cmd/compile: go1.8rc1 failure when comparing interface with struct #18661

danw · 2017-01-15T00:43:06Z

What did you do?

package main

func test(obj interface{}) {
        if obj != struct{a *string}{} {
        }
}

func main() {}

What did you expect to see?

Successful compile:

$ go build test.go
$

What did you see instead?

$ go build test.go
# test
./test.go:4: internal compiler error: arguments of comparison must be lvalues - <node IDATA> statictmp_0

goroutine 1 [running]:
runtime/debug.Stack(0x0, 0x0, 0x0)
	/usr/local/go/src/runtime/debug/stack.go:24 +0x79
cmd/compile/internal/gc.Fatalf(0x16c0b76, 0x2f, 0xc42034fd90, 0x2, 0x2)
	/usr/local/go/src/cmd/compile/internal/gc/subr.go:167 +0x226
cmd/compile/internal/gc.walkcompare(0xc420352090, 0xc420350860, 0xc42033fc20)
	/usr/local/go/src/cmd/compile/internal/gc/walk.go:3121 +0x1b7
cmd/compile/internal/gc.walkexpr(0xc420352090, 0xc420350860, 0xc42033fef0)
	/usr/local/go/src/cmd/compile/internal/gc/walk.go:580 +0x7d91
cmd/compile/internal/gc.walkexpr(0xc420352120, 0xc42033f330, 0xc420352120)
	/usr/local/go/src/cmd/compile/internal/gc/walk.go:591 +0x2038
cmd/compile/internal/gc.finishcompare(0xc42033f3b0, 0xc420352120, 0xc42033f330, 0xc420352120)
	/usr/local/go/src/cmd/compile/internal/gc/walk.go:3202 +0x50
cmd/compile/internal/gc.walkcompare(0xc42033f3b0, 0xc42033f330, 0xc42033fc20)
	/usr/local/go/src/cmd/compile/internal/gc/walk.go:3092 +0xbe9
cmd/compile/internal/gc.walkexpr(0xc42033f3b0, 0xc42033f330, 0x0)
	/usr/local/go/src/cmd/compile/internal/gc/walk.go:580 +0x7d91
cmd/compile/internal/gc.walkstmt(0xc42033f320, 0xc42032c7a0)
	/usr/local/go/src/cmd/compile/internal/gc/walk.go:280 +0x1326
cmd/compile/internal/gc.walkstmtlist(0xc42000c5e8, 0x1, 0x1)
	/usr/local/go/src/cmd/compile/internal/gc/walk.go:80 +0x44
cmd/compile/internal/gc.walk(0xc42033ec60)
	/usr/local/go/src/cmd/compile/internal/gc/walk.go:65 +0x1c0
cmd/compile/internal/gc.compile(0xc42033ec60)
	/usr/local/go/src/cmd/compile/internal/gc/pgen.go:350 +0x1c5
cmd/compile/internal/gc.funccompile(0xc42033ec60)
	/usr/local/go/src/cmd/compile/internal/gc/dcl.go:1292 +0xdc
cmd/compile/internal/gc.Main()
	/usr/local/go/src/cmd/compile/internal/gc/main.go:463 +0x1f0d
main.main()
	/usr/local/go/src/cmd/compile/main.go:50 +0xfe

$

Does this issue reproduce with the latest release (go1.7.4)?

This happens on go1.8rc1, but not go1.7.4.

The above test case was simplified from code on android.googlesource.com which broke when we upgraded to go1.8rc1.

System details

go version go1.8rc1 darwin/amd64
GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/dwillemsen/go"
GORACE=""
GOROOT="/usr/local/go"
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/1z/kwdn8sm90vq5k6dn_lw_hxl4003qx4/T/go-build876510221=/tmp/go-build -gno-record-gcc-switches -fno-common"
CXX="clang++"
CGO_ENABLED="1"
PKG_CONFIG="pkg-config"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
GOROOT/bin/go version: go version go1.8rc1 darwin/amd64
GOROOT/bin/go tool compile -V: compile version go1.8rc1 X:framepointer
uname -v: Darwin Kernel Version 16.3.0: Thu Nov 17 20:23:58 PST 2016; root:xnu-3789.31.2~1/RELEASE_X86_64
ProductName:	Mac OS X
ProductVersion:	10.12.2
BuildVersion:	16C67
lldb --version: lldb-360.1.70

The text was updated successfully, but these errors were encountered:

davecheney · 2017-01-15T00:59:19Z

Technically this is an assignment, not a comparison. But good catch.

…

On Sun, Jan 15, 2017 at 11:43 AM, Dan Willemsen ***@***.***> wrote: What did you do? package main func test(obj interface{}) { if obj != struct{a *string}{} { } } func main() {} What did you expect to see? Successful compile: $ go build test.go $ What did you see instead? $ go build test.go # test ./test.go:4: internal compiler error: arguments of comparison must be lvalues - <node IDATA> statictmp_0 goroutine 1 [running]: runtime/debug.Stack(0x0, 0x0, 0x0) /usr/local/go/src/runtime/debug/stack.go:24 +0x79 cmd/compile/internal/gc.Fatalf(0x16c0b76, 0x2f, 0xc42034fd90, 0x2, 0x2) /usr/local/go/src/cmd/compile/internal/gc/subr.go:167 +0x226 cmd/compile/internal/gc.walkcompare(0xc420352090, 0xc420350860, 0xc42033fc20) /usr/local/go/src/cmd/compile/internal/gc/walk.go:3121 +0x1b7 cmd/compile/internal/gc.walkexpr(0xc420352090, 0xc420350860, 0xc42033fef0) /usr/local/go/src/cmd/compile/internal/gc/walk.go:580 +0x7d91 cmd/compile/internal/gc.walkexpr(0xc420352120, 0xc42033f330, 0xc420352120) /usr/local/go/src/cmd/compile/internal/gc/walk.go:591 +0x2038 cmd/compile/internal/gc.finishcompare(0xc42033f3b0, 0xc420352120, 0xc42033f330, 0xc420352120) /usr/local/go/src/cmd/compile/internal/gc/walk.go:3202 +0x50 cmd/compile/internal/gc.walkcompare(0xc42033f3b0, 0xc42033f330, 0xc42033fc20) /usr/local/go/src/cmd/compile/internal/gc/walk.go:3092 +0xbe9 cmd/compile/internal/gc.walkexpr(0xc42033f3b0, 0xc42033f330, 0x0) /usr/local/go/src/cmd/compile/internal/gc/walk.go:580 +0x7d91 cmd/compile/internal/gc.walkstmt(0xc42033f320, 0xc42032c7a0) /usr/local/go/src/cmd/compile/internal/gc/walk.go:280 +0x1326 cmd/compile/internal/gc.walkstmtlist(0xc42000c5e8, 0x1, 0x1) /usr/local/go/src/cmd/compile/internal/gc/walk.go:80 +0x44 cmd/compile/internal/gc.walk(0xc42033ec60) /usr/local/go/src/cmd/compile/internal/gc/walk.go:65 +0x1c0 cmd/compile/internal/gc.compile(0xc42033ec60) /usr/local/go/src/cmd/compile/internal/gc/pgen.go:350 +0x1c5 cmd/compile/internal/gc.funccompile(0xc42033ec60) /usr/local/go/src/cmd/compile/internal/gc/dcl.go:1292 +0xdc cmd/compile/internal/gc.Main() /usr/local/go/src/cmd/compile/internal/gc/main.go:463 +0x1f0d main.main() /usr/local/go/src/cmd/compile/main.go:50 +0xfe $ Does this issue reproduce with the latest release (go1.7.4)? This happens on go1.8rc1, but not go1.7.4. The above test case was simplified from code on android.googlesource.com which broke when we upgraded to go1.8rc1. System details go version go1.8rc1 darwin/amd64 GOARCH="amd64" GOBIN="" GOEXE="" GOHOSTARCH="amd64" GOHOSTOS="darwin" GOOS="darwin" GOPATH="/Users/dwillemsen/go" GORACE="" GOROOT="/usr/local/go" GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64" GCCGO="gccgo" CC="clang" GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/1z/kwdn8sm90vq5k6dn_lw_hxl4003qx4/T/go-build876510221=/tmp/go-build -gno-record-gcc-switches -fno-common" CXX="clang++" CGO_ENABLED="1" PKG_CONFIG="pkg-config" CGO_CFLAGS="-g -O2" CGO_CPPFLAGS="" CGO_CXXFLAGS="-g -O2" CGO_FFLAGS="-g -O2" CGO_LDFLAGS="-g -O2" GOROOT/bin/go version: go version go1.8rc1 darwin/amd64 GOROOT/bin/go tool compile -V: compile version go1.8rc1 X:framepointer uname -v: Darwin Kernel Version 16.3.0: Thu Nov 17 20:23:58 PST 2016; root:xnu-3789.31.2~1/RELEASE_X86_64 ProductName: Mac OS X ProductVersion: 10.12.2 BuildVersion: 16C67 lldb --version: lldb-360.1.70 — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#18661>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAAcA1k-fg12zstWjGaY6IrrgmTw5qICks5rSWucgaJpZM4LjyZ-> .

bradfitz · 2017-01-15T01:28:14Z

Thanks for the report and reduction.

JayNakrani · 2017-01-15T02:21:00Z

Below is Dump() of cmpl and cmpr at walk.go#L3120. Difference is that, we now generate OIDATA node for cmpl.

At tip:

cmpl [0xc42036a000]
.   IDATA u(2) l(4) tc(1) STRUCT-struct { a *string }
.   .   NAME-p.obj u(1) a(true) g(1) l(3) x(0) class(PPARAM) f(1) esc(no) tc(1) used(true) INTER-interface {}
cmpr [0xc420351c20]
.   NAME-p.statictmp_0 u(1) a(true) l(4) x(0) class(PEXTERN) f(1) tc(1) used(true) STRUCT-struct { a *string }
issue18661.go:4: internal compiler error: arguments of comparison must be lvalues - <node IDATA> statictmp_0

In branch release-branch.go1.7:

cmpl [0xc420429200]
.   NAME-p.autotmp_1 u(1) a(true) l(4) x(0+0) class(PAUTO) esc(N) tc(1) addrtaken assigned used(true) STRUCT-struct { a *string }
cmpr [0xc420429170]
.   NAME-p.statictmp_0 u(1) a(true) l(4) x(0+0) class(PEXTERN) f(1) tc(1) used(true) STRUCT-struct { a *string }

OIDATA was added in golang.org/cl/26659. Perhaps, islvalue() just needs to handle that case, now that compiler generates it. @josharian to confirm.

davecheney · 2017-01-15T02:22:25Z

I don't think this is correct, the code sample provided by the OP was a syntax error, it should have been spotted earlier before it got to this part of the code gen.

…

On Sun, 15 Jan 2017, 13:21 Dhananjay Nakrani ***@***.***> wrote: Below is Dump() of cmpl and cmpr at walk.go#L3120 <https://github.com/golang/go/blob/75d367e34b42b8428d535122eadead87a0c11c8c/src/cmd/compile/internal/gc/walk.go#L3120>. Difference is that, we now generate OIDATA node for cmpl. At tip: cmpl [0xc42036a000] . IDATA u(2) l(4) tc(1) STRUCT-struct { a *string } . . NAME-p.obj u(1) a(true) g(1) l(3) x(0) class(PPARAM) f(1) esc(no) tc(1) used(true) INTER-interface {} cmpr [0xc420351c20] . NAME-p.statictmp_0 u(1) a(true) l(4) x(0) class(PEXTERN) f(1) tc(1) used(true) STRUCT-struct { a *string } issue18661.go:4: internal compiler error: arguments of comparison must be lvalues - <node IDATA> statictmp_0 In branch release-branch.go1.7: cmpl [0xc420429200] . NAME-p.autotmp_1 u(1) a(true) l(4) x(0+0) class(PAUTO) esc(N) tc(1) addrtaken assigned used(true) STRUCT-struct { a *string } cmpr [0xc420429170] . NAME-p.statictmp_0 u(1) a(true) l(4) x(0+0) class(PEXTERN) f(1) tc(1) used(true) STRUCT-struct { a *string } OIDATA was added in golang.org/cl/26659 <https://go-review.googlesource.com/#/c/26659/3/src/cmd/compile/internal/gc/syntax.go>. Perhaps, lvalue() just needs to handle that case, now that compiler generates it. @josharian <https://github.com/josharian> to confirm. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#18661 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAAcA6ZUY_LH5wvTa7fy3uyN8TNcxnLFks5rSYKOgaJpZM4LjyZ-> .

dsnet · 2017-01-15T03:59:36Z

Git bisect reports 1a7fc7b as the issue.

\cc @josharian @randall77

josharian · 2017-01-15T05:41:24Z

Thanks for the report and concise reproducer, @danw. CL to come shortly.

JayNakrani · 2017-01-15T05:41:45Z

@davecheney

the code sample provided by the OP was a syntax error, it should have been spotted earlier before it got to this part of the code gen

Perhaps, I'm missing something. What's the syntax error here? The spec says,

"A value x of non-interface type X and a value t of interface type T are comparable when values of type X are comparable and X implements T. They are equal if t's dynamic type is identical to X and t's dynamic value is equal to x"

I think obj != struct{...}{} satisfies that.

gopherbot · 2017-01-15T06:00:15Z

CL https://golang.org/cl/35236 mentions this issue.

davecheney · 2017-01-15T06:28:46Z

I'm terribly sorry, I mistook != For :=. Please ignore my comments.

…

On Sun, 15 Jan 2017, 17:00 GopherBot ***@***.***> wrote: CL https://golang.org/cl/35236 mentions this issue. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#18661 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAAcA4rN-Fo2IgewoZvOsm_bmupFuaW6ks5rSbXwgaJpZM4LjyZ-> .

gopherbot · 2017-02-02T02:35:51Z

CL https://golang.org/cl/36126 mentions this issue.

Make sure that the lack of an lvalue doesn't cause extra side-effects. Updates #18661 Updates #18739 Change-Id: I52eb4b4a5c6f8ff5cddd2115455f853c18112c19 Reviewed-on: https://go-review.googlesource.com/36126 Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Matthew Dempsky <mdempsky@google.com>

bradfitz added this to the Go1.8 milestone Jan 15, 2017

bradfitz assigned mdempsky and griesemer Jan 15, 2017

bradfitz added the NeedsFix The path to resolution is known, but the work has not been done. label Jan 15, 2017

gopherbot closed this as completed in 5b708a6 Jan 16, 2017

golang locked and limited conversation to collaborators Feb 2, 2018

gopherbot added the FrozenDueToAge label Feb 2, 2018

rsc unassigned mdempsky and griesemer Jun 23, 2022

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

cmd/compile: go1.8rc1 failure when comparing interface with struct #18661

cmd/compile: go1.8rc1 failure when comparing interface with struct #18661

danw commented Jan 15, 2017

davecheney commented Jan 15, 2017 via email

bradfitz commented Jan 15, 2017

JayNakrani commented Jan 15, 2017 •

edited

davecheney commented Jan 15, 2017 via email

dsnet commented Jan 15, 2017

josharian commented Jan 15, 2017

JayNakrani commented Jan 15, 2017

gopherbot commented Jan 15, 2017

davecheney commented Jan 15, 2017 via email

gopherbot commented Feb 2, 2017

cmd/compile: go1.8rc1 failure when comparing interface with struct #18661

cmd/compile: go1.8rc1 failure when comparing interface with struct #18661

Comments

danw commented Jan 15, 2017

What did you do?

What did you expect to see?

What did you see instead?

Does this issue reproduce with the latest release (go1.7.4)?

System details

davecheney commented Jan 15, 2017 via email

bradfitz commented Jan 15, 2017

JayNakrani commented Jan 15, 2017 • edited

davecheney commented Jan 15, 2017 via email

dsnet commented Jan 15, 2017

josharian commented Jan 15, 2017

JayNakrani commented Jan 15, 2017

gopherbot commented Jan 15, 2017

davecheney commented Jan 15, 2017 via email

gopherbot commented Feb 2, 2017

JayNakrani commented Jan 15, 2017 •

edited