17 Byte Compilation

Emacs Lisp has a compiler that translates functions written in Lisp into a special representation called byte-code that can be executed more efficiently. The compiler replaces Lisp function definitions with byte-code. When a byte-code function is called, its definition is evaluated by the byte-code interpreter.

Because the byte-compiled code is evaluated by the byte-code interpreter, instead of being executed directly by the machine’s hardware (as true compiled code is), byte-code is completely transportable from machine to machine without recompilation. It is not, however, as fast as true compiled code.

In general, any version of Emacs can run byte-compiled code produced by recent earlier versions of Emacs, but the reverse is not true.

If you do not want a Lisp file to be compiled, ever, put a file-local variable binding for no-byte-compile into it, like this:

;; -*-no-byte-compile: t; -*-

• Speed of Byte-Code		An example of speedup from byte compilation.
• Compilation Functions		Byte compilation functions.
• Docs and Compilation		Dynamic loading of documentation strings.
• Dynamic Loading		Dynamic loading of individual functions.
• Eval During Compile		Code to be evaluated when you compile.
• Compiler Errors		Handling compiler error messages.
• Byte-Code Objects		The data type used for byte-compiled functions.
• Disassembly		Disassembling byte-code; how to read byte-code.