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Merge pull request #1247 from nspcc-dev/feature/pointers

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Support pointers in compiler
This commit is contained in:
Roman Khimov 2020-08-06 13:53:08 +03:00 committed by GitHub
commit e1d3223505
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3 changed files with 126 additions and 5 deletions
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2
docs/compiler.md
View file

@ -9,6 +9,8 @@ there are some important deviations that you need to be aware of that make it
a dialect of Go rather than a complete port of the language:
* `make()` ane `new()` are not supported, most of the time you can substitute
them with composite literals
* pointers are supported only for struct literals, one can't take an address
of an arbitrary variable
* there is no real distinction between different integer types, all of them
work as big.Int in Go with a limit of 256 bit in width, so you can use
`int` for just about anything. This is the way integers work in Neo VM and

61
pkg/compiler/codegen.go
View file

@ -465,7 +465,7 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
c.emitStoreVar(t.X.(*ast.Ident).Name, t.Sel.Name)
return nil
}
strct, ok := typ.Underlying().(*types.Struct)
strct, ok := c.getStruct(typ)
if !ok {
c.prog.Err = fmt.Errorf("nested selector assigns not supported yet")
return nil
@ -637,6 +637,16 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
c.emitLoadConst(c.typeAndValueOf(n))
return nil
case *ast.StarExpr:
_, ok := c.getStruct(c.typeOf(n.X))
if !ok {
c.prog.Err = errors.New("dereferencing is only supported on structs")
return nil
}
ast.Walk(c, n.X)
c.emitConvert(stackitem.StructT)
return nil
case *ast.Ident:
if tv := c.typeAndValueOf(n); tv.Value != nil {
c.emitLoadConst(tv)
@ -650,7 +660,7 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
case *ast.CompositeLit:
switch typ := c.typeOf(n).Underlying().(type) {
case *types.Struct:
c.convertStruct(n)
c.convertStruct(n, false)
case *types.Map:
c.convertMap(n)
default:
@ -810,6 +820,18 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
// Handle the arguments
for _, arg := range args {
ast.Walk(c, arg)
typ := c.typeOf(arg)
_, ok := typ.Underlying().(*types.Struct)
if ok && !isInteropPath(typ.String()) {
// To clone struct fields we create a new array and append struct to it.
// This way even non-pointer struct fields will be copied.
emit.Opcode(c.prog.BinWriter, opcode.NEWARRAY0)
emit.Opcode(c.prog.BinWriter, opcode.DUP)
emit.Opcode(c.prog.BinWriter, opcode.ROT)
emit.Opcode(c.prog.BinWriter, opcode.APPEND)
emit.Opcode(c.prog.BinWriter, opcode.PUSH0)
emit.Opcode(c.prog.BinWriter, opcode.PICKITEM)
}
}
// Do not swap for builtin functions.
if !isBuiltin {
@ -862,7 +884,7 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
}
return nil
}
strct, ok := typ.Underlying().(*types.Struct)
strct, ok := c.getStruct(typ)
if !ok {
c.prog.Err = fmt.Errorf("selectors are supported only on structs")
return nil
@ -873,6 +895,19 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
return nil
case *ast.UnaryExpr:
if n.Op == token.AND {
// We support only taking address from struct literals.
// For identifiers we can't support "taking address" in a general way
// because both struct and array are reference types.
lit, ok := n.X.(*ast.CompositeLit)
if ok {
c.convertStruct(lit, true)
return nil
}
c.prog.Err = fmt.Errorf("'&' can be used only with struct literals")
return nil
}
ast.Walk(c, n.X)
// From https://golang.org/ref/spec#Operators
// there can be only following unary operators
@ -1352,7 +1387,19 @@ func (c *codegen) convertMap(lit *ast.CompositeLit) {
}
}
func (c *codegen) convertStruct(lit *ast.CompositeLit) {
func (c *codegen) getStruct(typ types.Type) (*types.Struct, bool) {
switch t := typ.Underlying().(type) {
case *types.Struct:
return t, true
case *types.Pointer:
strct, ok := t.Elem().Underlying().(*types.Struct)
return strct, ok
default:
return nil, false
}
}
func (c *codegen) convertStruct(lit *ast.CompositeLit, ptr bool) {
// Create a new structScope to initialize and store
// the positions of its variables.
strct, ok := c.typeOf(lit).Underlying().(*types.Struct)
@ -1363,7 +1410,11 @@ func (c *codegen) convertStruct(lit *ast.CompositeLit) {
emit.Opcode(c.prog.BinWriter, opcode.NOP)
emit.Int(c.prog.BinWriter, int64(strct.NumFields()))
emit.Opcode(c.prog.BinWriter, opcode.NEWSTRUCT)
if ptr {
emit.Opcode(c.prog.BinWriter, opcode.NEWARRAY)
} else {
emit.Opcode(c.prog.BinWriter, opcode.NEWSTRUCT)
}
keyedLit := len(lit.Elts) > 0
if keyedLit {

68
pkg/compiler/pointer_test.go Normal file
View file

@ -0,0 +1,68 @@
package compiler_test
import (
"math/big"
"testing"
)
func TestAddressOfLiteral(t *testing.T) {
src := `package foo
type Foo struct { A int }
func Main() int {
f := &Foo{}
setA(f, 3)
return f.A
}
func setA(s *Foo, a int) { s.A = a }`
eval(t, src, big.NewInt(3))
}
func TestPointerDereference(t *testing.T) {
src := `package foo
type Foo struct { A int }
func Main() int {
f := &Foo{A: 4}
setA(*f, 3)
return f.A
}
func setA(s Foo, a int) { s.A = a }`
eval(t, src, big.NewInt(4))
}
func TestStructArgCopy(t *testing.T) {
t.Run("Simple", func(t *testing.T) {
src := `package foo
type Foo struct { A int }
func Main() int {
f := Foo{A: 4}
setA(f, 3)
return f.A
}
func setA(s Foo, a int) { s.A = a }`
eval(t, src, big.NewInt(4))
})
t.Run("StructField", func(t *testing.T) {
src := `package foo
type Bar struct { A int }
type Foo struct { B Bar }
func Main() int {
f := Foo{B: Bar{A: 4}}
setA(f, 3)
return f.B.A
}
func setA(s Foo, a int) { s.B.A = a }`
eval(t, src, big.NewInt(4))
})
t.Run("StructPointerField", func(t *testing.T) {
src := `package foo
type Bar struct { A int }
type Foo struct { B *Bar }
func Main() int {
f := Foo{B: &Bar{A: 4}}
setA(f, 3)
return f.B.A
}
func setA(s Foo, a int) { s.B.A = a }`
eval(t, src, big.NewInt(3))
})
}