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cmd/compile: fixes for non-constant Sizeof/Alignof/Offsetof
Includes Robert's suggested fix in validate.go to not fail on non-constant alignof/offsetof/sizeof calls. Further changes to wait on transforming these calls until stenciling time, when we can call EvalConst() to evaluate them once all the relevant types are known. Added a bunch of new tests for non-constant Sizeof/Alignof/Offsetof. Fixes #47716 Change-Id: I469af888eb9ce3a853124d919eda753971009b3e Reviewed-on: https://go-review.googlesource.com/c/go/+/344250 Run-TryBot: Dan Scales <danscales@google.com> TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org> Trust: Dan Scales <danscales@google.com>
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@ -138,10 +138,18 @@ func Call(pos src.XPos, typ *types.Type, fun ir.Node, args []ir.Node, dots bool)
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// until arg type known
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// OAPPEND: transformAppend requires that the arg is a slice
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// ODELETE: transformDelete requires that the arg is a map
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// OALIGNOF, OSIZEOF: can be eval'ed to a constant until types known.
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switch fun.BuiltinOp {
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case ir.OMAKE, ir.OREAL, ir.OIMAG, ir.OAPPEND, ir.ODELETE:
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case ir.OMAKE, ir.OREAL, ir.OIMAG, ir.OAPPEND, ir.ODELETE, ir.OALIGNOF, ir.OOFFSETOF, ir.OSIZEOF:
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hasTParam := false
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for _, arg := range args {
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if fun.BuiltinOp == ir.OOFFSETOF {
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// It's the type of left operand of the
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// selection that matters, not the type of
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// the field itself (which is irrelevant for
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// offsetof).
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arg = arg.(*ir.SelectorExpr).X
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}
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if arg.Type().HasTParam() {
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hasTParam = true
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break
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@ -1037,7 +1037,7 @@ func (subst *subster) node(n ir.Node) ir.Node {
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name := call.X.Name()
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if name.BuiltinOp != ir.OXXX {
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switch name.BuiltinOp {
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case ir.OMAKE, ir.OREAL, ir.OIMAG, ir.OAPPEND, ir.ODELETE:
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case ir.OMAKE, ir.OREAL, ir.OIMAG, ir.OAPPEND, ir.ODELETE, ir.OALIGNOF, ir.OOFFSETOF, ir.OSIZEOF:
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// Transform these builtins now that we
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// know the type of the args.
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m = transformBuiltin(call)
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@ -811,7 +811,10 @@ func transformBuiltin(n *ir.CallExpr) ir.Node {
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return transformRealImag(u1.(*ir.UnaryExpr))
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case ir.OPANIC:
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return transformPanic(u1.(*ir.UnaryExpr))
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case ir.OCLOSE, ir.ONEW, ir.OALIGNOF, ir.OOFFSETOF, ir.OSIZEOF:
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case ir.OALIGNOF, ir.OOFFSETOF, ir.OSIZEOF:
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// This corresponds to the EvalConst() call near end of typecheck().
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return typecheck.EvalConst(u1)
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case ir.OCLOSE, ir.ONEW:
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// nothing more to do
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return u1
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}
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@ -81,7 +81,16 @@ func (g *irgen) validateBuiltin(name string, call *syntax.CallExpr) {
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// Check that types2+gcSizes calculates sizes the same
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// as cmd/compile does.
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got, ok := constant.Int64Val(g.info.Types[call].Value)
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tv := g.info.Types[call]
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if !tv.IsValue() {
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base.FatalfAt(g.pos(call), "expected a value")
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}
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if tv.Value == nil {
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break // unsafe op is not a constant, so no further validation
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}
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got, ok := constant.Int64Val(tv.Value)
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if !ok {
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base.FatalfAt(g.pos(call), "expected int64 constant value")
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}
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@ -881,7 +881,9 @@ func evalunsafe(n ir.Node) int64 {
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case ir.OOFFSETOF:
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// must be a selector.
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n := n.(*ir.UnaryExpr)
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if n.X.Op() != ir.OXDOT {
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// ODOT and ODOTPTR are allowed in case the OXDOT transformation has
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// already happened (e.g. during -G=3 stenciling).
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if n.X.Op() != ir.OXDOT && n.X.Op() != ir.ODOT && n.X.Op() != ir.ODOTPTR {
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base.Errorf("invalid expression %v", n)
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return 0
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}
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68
test/typeparam/issue47716.go
Normal file
68
test/typeparam/issue47716.go
Normal file
@ -0,0 +1,68 @@
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// run -gcflags=-G=3
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// Copyright 2021 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package main
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import (
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"fmt"
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"unsafe"
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)
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// size returns the size of type T
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func size[T any](x T) uintptr {
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return unsafe.Sizeof(x)
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}
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// size returns the alignment of type T
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func align[T any](x T) uintptr {
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return unsafe.Alignof(x)
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}
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type Tstruct[T any] struct {
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f1 T
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f2 int
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}
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// offset returns the offset of field f2 in the generic type Tstruct
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func (r *Tstruct[T]) offset() uintptr {
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return unsafe.Offsetof(r.f2)
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}
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func main() {
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v1 := int(5)
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if got, want := size(v1), unsafe.Sizeof(v1); got != want {
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panic(fmt.Sprintf("got %d, want %d", got, want))
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}
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if got, want := align(v1), unsafe.Alignof(v1); got != want {
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panic(fmt.Sprintf("got %d, want %d", got, want))
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}
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v2 := "abc"
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if got, want := size(v2), unsafe.Sizeof(v2); got != want {
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panic(fmt.Sprintf("got %d, want %d", got, want))
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}
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if got, want := align(v2), unsafe.Alignof(v2); got != want {
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panic(fmt.Sprintf("got %d, want %d", got, want))
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}
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var v3 Tstruct[int]
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if got, want := unsafe.Offsetof(v3.f2), unsafe.Sizeof(v1); got != want {
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panic(fmt.Sprintf("got %d, want %d", got, want))
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}
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var v4 Tstruct[interface{}]
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var v5 interface{}
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if got, want := unsafe.Offsetof(v4.f2), unsafe.Sizeof(v5); got != want {
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panic(fmt.Sprintf("got %d, want %d", got, want))
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}
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if got, want := v3.offset(), unsafe.Offsetof(v3.f2); got != want {
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panic(fmt.Sprintf("got %d, want %d", got, want))
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}
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if got, want := v4.offset(), unsafe.Offsetof(v4.f2); got != want {
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panic(fmt.Sprintf("got %d, want %d", got, want))
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}
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}
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