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cmd/compile: add Type.WidthCalculated
Prior to this CL, Type.Width != 0 was the mark of a Type whose Width had been calculated. As a result, dowidth always recalculated the width of struct{}. This, combined with the prohibition on calculating the width of a FuncArgsStruct and the use of struct{} as a function argument, meant that there were circumstances in which it was forbidden to call dowidth on a type. This inhibits refactoring to call dowidth automatically, rather than explicitly. Instead add a helper method, Type.WidthCalculated, and implement as Type.Align > 0. Type.Width is not a good candidate for tracking whether the width has been calculated; 0 is a value type width, and Width is subject to too much magic value game-playing. For good measure, add a test for #11354. Change-Id: Ie9a9fb5d924e7a2010c1904ae5e38ed4a38eaeb2 Reviewed-on: https://go-review.googlesource.com/38468 Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com>
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@ -159,14 +159,6 @@ func dowidth(t *Type) {
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return
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}
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if t.Width > 0 {
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if t.Align == 0 {
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// See issue 11354
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Fatalf("zero alignment with nonzero size %v", t)
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}
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return
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}
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if t.Width == -2 {
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if !t.Broke() {
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t.SetBroke(true)
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@ -177,6 +169,10 @@ func dowidth(t *Type) {
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return
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}
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if t.WidthCalculated() {
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return
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}
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// break infinite recursion if the broken recursive type
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// is referenced again
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if t.Broke() && t.Width == 0 {
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@ -266,7 +262,7 @@ func dowidth(t *Type) {
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if t1.Elem().Width >= 1<<16 {
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yyerror("channel element type too large (>64kB)")
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}
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t.Width = 1
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w = 1 // anything will do
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case TMAP: // implemented as pointer
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w = int64(Widthptr)
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@ -353,7 +349,7 @@ func dowidth(t *Type) {
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t.Width = w
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if t.Align == 0 {
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if w > 8 || w&(w-1) != 0 {
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if w > 8 || w&(w-1) != 0 || w == 0 {
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Fatalf("invalid alignment for %v", t)
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}
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t.Align = uint8(w)
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@ -891,6 +891,10 @@ func (t *Type) isDDDArray() bool {
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return t.Extra.(*ArrayType).Bound < 0
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}
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func (t *Type) WidthCalculated() bool {
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return t.Align > 0
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}
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// ArgWidth returns the total aligned argument size for a function.
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// It includes the receiver, parameters, and results.
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func (t *Type) ArgWidth() int64 {
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15
test/fixedbugs/issue11354.go
Normal file
15
test/fixedbugs/issue11354.go
Normal file
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@ -0,0 +1,15 @@
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// compile
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// Copyright 2017 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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type X int
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var foo = map[int]X{}
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var bar = map[int][8]X{}
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func main() {}
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