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https://github.com/golang/go
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a069cf048d
Before, an unnamed return value turned into an ONAME node n with n->sym named ~anon%d, and n->orig == n. A blank-named return value turned into an ONAME node n with n->sym named ~anon%d but n->orig == the original blank n. Code generation and printing uses n->orig, so that this node formatted as _. But some code does not use n->orig. In particular the liveness code does not know about the n->orig convention and so mishandles blank identifiers. It is possible to fix but seemed better to avoid the confusion entirely. Now the first kind of node is named ~r%d and the second ~b%d; both have n->orig == n, so that it doesn't matter whether code uses n or n->orig. After this change the ->orig field is only used for other kinds of expressions, not for ONAME nodes. This requires distinguishing ~b from ~r names in a few places that care. It fixes a liveness analysis bug without actually changing the liveness code. TBR=ken2 CC=golang-codereviews https://golang.org/cl/63630043
89 lines
1.8 KiB
Go
89 lines
1.8 KiB
Go
// errorcheck -0 -l -live
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// Copyright 2014 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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func f1() {
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var x *int
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print(&x) // ERROR "live at call to printpointer: x$"
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print(&x) // ERROR "live at call to printpointer: x$"
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}
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func f2(b bool) {
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if b {
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print(0) // nothing live here
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return
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}
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var x *int
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print(&x) // ERROR "live at call to printpointer: x$"
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print(&x) // ERROR "live at call to printpointer: x$"
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}
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func f3(b bool) {
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print(0)
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if b == false {
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print(0) // nothing live here
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return
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}
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if b {
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var x *int
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print(&x) // ERROR "live at call to printpointer: x$"
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print(&x) // ERROR "live at call to printpointer: x$"
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} else {
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var y *int
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print(&y) // ERROR "live at call to printpointer: y$"
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print(&y) // ERROR "live at call to printpointer: y$"
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}
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print(0) // ERROR "live at call to printint: x y$"
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}
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// The old algorithm treated x as live on all code that
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// could flow to a return statement, so it included the
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// function entry and code above the declaration of x
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// but would not include an indirect use of x in an infinite loop.
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// Check that these cases are handled correctly.
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func f4(b1, b2 bool) { // x not live here
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if b2 {
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print(0) // x not live here
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return
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}
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var z **int
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x := new(int)
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*x = 42
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z = &x
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print(**z) // ERROR "live at call to printint: x z$"
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if b2 {
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print(1) // ERROR "live at call to printint: x$"
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return
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}
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for {
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print(**z) // ERROR "live at call to printint: x z$"
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}
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}
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func f5(b1 bool) {
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var z **int
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if b1 {
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x := new(int)
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*x = 42
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z = &x
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} else {
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y := new(int)
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*y = 54
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z = &y
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}
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print(**z) // ERROR "live at call to printint: x y$"
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}
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// confusion about the _ result used to cause spurious "live at entry to f6: _".
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func f6() (_, y string) {
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y = "hello"
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return
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}
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