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cmd/compile: cannot export DCLTYPE (50) node #48328

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Merovius opened this issue Sep 10, 2021 · 1 comment
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cmd/compile: cannot export DCLTYPE (50) node #48328

Merovius opened this issue Sep 10, 2021 · 1 comment

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@Merovius
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@Merovius Merovius commented Sep 10, 2021

What version of Go are you using (go version)?

$ gotip version                                                                                                       1
go version devel go1.18-cf2fe5d Fri Sep 10 17:15:37 2021 +0000 linux/amd64

Does this issue reproduce with the latest release?

With gotip yes, with the latest release not. It's a generics issue.

What operating system and processor architecture are you using (go env)?

go env Output
$ gotip env
GO111MODULE="on"
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/mero/.cache/go-build"
GOENV="/home/mero/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/mero/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/mero"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/home/mero/sdk/gotip"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/home/mero/sdk/gotip/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="devel go1.18-cf2fe5d Fri Sep 10 17:15:37 2021 +0000"
GCCGO="/usr/bin/gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/mero/tmp/x/go.mod"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build1538326350=/tmp/go-build -gno-record-gcc-switches"

What did you do?

Trying to build this program using gotip (please ignore that it's a bad idea or broken code, just playing around):

package main

import (
	"fmt"
	"reflect"
	"sync"
	"unsafe"
)

func main() {
	h := Hasher[int]()
	fmt.Printf("%.16x\n", h(42, 0))
}

func Hasher[T comparable]() func(T, uintptr) uintptr {
	rt := reflect.TypeOf(*new(T))
	if h, ok := cache.Load(rt); ok {
		return h.(func(T, uintptr) uintptr)
	}
	mt := reflect.MapOf(rt, reflect.TypeOf(struct{}{}))
	ptr_size := reflect.TypeOf(mt).Size()
	rtype_size := reflect.TypeOf(mt).Elem().Size()

	rtype_base := (*[2]unsafe.Pointer)(unsafe.Pointer(&mt))[1]
	hasher_ptr := unsafe.Add(rtype_base, rtype_size+3*ptr_size)

	type hasherFn func(unsafe.Pointer, uintptr) uintptr
	hasher := *(*hasherFn)(unsafe.Pointer(&hasher_ptr))

	h := func(v T, seed uintptr) uintptr {
		return hasher(unsafe.Pointer(&v), seed)
	}
	cache.LoadOrStore(rt, h)
	return h
}

var cache sync.Map

What did you expect to see?

Nothing

What did you see instead?

Compiler error:

./x.go:34:2: internal compiler error: cannot export DCLTYPE (50) node
==> please file an issue and assign to gri@

Stack trace
goroutine 1 [running]:
runtime/debug.Stack()
	/home/mero/sdk/gotip/src/runtime/debug/stack.go:24 +0x65
cmd/compile/internal/base.FatalfAt({0xc0c0, 0xc0}, {0xd1a707, 0x47}, {0xc0000fd690, 0x2, 0x2})
	/home/mero/sdk/gotip/src/cmd/compile/internal/base/print.go:227 +0x154
cmd/compile/internal/base.Fatalf(...)
	/home/mero/sdk/gotip/src/cmd/compile/internal/base/print.go:196
cmd/compile/internal/typecheck.(*exportWriter).expr(0xc0006b6620, {0xe6b8d8, 0xc00000c0c0})
	/home/mero/sdk/gotip/src/cmd/compile/internal/typecheck/iexport.go:2072 +0x19dd
cmd/compile/internal/typecheck.(*exportWriter).node(0xc0006b1ec0, {0xe6b8d8, 0xc00000c0c0})
	/home/mero/sdk/gotip/src/cmd/compile/internal/typecheck/iexport.go:1455 +0x7b
cmd/compile/internal/typecheck.(*exportWriter).stmtList(0xc0006b6620, {0xc0000ae600, 0xc, 0xc0006b1ec0})
	/home/mero/sdk/gotip/src/cmd/compile/internal/typecheck/iexport.go:1446 +0x76
cmd/compile/internal/typecheck.(*exportWriter).funcBody(0xc0006b6620, 0xc00009e580)
	/home/mero/sdk/gotip/src/cmd/compile/internal/typecheck/iexport.go:1441 +0x5b
cmd/compile/internal/typecheck.(*iexporter).doInline(0xc0000f0bb0, 0xc0000e9860)
	/home/mero/sdk/gotip/src/cmd/compile/internal/typecheck/iexport.go:632 +0xc5
cmd/compile/internal/typecheck.(*exportWriter).funcExt(0xc0006b64d0, 0xc0000e9860)
	/home/mero/sdk/gotip/src/cmd/compile/internal/typecheck/iexport.go:1378 +0x1b6
cmd/compile/internal/typecheck.(*iexporter).doDecl(0xc0000f0bb0, 0xc0000e9860)
	/home/mero/sdk/gotip/src/cmd/compile/internal/typecheck/iexport.go:503 +0x21e
cmd/compile/internal/typecheck.WriteExports({0xe52660, 0xc0006b1d10}, 0x1)
	/home/mero/sdk/gotip/src/cmd/compile/internal/typecheck/iexport.go:301 +0x2e5
cmd/compile/internal/noder.WriteExports(0xc0006676f0)
	/home/mero/sdk/gotip/src/cmd/compile/internal/noder/export.go:40 +0x7a
cmd/compile/internal/gc.dumpCompilerObj(0xc0006676f0)
	/home/mero/sdk/gotip/src/cmd/compile/internal/gc/obj.go:107 +0x28
cmd/compile/internal/gc.dumpobj1({0x7ffe4c471c76, 0x24}, 0x3)
	/home/mero/sdk/gotip/src/cmd/compile/internal/gc/obj.go:63 +0x17b
cmd/compile/internal/gc.dumpobj()
	/home/mero/sdk/gotip/src/cmd/compile/internal/gc/obj.go:44 +0x36
cmd/compile/internal/gc.Main(0xd21e78)
	/home/mero/sdk/gotip/src/cmd/compile/internal/gc/main.go:329 +0x10ef
main.main()
	/home/mero/sdk/gotip/src/cmd/compile/main.go:55 +0xdd

I don't think I can assign anyone, but let me try summoning @griesemer :)

@randall77
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@randall77 randall77 commented Sep 10, 2021

Closing as a dup of #47631

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@randall77 randall77 closed this Sep 10, 2021
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