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3f2cb493e5
Reuse the same mechanisms for handling universal builtins like len to handle unsafe.Sizeof, etc. Allows us to drop package unsafe's export data, and simplifies some code. Updates #17508. Change-Id: I620e0617c24e57e8a2d7cccd0e2de34608779656 Reviewed-on: https://go-review.googlesource.com/31433 Run-TryBot: Matthew Dempsky <mdempsky@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Robert Griesemer <gri@golang.org>
74 lines
1.8 KiB
Go
74 lines
1.8 KiB
Go
// Copyright 2009 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 gc
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// evalunsafe evaluates a package unsafe operation and returns the result.
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func evalunsafe(n *Node) int64 {
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switch n.Op {
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case OALIGNOF, OSIZEOF:
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n.Left = typecheck(n.Left, Erv)
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n.Left = defaultlit(n.Left, nil)
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tr := n.Left.Type
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if tr == nil {
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yyerror("invalid expression %v", n)
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return 0
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}
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dowidth(tr)
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if n.Op == OALIGNOF {
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return int64(tr.Align)
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}
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return tr.Width
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case OOFFSETOF:
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// must be a selector.
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if n.Left.Op != OXDOT {
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yyerror("invalid expression %v", n)
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return 0
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}
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// Remember base of selector to find it back after dot insertion.
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// Since r->left may be mutated by typechecking, check it explicitly
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// first to track it correctly.
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n.Left.Left = typecheck(n.Left.Left, Erv)
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base := n.Left.Left
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n.Left = typecheck(n.Left, Erv)
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switch n.Left.Op {
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case ODOT, ODOTPTR:
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break
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case OCALLPART:
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yyerror("invalid expression %v: argument is a method value", n)
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return 0
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default:
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yyerror("invalid expression %v", n)
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return 0
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}
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// Sum offsets for dots until we reach base.
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var v int64
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for r := n.Left; r != base; r = r.Left {
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switch r.Op {
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case ODOTPTR:
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// For Offsetof(s.f), s may itself be a pointer,
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// but accessing f must not otherwise involve
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// indirection via embedded pointer types.
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if r.Left != base {
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yyerror("invalid expression %v: selector implies indirection of embedded %v", n, r.Left)
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return 0
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}
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fallthrough
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case ODOT:
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v += r.Xoffset
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default:
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Dump("unsafenmagic", n.Left)
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Fatalf("impossible %#v node after dot insertion", r.Op)
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}
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}
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return v
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}
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Fatalf("unexpected op %v", n.Op)
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return 0
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}
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