mirror of
https://github.com/golang/go
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c33d45a898
During package initialization, the compiler tries to optimize:
var A = "foo"
var B = A
into
var A = "foo"
var B = "foo"
so that we can statically initialize both A and B and skip emitting
dynamic initialization code to assign "B = A".
However, this isn't safe in the presence of cmd/link's -X flag, which
might overwrite an initialized string-typed variable at link time. In
particular, if cmd/link changes A's static initialization, it won't
know it also needs to change B's static initialization.
To address this, this CL disables this optimization for string-typed
variables.
Fixes #34675.
Change-Id: I1c18f3b855f6d7114aeb39f96aaaf1b452b88236
Reviewed-on: https://go-review.googlesource.com/c/go/+/198657
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
71 lines
1.6 KiB
Go
71 lines
1.6 KiB
Go
// +build !nacl,!js
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// run
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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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// Run the linkx test.
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package main
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import (
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"bytes"
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"fmt"
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"os"
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"os/exec"
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"strings"
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)
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func main() {
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// test(" ") // old deprecated & removed syntax
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test("=") // new syntax
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}
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func test(sep string) {
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// Successful run
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cmd := exec.Command("go", "run", "-ldflags=-X main.tbd"+sep+"hello -X main.overwrite"+sep+"trumped -X main.nosuchsymbol"+sep+"neverseen", "linkx.go")
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var out, errbuf bytes.Buffer
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cmd.Stdout = &out
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cmd.Stderr = &errbuf
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err := cmd.Run()
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if err != nil {
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fmt.Println(errbuf.String())
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fmt.Println(out.String())
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fmt.Println(err)
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os.Exit(1)
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}
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want := "hello\nhello\nhello\ntrumped\ntrumped\ntrumped\n"
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got := out.String()
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if got != want {
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fmt.Printf("got %q want %q\n", got, want)
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os.Exit(1)
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}
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// Issue 8810
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cmd = exec.Command("go", "run", "-ldflags=-X main.tbd", "linkx.go")
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_, err = cmd.CombinedOutput()
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if err == nil {
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fmt.Println("-X linker flag should not accept keys without values")
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os.Exit(1)
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}
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// Issue 9621
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cmd = exec.Command("go", "run", "-ldflags=-X main.b=false -X main.x=42", "linkx.go")
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outx, err := cmd.CombinedOutput()
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if err == nil {
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fmt.Println("-X linker flag should not overwrite non-strings")
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os.Exit(1)
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}
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outstr := string(outx)
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if !strings.Contains(outstr, "main.b") {
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fmt.Printf("-X linker flag did not diagnose overwrite of main.b:\n%s\n", outstr)
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os.Exit(1)
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}
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if !strings.Contains(outstr, "main.x") {
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fmt.Printf("-X linker flag did not diagnose overwrite of main.x:\n%s\n", outstr)
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os.Exit(1)
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}
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}
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