golang数组内存分配原理

var arr1 [3]int
var arr2 = [3]int{1,2,3}
arr3 := [...]int{1,2,3}

// go/src/cmd/compile/internal/syntax/parser.go
func (p *parser) typeOrNil() Expr {
  ...
    pos := p.pos()
    switch p.tok {
    ...
    case _Lbrack:
        // '[' oexpr ']' ntype
        // '[' _DotDotDot ']' ntype
        p.next()
        if p.got(_Rbrack) {
            return p.sliceType(pos)
        }
        return p.arrayType(pos, nil)
  ...
}
// "[" has already been consumed, and pos is its position.
// If len != nil it is the already consumed array length.
func (p *parser) arrayType(pos Pos, len Expr) Expr {
    ...
    if len == nil && !p.got(_DotDotDot) {
        p.xnest++
        len = p.expr()
        p.xnest--
    }
    ...
    p.want(_Rbrack)
    t := new(ArrayType)
    t.pos = pos
    t.Len = len
    t.Elem = p.type_()
    return t
}

// go/src/cmd/compile/internal/syntax/nodes.go
type (
  ...
    // [Len]Elem
    ArrayType struct {
        Len  Expr // nil means Len is ...
        Elem Expr
        expr
    }
  ...
)

// go/src/cmd/compile/internal/types2/array.go
// An Array represents an array type.
type Array struct {
    len  int64
    elem Type
}

// go/src/cmd/compile/internal/types2/expr.go
// exprInternal contains the core of type checking of expressions.
// Must only be called by rawExpr.
func (check *Checker) exprInternal(x *operand, e syntax.Expr, hint Type) exprKind {
    ...
    switch e := e.(type) {
    ...
    case *syntax.CompositeLit:
        var typ, base Type

        switch {
        case e.Type != nil:
            // composite literal type present - use it
            // [...]T array types may only appear with composite literals.
            // Check for them here so we don't have to handle ... in general.
            if atyp, _ := e.Type.(*syntax.ArrayType); atyp != nil && atyp.Len == nil {
                // We have an "open" [...]T array type.
                // Create a new ArrayType with unknown length (-1)
                // and finish setting it up after analyzing the literal.
                typ = &Array{len: -1, elem: check.varType(atyp.Elem)}
                base = typ
                break
            }
            typ = check.typ(e.Type)
            base = typ
      ...
        }

        switch utyp := coreType(base).(type) {
        ...
        case *Array:
            if utyp.elem == nil {
                check.error(e, "illegal cycle in type declaration")
                goto Error
            }
            n := check.indexedElts(e.ElemList, utyp.elem, utyp.len)
            // If we have an array of unknown length (usually [...]T arrays, but also
            // arrays [n]T where n is invalid) set the length now that we know it and
            // record the type for the array (usually done by check.typ which is not
            // called for [...]T). We handle [...]T arrays and arrays with invalid
            // length the same here because it makes sense to "guess" the length for
            // the latter if we have a composite literal; e.g. for [n]int{1, 2, 3}
            // where n is invalid for some reason, it seems fair to assume it should
            // be 3 (see also Checked.arrayLength and issue #27346).
            if utyp.len < 0 {
                utyp.len = n
                // e.Type is missing if we have a composite literal element
                // that is itself a composite literal with omitted type. In
                // that case there is nothing to record (there is no type in
                // the source at that point).
                if e.Type != nil {
                    check.recordTypeAndValue(e.Type, typexpr, utyp, nil)
                }
            }
        ...
        }
    ...
}

// go/src/cmd/compile/internal/noder/types.go
// typ0 converts a types2.Type to a types.Type, but doesn't do the caching check
// at the top level.
func (g *irgen) typ0(typ types2.Type) *types.Type {
    switch typ := typ.(type) {
    ...
    case *types2.Array:
        return types.NewArray(g.typ1(typ.Elem()), typ.Len())
    ...
}

// go/src/cmd/compile/internal/types/type.go
// Array contains Type fields specific to array types.
type Array struct {
    Elem  *Type // element type
    Bound int64 // number of elements; <0 if unknown yet
}
// NewArray returns a new fixed-length array Type.
func NewArray(elem *Type, bound int64) *Type {
    if bound < 0 {
        base.Fatalf("NewArray: invalid bound %v", bound)
    }
    t := newType(TARRAY)
    t.extra = &Array{Elem: elem, Bound: bound}
    t.SetNotInHeap(elem.NotInHeap())
    if elem.HasTParam() {
        t.SetHasTParam(true)
    }
    if elem.HasShape() {
        t.SetHasShape(true)
    }
    return t
}

// go/src/cmd/compile/internal/typecheck/expr.go
func tcCompLit(n *ir.CompLitExpr) (res ir.Node) {
    ...
    t := n.Type()
    base.AssertfAt(t != nil, n.Pos(), "missing type in composite literal")

    switch t.Kind() {
    ...
    case types.TARRAY:
        typecheckarraylit(t.Elem(), t.NumElem(), n.List, "array literal")
        n.SetOp(ir.OARRAYLIT)
    ...

    return n
}

// go/src/cmd/compile/internal/typecheck/typecheck.go
// typecheckarraylit type-checks a sequence of slice/array literal elements.
func typecheckarraylit(elemType *types.Type, bound int64, elts []ir.Node, ctx string) int64 {
    ...
    for i, elt := range elts {
        ir.SetPos(elt)
        r := elts[i]
        ...
        r = Expr(r)
        r = AssignConv(r, elemType, ctx)
        ...
}

arr := [...]string{"s1", "s2", "s3"}
e3 := arr[3]
// invalid array index 3 (out of bounds for 3-element array)

// go/src/cmd/compile/internal/typecheck/typecheck.go
func typecheck1(n ir.Node, top int) ir.Node {
  ...
    switch n.Op() {
  ...
  case ir.OINDEX:
        n := n.(*ir.IndexExpr)
        return tcIndex(n)
  ...
  }
}
// go/src/cmd/compile/internal/typecheck/expr.go
func tcIndex(n *ir.IndexExpr) ir.Node {
    ...
    l := n.X
    n.Index = Expr(n.Index)
    r := n.Index
    t := l.Type()
    ...
    switch t.Kind() {
    ...
    case types.TSTRING, types.TARRAY, types.TSLICE:
        n.Index = indexlit(n.Index)
        if t.IsString() {
            n.SetType(types.ByteType)
        } else {
            n.SetType(t.Elem())
        }
        why := "string"
        if t.IsArray() {
            why = "array"
        } else if t.IsSlice() {
            why = "slice"
        }
        if n.Index.Type() != nil && !n.Index.Type().IsInteger() {
            base.Errorf("non-integer %s index %v", why, n.Index)
            return n
        }
        if !n.Bounded() && ir.IsConst(n.Index, constant.Int) {
            x := n.Index.Val()
            if constant.Sign(x) < 0 {
                base.Errorf("invalid %s index %v (index must be non-negative)", why, n.Index)
            } else if t.IsArray() && constant.Compare(x, token.GEQ, constant.MakeInt64(t.NumElem())) {
                base.Errorf("invalid array index %v (out of bounds for %d-element array)", n.Index, t.NumElem())
            } else if ir.IsConst(n.X, constant.String) && constant.Compare(x, token.GEQ, constant.MakeInt64(int64(len(ir.StringVal(n.X))))) {
                base.Errorf("invalid string index %v (out of bounds for %d-byte string)", n.Index, len(ir.StringVal(n.X)))
            } else if ir.ConstOverflow(x, types.Types[types.TINT]) {
                base.Errorf("invalid %s index %v (index too large)", why, n.Index)
            }
        }
    ...
    }
    return n
}

// go/src/runtime/malloc.go
// newarray allocates an array of n elements of type typ.
func newarray(typ *_type, n int) unsafe.Pointer {
    if n == 1 {
        return mallocgc(typ.size, typ, true)
    }
    mem, overflow := math.MulUintptr(typ.size, uintptr(n))
    if overflow || mem > maxAlloc || n < 0 {
        panic(plainError("runtime: allocation size out of range"))
    }
    return mallocgc(mem, typ, true)
}
// Allocate an object of size bytes.
// Small objects are allocated from the per-P cache's free lists.
// Large objects (> 32 kB) are allocated straight from the heap.
func mallocgc(size uintptr, typ *_type, needzero bool) unsafe.Pointer {
    ...
}

type Array struct {
  Elem  *Type // element type
  Bound int64 // number of elements; <0 if unknown yet
}