The binary output of compiling to WebAssembly.
This has been done several times before, but doing it for oneself can be a very knowledge-yielding exercise and can assist in achieving a better understanding of WebAssembly in general.
(module
(func $printi (import "imports" "printi") (param i32))
(func $start
(local i32)
i32.const 5
i32.const 3
i32.add
set_local 0
get_local 0
call $printi
)
(start $start)
)Compiled to WASM (I added more details than wast2wasm -v would)
; Header
00 61 73 6D ; translates to '\0asm', WebAssembly's magic number. Is there for quick file type detection.
01 00 00 00 ; Version number (1)
; Section "Type" (1) - spec: required
01 ; Section code: 0x1 = Type
08 ; Section size: 0x8 bytes (the following 8 bytes are contained within this section)
02 ; Number of types in section: 2 types
; type #0
60 ; Type code: 0x60 = function
01 ; Number of params: 0x1
7F ; Param 1's type: 0x7F = i32
00 ; Number of results: 0x0
; type #1
60 ; Type code: 0x60 = function
00 ; Number of params: 0x0
00 ; Number of results: 0x0
; Section "Import" (2) - spec: optional
02 ; Section code: 0x2 = Import
12 ; Section size: 0x12 bytes (decimal: 18)
01 ; Number of imports: 0x1
; import header #0
07 ; String length: 0x7 bytes
69 6D 70 6F 72 74 73 ; Import module name: ascii => "imports"
06 ; String length: 0x6 bytes
70 72 69 6E 74 69 ; Import field name: ascii => "printi"
00 ; Import kind: 0x0 (using external_kinds table: 0 = function) https://github.com/WebAssembly/design/blob/master/BinaryEncoding.md#external_kind
00 ; Import signature index: 0x0 (referring to function signature at type #0)
; Section "Function" (3) - spec: required
03 ; Section code: 0x3 = Function
02 ; Section size: 0x2 bytes
01 ; Number of functions: 0x1
01 ; Function #0 signature index: 0x1 (refers to type #1)
; Section "Start" (8) - spec: optional
08 ; Section code: 0x8 = Start
01 ; Section size: 0x1 bytes
01 ; Start function index (refers to function #1)
; Section "Code" (10) - spec: required
0A ; Section code: 0xa = Code (decimal: 10)
11 ; Section size: 0x11 bytes (decimal: 17)
01 ; Number of functions: 0x1
0F ; Function body size: 0xf (decimal: 15)
01 ; Local variable declaration count: 0x1
01 ; Local type count of immediate type identifier: 0x1
7F ; Type identifier for i32
41 ; i32.const (the next opcode will be a literal)
05 ; i32 literal: 0x05
41 ; i32.const
03 ; i32 literal: 0x03
6A ; i32.add (pop two values from stack, and add them, push result onto stack)
21 ; set_local, take the next value pushed to the stack, and assign local at that index with stack pop value
00 ; local variable index: 0x0
20 ; get_local, take the next value pushed to the stack, and push local at that index onto stack
00 ; local variable index: 0x0
10 ; call function at index from next value pushed to stack
00 ; function index: 0x0
0B ; end