Programming Languages - Compilers and Runtimes
- runtime: some languages have big runtimes, or full virtual machines, like Java (JVM); some languages have small runtimes, just a library to provide critical functions, like
libcfor C, and
runtimelib for Go.
- GC refers to runtime GC; Swift has Automatic Reference Counting but at the compile time.
- In Go, GC is provided by the
- JVM (Java Virtual Machine): Java, Scala, Groovy, Kotlin
- Why Groovy is more Popular than Scala: Groovy is 100% Java compatible because it IS Java; take any Java class, change the extension to from '.java' to '.groovy' and it WILL compile (NOTE: one must have groovy library installed).
- CLR (Common Language Runtime): C#
- HHVM (HipHop Virtual Machine): PHP/Hack. HHVM JIT compilation, executed PHP or Hack code is first transformed into intermediate HipHop bytecode (HHBC), which is then dynamically translated into x86-64 machine code, optimized, and natively executed. This contrasts with PHP's usual interpreted execution, in which the Zend Engine transforms PHP source code into opcodes that serve as a form of bytecode, and executes the opcodes directly on the Zend Engine's virtual CPU.
- LLVM is the backend AND the umbrella project name.
- LLVM is NOT a traditional virtual machine.
- It is NOT an acronym (though originally it stands for Low Level Virtual Machine).
- It contains modularized compiler components and tool chains.
- Clang: frontend for C/C++/Object-C/Object-C++.
- Backend converts the LLVM Intermediate Representation (IR) to code for a specified machine or other languages (hardware OR software target)
AOT vs JIT
- static compiler, or ahead-of-time(AOT) compiler: at compile-time, e.g. from
- dynamic compiler, or just-in-time(JIT) compiler: at run-time, e.g. in Java, compiles bytecode to native instructions.
bytecode is portable, but native code is not.
Java JIT 2 flavors:
- client-side compiler(with
-clientoption): fewer resources, sensitive to startup time.
- server-side compiler(with
-serveroption): long running, more advanced optimizations.
Compiler vs Interpreter
A script is program code that doesn’t need pre-processing (e.g. compiling) before being run.
- compiled to standalone executables: C/C++, COBOL
- ran in an interpreter: Perl, Tcl
- Java need for both a bytecode compiler and a runtime interpreter.
- Python and R have no compile-time type-safety,