called on a mut Foo:
mut foo = Foo(x: 3)
foo.set(9)

Shorthand for accessing member variables

To reduce repetitive this. spam in methods, the shorthand .foo expands to this.foo.

Arrays

Dynamic arrays are provided via a built-in Array<T> type. They can grow and shrink at runtime.

Array is memory safe:

  • Out-of-bounds will panic the program with a runtime error.
  • Slices of an Array keep the underlying data alive via automatic reference counting.

Declaring arrays

// Function that takes an Array<i64> and returns an Array<String>
function foo(numbers: [i64]) -> [String] {
    ...
}

Shorthand for creating arrays

// Array<i64> with 256 elements, all initialized to 0.
let values = [0; 256]

// Array<String> with 3 elements: "foo", "bar" and "baz".
let values = ["foo", "bar", "baz"]

Dictionaries

  •  Creating dictionaries
  •  Indexing dictionaries
  •  Assigning into indexes (aka lvalue)
function main() {
    let dict = ["a": 1, "b": 2]

    println("{}", dict["a"])
}

Declaring dictionaries

// Function that takes a Dictionary<i64, String> and returns an Dictionary<String, bool>
function foo(numbers: [i64:String]) -> [String:bool] {
    ...
}

Shorthand for creating dictionaries

// Dictionary<String, i64> with 3 entries.
let values = ["foo": 500, "bar": 600, "baz": 700]

Sets

  •  Creating sets
  •  Reference semantics
function main() {
    let set = {1, 2, 3}

    println("{}", set.contains(1))
    println("{}", set.contains(5))
}

Tuples

  •  Creating tuples
  •  Index tuples
  •  Tuple types
function main() {
    let x = ("a", 2, true)

    println("{}", x.1)
}

Enums and Pattern Matching

  •  Enums as sum-types
  •  Generic enums
  •  Enums as names for values of an underlying type
  •  match expressions
  •  Enum scope inference in match arms
  •  Yielding values from match blocks
  •  Nested match patterns
  •  Traits as match patterns
  •  Support for interop with the ?, ?? and ! operators
enum MyOptional<T> {
    Some(T)
    None
}

function value_or_default<T>(anon x: MyOptional<T>, default: T) -> T {
    return match x {
        Some(value) => {
            let stuff = maybe_do_stuff_with(value)
            let more_stuff = stuff.do_some_more_processing()
            yield more_stuff
        }
        None => default
    }
}

enum Foo {
    StructLikeThingy (
        field_a: i32
        field_b: i32
    )
}

function look_at_foo(anon x: Foo) -> i32 {
    match x {
        StructLikeThingy(field_a: a, field_b) => {
            return a + field_b
        }
    }
}

enum AlertDescription: i8 {
    CloseNotify = 0
    UnexpectedMessage = 10
    BadRecordMAC = 20
    // etc
}

// Use in match:
function do_nothing_in_particular() => match AlertDescription::CloseNotify {
    CloseNotify => { ... }
    UnexpectedMessage => { ... }
    BadRecordMAC => { ... }
}

Generics

  •  Generic types
  •  Generic type inference
  •  Traits

Jakt supports both generic structures and generic functions.

function id<T>(anon x: T) -> T {
    return x
}

function main() {
    let y = id(3)

    println("{}", y + 1000)
}
struct Foo<T> {
    x: T
}

function main() {
    let f = Foo(x: 100)

    println("{}", f.x)
}

Namespaces

  •  Namespace support for functions and struct/class/enum
  •  Deep namespace support
namespace Greeters {
    function greet() {
        println("Well, hello friends")
    }
}

function main() {
    Greeters::greet()
}

Type casts

There are two built-in casting operators in Jakt.

  • as? T: Returns an Optional<T>, empty if the source value isn't convertible to T.
  • as! T: Returns a T, aborts the program if the source value isn't convertible to T.

The as cast can do these things (note that the implementation may not agree yet):

  • Casts to the same type are infallible and pointless, so might be forbidden in the future.
  • If both types are primitive, a safe conversion is done.
    • Integer casts will fail if the value is out of range. This means that promotion casts like i32 -> i64 are infallible.
    • Float -> Integer casts truncate the decimal point (?)
    • Integer -> Float casts resolve to the closest value to the integer representable by the floating-point type (?). If the integer value is too large, they resolve to infinity (?)
    • Any primitive -> bool will create true for any value except 0, which is false.
    • bool -> any primitive will do false -> 0 and true -> 1, even for floats.
  • If the types are two different pointer types (see above), the cast is essentially a no-op. A cast to T will increment the reference count as expected; that's the preferred way of creating a strong reference from a weak reference. A cast from and to raw T is unsafe.
  • If the types are part of the same type hierarchy (i.e. one is a child type of another):
    • A child can be cast to its parent infallibly.
    • A parent can be cast to a child, but this will check the type at runtime and fail if the object was not of the child type or one of its subtypes.
  • If the types are incompatible, a user-defined cast is attempted to be used. The details here are not decided yet.
  • If nothing works, the cast will not even compile.

Additional casts are available in the standard library. Two important ones are as_saturated and as_truncated, which cast integral values while saturating to the boundaries or truncating bits, respectively.

Traits

(Not yet implemented)

To make generics a bit more powerful and expressive, you can add additional information to them:

trait Hashable {
    function hash(self) -> i128
}

class Foo implements Hashable {
    function hash(self) => 42
}

type i64 implements Hashable {
    function hash(self) => 100
}

The intention is that generics use traits to limit what is passed into a generic parameter, and also to grant that variable more capabilities in the body. It's not really intended to do vtable types of things (for that, just use a subclass)

Safety analysis

(Not yet implemented)

To keep things safe, there are a few kinds of analysis we'd like to do (non-exhaustive):

  • Preventing overlapping of method calls that would collide with each other. For example, creating an iterator over a container, and while that's live, resizing the container
  • Using and manipulating raw pointers
  • Calling out to C code that may have side effects

Error handling

Functions that can fail with an error instead of returning normally are marked with the throws keyword:

function task_that_might_fail() throws -> usize {
    if problem {
        throw Error::from_errno(EPROBLEM)
    }
    ...
    return result
}

function task_that_cannot_fail() -> usize {
    ...
    return result
}

Unlike languages like C++ and Java, errors don't unwind the call stack automatically. Instead, they bubble up to the nearest caller.

If nothing else is specified, calling a function that throws from within a function that throws will implicitly bubble errors.

Syntax for catching errors

If you want to catch errors locally instead of letting them bubble up to the caller, use a try/catch construct like this:

try {
    task_that_might_fail()
} catch error {
    println("Caught error: {}", error)
}

There's also a shorter form:

try task_that_might_fail() catch error {
    println("Caught error: {}", error)
}

Rethrowing errors

(Not yet implemented)

Inline C++

For better interoperability with existing C++ code, as well as situations where the capabilities of Jakt within unsafe blocks are not powerful enough, the possibility of embedding inline C++ code into the program exists in the form of cpp blocks:

mut x = 0
unsafe {
    cpp {
        "x = (i64)&x;"
    }
}
println("{}", x)

References

Values and objects can be passed by reference in some situations where it's provably safe to do so.

A reference is either immutable (default) or mutable.

Reference type syntax

  • &T is an immutable reference to a value of type T.
  • &mut T is a mutable reference to a value of type T.

Reference expression syntax

  • &foo creates an immutable reference to the variable foo.
  • &mut foo creates a mutable reference to the variable foo.

Dereferencing a reference

To "get the value out" of a reference, it must be dereferenced using the * operator:

function sum(a: &i64, b: &i64) -> i64 {
    return *a + *b
}

For mutable references to structs, you'll need to wrap the dereference in parentheses in order to do a field access:

struct Foo {
    x: i64
}
function zero_out(foo: &mut Foo) {
    (*foo).x = 0
}

References (first version) feature list:

  •  Reference types
  •  Reference function parameters
  •  No reference locals
  •  No references in structs
  •  No references in return types
  •  No mutable references to immutable values
  •  Allow &foo and &mut foo without argument label for parameters named foo

References TODO:

  •  (unsafe) references and raw pointers bidirectionally convertible
  •  No capture-by-reference in persistent closures

Download details:
Author: SerenityOS
Source code: https://github.com/SerenityOS/jakt
License: BSD-2-Clause license

#rust #rustlang

What is GEEK

Buddha Community

Jakt: A Memory-safe Systems Programming Language Built on Rust & C++
Ananya Gupta

Ananya Gupta

1594464365

Advantage of C Language Certification Online Training in 2020

C language is a procedural programming language. C language is the general purpose and object oriented programming language. C language is mainly used for developing different types of operating systems and other programming languages. C language is basically run in hardware and operating systems. C language is used many software applications such as internet browser, MYSQL and Microsoft Office.
**
Advantage of doing C Language Training in 2020 are:**

  1. Popular Programming language: The main Advantage of doing C language training in 2020 is popular programming language. C programming language is used and applied worldwide. C language is adaptable and flexible in nature. C language is important for different programmers. The basic languages that are used in C language is Java, C++, PHP, Python, Perl, JavaScript, Rust and C- shell.

  2. Basic language of all advanced languages: The another main Advantage of doing C language training in 2020 is basic language of all advanced languages. C language is an object oriented language. For learning, other languages, you have to master in C language.

  3. Understand the computer theories: The another main Advantage of doing C language training in 2020 is understand the computer theories. The theories such as Computer Networks, Computer Architecture and Operating Systems are based on C programming language.

  4. Fast in execution time: The another main Advantage of doing C language training in 2020 is fast in execution time. C language is to requires small run time and fast in execution time. The programs are written in C language are faster than the other programming language.

  5. Used by long term: The another main Advantage of doing C language training in 2020 is used by long term. The C language is not learning in the short span of time. It takes time and energy for becoming career in C language. C language is the only language that used by decades of time. C language is that exists for the longest period of time in computer programming history.

  6. Rich Function Library: The another main Advantage of doing C language training in 2020 is rich function library. C language has rich function of libraries as compared to other programming languages. The libraries help to build the analytical skills.

  7. Great degree of portability: The another main Advantage of doing C language training in 2020 is great degree of portability. C is a portable assemble language. It has a great degree of portability as compilers and interpreters of other programming languages are implemented in C language.
    The demand of C language is high in IT sector and increasing rapidly.

C Language Online Training is for individuals and professionals.
C Language Online Training helps to develop an application, build operating systems, games and applications, work on the accessibility of files and memory and many more.

C Language Online Course is providing the depth knowledge of functional and logical part, develop an application, work on memory management, understanding of line arguments, compiling, running and debugging of C programs.

Is C Language Training Worth Learning for You! and is providing the basic understanding of create C applications, apply the real time programming, write high quality code, computer programming, C functions, variables, datatypes, operators, loops, statements, groups, arrays, strings, etc.

The companies which are using C language are Amazon, Martin, Apple, Samsung, Google, Oracle, Nokia, IBM, Intel, Novell, Microsoft, Facebook, Bloomberg, VM Ware, etc.
C language is used in different domains like banking, IT, Insurance, Education, Gaming, Networking, Firmware, Telecommunication, Graphics, Management, Embedded, Application Development, Driver level Development, Banking, etc.

The job opportunities after completing the C Language Online certificationAre Data Scientists, Back End Developer, Embedded Developer, C Analyst, Software Developer, Junior Programmer, Database Developer, Embedded Engineer, Programming Architect, Game Programmer, Quality Analyst, Senior Programmer, Full Stack Developer, DevOps Specialist, Front End Web Developer, App Developer, Java Software Engineer, Software Developer and many more.

#c language online training #c language online course #c language certification online #c language certification #c language certification course #c language certification training

Ananya Gupta

Ananya Gupta

1599550659

Benefits Of C Language Over Other Programming Languages

C may be a middle-level programing language developed by Dennis Ritchie during the first 1970s while performing at AT&T Bell Labs within the USA. the target of its development was within the context of the re-design of the UNIX OS to enable it to be used on multiple computers.

Earlier the language B was now used for improving the UNIX. Being an application-oriented language, B allowed a much faster production of code than in programming language. Still, B suffered from drawbacks because it didn’t understand data-types and didn’t provide the utilization of “structures”.

These drawbacks became the drive for Ritchie for the development of a replacement programing language called C. He kept most of the language B’s syntax and added data-types and lots of other required changes. Eventually, C was developed during 1971-73, containing both high-level functionality and therefore the detailed features required to program an OS. Hence, many of the UNIX components including the UNIX kernel itself were eventually rewritten in C.

Benefits of C language

As a middle-level language, C combines the features of both high-level and low-level languages. It is often used for low-level programmings, like scripting for it also supports functions of high-level C programming languages, like scripting for software applications, etc.
C may be a structured programing language that allows a posh program to be broken into simpler programs called functions. It also allows free movement of knowledge across these functions.

Various features of C including direct access to machine level hardware APIs, the presence of C compilers, deterministic resource use, and dynamic memory allocation make C language an optimum choice for scripting applications and drivers of embedded systems.

C language is case-sensitive which suggests lowercase and uppercase letters are treated differently.
C is very portable and is employed for scripting system applications which form a serious a part of Windows, UNIX, and Linux OS.

C may be a general-purpose programing language and may efficiently work on enterprise applications, games, graphics, and applications requiring calculations, etc.
C language features a rich library that provides a variety of built-in functions. It also offers dynamic memory allocation.

C implements algorithms and data structures swiftly, facilitating faster computations in programs. This has enabled the utilization of C in applications requiring higher degrees of calculations like MATLAB and Mathematica.

Riding on these advantages, C became dominant and spread quickly beyond Bell Labs replacing many well-known languages of that point, like ALGOL, B, PL/I, FORTRAN, etc. C language has become available on a really wide selection of platforms, from embedded microcontrollers to supercomputers.

#c language online training #c language training #c language course #c language online course #c language certification course

Anil  Sakhiya

Anil Sakhiya

1607339640

C programming for Beginners | Learn C Programming | C Language

C Language is an evergreen language and is used widely across different industries, This C programming is a must for students and working professionals to become a great Software Engineer especially when they are working in Software Development Domain. Great Learning brings you this live session on “Introduction to C”. In this live session, we will be covering major concepts in C Programming such as Different Variables, Different Data Types that are being used, its Operators, Flow control statements, Structure, and lot more.

#c #programming #developer #c-programming #c-language

Abdullah  Kozey

Abdullah Kozey

1626250440

Using WebAssembly threads from C, C++ and Rust

WebAssembly threads support is one of the most important performance additions to WebAssembly. It allows you to either run parts of your code in parallel on separate cores, or the same code over independent parts of the input data, scaling it to as many cores as the user has and significantly reducing the overall execution time.

In this article you will learn how to use WebAssembly threads to bring multithreaded applications written in languages like C, C++, and Rust to the web.

How WebAssembly threads work #

WebAssembly threads is not a separate feature, but a combination of several components that allows WebAssembly apps to use traditional multithreading paradigms on the web.

Web Workers #

First component is the regular Workers you know and love from JavaScript. WebAssembly threads use the new Worker constructor to create new underlying threads. Each thread loads a JavaScript glue, and then the main thread uses Worker#postMessage method to share the compiled WebAssembly.Module as well as a shared WebAssembly.Memory (see below) with those other threads. This establishes communication and allows all those threads to run the same WebAssembly code on the same shared memory without going through JavaScript again.

Web Workers have been around for over a decade now, are widely supported, and don’t require any special flags.

SharedArrayBuffer #

WebAssembly memory is represented by a WebAssembly.Memory object in the JavaScript API. By default WebAssembly.Memory is a wrapper around an ArrayBuffer—a raw byte buffer that can be accessed only by a single thread.

> new WebAssembly.Memory({ initial:1, maximum:10 }).buffer
ArrayBuffer { … }

To support multithreading, WebAssembly.Memory gained a shared variant too. When created with a shared flag via the JavaScript API, or by the WebAssembly binary itself, it becomes a wrapper around a SharedArrayBuffer instead. It’s a variation of ArrayBuffer that can be shared with other threads and read or modified simultaneously from either side.

> new WebAssembly.Memory({ initial:1, maximum:10, shared:true }).buffer
SharedArrayBuffer { … }

Unlike postMessage, normally used for communication between main thread and Web Workers, SharedArrayBuffer doesn’t require copying data or even waiting for the event loop to send and receive messages. Instead, any changes are seen by all threads nearly instantly, which makes it a much better compilation target for traditional synchronisation primitives.

SharedArrayBuffer has a complicated history. It was initially shipped in several browsers mid-2017, but had to be disabled in the beginning of 2018 due to discovery of Spectre vulnerabilities. The particular reason was that data extraction in Spectre relies on timing attacks—measuring execution time of a particular piece of code. To make this kind of attack harder, browsers reduced precision of standard timing APIs like Date.now and performance.now. However, shared memory, combined with a simple counter loop running in a separate thread is also a very reliable way to get high-precision timing, and it’s much harder to mitigate without significantly throttling runtime performance.

Instead, Chrome 68 (mid-2018) re-enabled SharedArrayBuffer again by leveraging Site Isolation—a feature that puts different websites into different processes and makes it much more difficult to use side-channel attacks like Spectre. However, this mitigation was still limited only to Chrome desktop, as Site Isolation is a fairly expensive feature, and couldn’t be enabled by default for all sites on low-memory mobile devices nor was it yet implemented by other vendors.

Fast-forward to 2020, Chrome and Firefox both have implementations of Site Isolation, and a standard way for websites to opt-in to the feature with COOP and COEP headers. An opt-in mechanism allows to use Site Isolation even on low-powered devices where enabling it for all the websites would be too expensive. To opt-in, add the following headers to the main document in your server configuration:

Cross-Origin-Embedder-Policy: require-corp
Cross-Origin-Opener-Policy: same-origin

Once you opt-in, you get access to SharedArrayBuffer (including WebAssembly.Memory backed by a SharedArrayBuffer), precise timers, memory measurement and other APIs that require an isolated origin for security reasons. Check out the Making your website “cross-origin isolated” using COOP and COEP for more details.

WebAssembly atomics #

While SharedArrayBuffer allows each thread to read and write to the same memory, for correct communication you want to make sure they don’t perform conflicting operations at the same time. For example, it’s possible for one thread to start reading data from a shared address, while another thread is writing to it, so the first thread will now get a corrupted result. This category of bugs is known as race conditions. In order to prevent race conditions, you need to somehow synchronize those accesses. This is where atomic operations come in.

WebAssembly atomics is an extension to the WebAssembly instruction set that allow to read and write small cells of data (usually 32- and 64-bit integers) “atomically”. That is, in a way that guarantees that no two threads are reading or writing to the same cell at the same time, preventing such conflicts at a low level. Additionally, WebAssembly atomics contain two more instruction kinds—“wait” and “notify”—that allow one thread to sleep (“wait”) on a given address in a shared memory until another thread wakes it up via “notify”.

  • All the higher-level synchronisation primitives, including channels, mutexes, and read-write locks build upon those instructions.

#rust #c, c++ #cplusplus #c++ #c #rust programming

Abdullah  Kozey

Abdullah Kozey

1617695702

Learning C: Input and Output and Two Program Templates

Before I get too deep into C, I need to show you how to get data into and out of your programs. Using assignment for data gets old after a while and you want to be able to have users enter their own data. And you definitely need to be able to see what happens to your data in a program so learning how to display data to the screen is important and necessary.

Besides demonstrating how to perform input and output in C, I will also be demonstrating two templates that are related to those topics — Prompt, Then Read and Input, Process, Output (IPO). The IPO template, in particular, is important because practically every C program you write will use this template.

When I talk about input and output in C, I’ll use the terms standard input and standard output. These terms refer to the default input and output devices on your computer. The standard input device is the keyboard. The standard output device is the computer’s monitor or screen. I will only use the terms input and output and when I use those terms I’m referring to standard input and standard output. If I want to refer to a different device for input and/or output, I’ll use the specific term for that device.

#c-programming-language #c-programming #c-program #c-programming-help