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cmd/compile: println(^uint(0)) fails to compile #21887

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mmacdermaid opened this issue Sep 14, 2017 · 6 comments
Closed

cmd/compile: println(^uint(0)) fails to compile #21887

mmacdermaid opened this issue Sep 14, 2017 · 6 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
Milestone
Go1.10

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@mmacdermaid
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What did you do?

https://play.golang.org/p/bIg5Wj5I4Q

In local builds

println(^uint(0))

Is a compile error

constant 18446744073709551615 overflows int64

In local tests and builds it prints -1

func TestOverflow(t *testing.T) {
	asd := ^uint(0)
	println(asd)
}

go test -test.run TestOverflow
-1

What did you expect to see?

4294967295

What did you see instead?

-1

System details

go version go1.9 linux/amd64
GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/mmacdermaid/git/go"
GORACE=""
GOROOT="/home/mmacdermaid/goinstall/go"
GOTOOLDIR="/home/mmacdermaid/goinstall/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build297215887=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOROOT/bin/go version: go version go1.9 linux/amd64
GOROOT/bin/go tool compile -V: compile version go1.9
uname -sr: Linux 4.4.0-57-generic
Distributor ID:	Ubuntu
Description:	Ubuntu 16.04.2 LTS
Release:	16.04
Codename:	xenial
/lib/x86_64-linux-gnu/libc.so.6: GNU C Library (Ubuntu GLIBC 2.23-0ubuntu9) stable release version 2.23, by Roland McGrath et al.
gdb --version: GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.5) 7.11.1
@ianlancetaylor ianlancetaylor changed the title ^uint(0) not yielding correct results cmd/compile: println(^uint(0)) fails to compile Sep 14, 2017
@ianlancetaylor ianlancetaylor added this to the Go1.10 milestone Sep 14, 2017
@ianlancetaylor
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I think the problem is specific to println(^uint(0)). This fails:

package main

func main() {
	println(^uint(0))
}

Replacing println with fmt.Println works fine.

@ianlancetaylor ianlancetaylor added the NeedsFix The path to resolution is known, but the work has not been done. label Sep 14, 2017
@davecheney
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davecheney commented Sep 14, 2017 via email

@mmacdermaid
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👍 Good to know it's just println(). I can confirm using fmt.Println() over here correctly prints the right results.

@davecheney
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I'm going to close this as there doesn't seem to be an issue. println isn't really part of the language spec, it's just a vestigial part of the bootstrapping process.

https://golang.org/ref/spec#Bootstrapping

@gopherbot
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Change https://golang.org/cl/63971 mentions this issue: cmd/compile: fix print/println when input is uint

@odeke-em
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Reopening this as there is a proper/code fix that @anfernee has up for review.

@odeke-em odeke-em reopened this Sep 17, 2017
@golang golang locked and limited conversation to collaborators Sep 26, 2018
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done.
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Go1.10
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@davecheney @mmacdermaid @ianlancetaylor @odeke-em @gopherbot