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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package gc
import (
"cmd/compile/internal/base"
"cmd/compile/internal/ir"
)
// evalunsafe evaluates a package unsafe operation and returns the result.
func evalunsafe(n ir.Node) int64 {
switch n.Op() {
case ir.OALIGNOF, ir.OSIZEOF:
n.SetLeft(typecheck(n.Left(), ctxExpr))
n.SetLeft(defaultlit(n.Left(), nil))
tr := n.Left().Type()
if tr == nil {
return 0
}
dowidth(tr)
if n.Op() == ir.OALIGNOF {
return int64(tr.Align)
}
return tr.Width
case ir.OOFFSETOF:
// must be a selector.
if n.Left().Op() != ir.OXDOT {
base.Errorf("invalid expression %v", n)
return 0
}
// Remember base of selector to find it back after dot insertion.
// Since r->left may be mutated by typechecking, check it explicitly
// first to track it correctly.
n.Left().SetLeft(typecheck(n.Left().Left(), ctxExpr))
sbase := n.Left().Left()
n.SetLeft(typecheck(n.Left(), ctxExpr))
if n.Left().Type() == nil {
return 0
}
switch n.Left().Op() {
case ir.ODOT, ir.ODOTPTR:
break
case ir.OCALLPART:
base.Errorf("invalid expression %v: argument is a method value", n)
return 0
default:
base.Errorf("invalid expression %v", n)
return 0
}
// Sum offsets for dots until we reach sbase.
var v int64
for r := n.Left(); r != sbase; r = r.Left() {
switch r.Op() {
case ir.ODOTPTR:
// For Offsetof(s.f), s may itself be a pointer,
// but accessing f must not otherwise involve
// indirection via embedded pointer types.
if r.Left() != sbase {
base.Errorf("invalid expression %v: selector implies indirection of embedded %v", n, r.Left())
return 0
}
fallthrough
case ir.ODOT:
v += r.Offset()
default:
ir.Dump("unsafenmagic", n.Left())
base.Fatalf("impossible %#v node after dot insertion", r.Op())
}
}
return v
}
base.Fatalf("unexpected op %v", n.Op())
return 0
}
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