Go bench test never ends

[rodoufu]

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

$ go version
go version go1.16.2 darwin/amd64

Does this issue reproduce with the latest release?

Yes

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

go env Output

$ go env
GO111MODULE="on"
GOARCH="amd64"
GOBIN=""
GOCACHE="~/Library/Caches/go-build"
GOENV="~/Library/Application Support/go/env"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOINSECURE=""
GOMODCACHE="~/go/pkg/mod"
GOOS="darwin"
GOPATH="~/go"
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/local/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GOVCS=""
GOVERSION="go1.16.2"
GCCGO="gccgo"
AR="ar"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
GOMOD="~/git/positions/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 -arch x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/xg/xyn22y996bx5h7mbjhq1w0jm0000gn/T/go-build2191936031=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

Create this bench test

import (
	"fmt"
	"github.com/pkg/errors"
)

func BenchmarkWrap(b *testing.B) {
	b.ReportAllocs()
	err := fmt.Errorf("simple error")
	for n := 0; n < b.N; n++ {
		err = errors.Wrap(err, "open failed")
	}
}

func BenchmarkNoWrap(b *testing.B) {
	b.ReportAllocs()
	err := fmt.Errorf("simple error")
	for n := 0; n < b.N; n++ {
		err = fmt.Errorf("open failed %w", err)
	}
}

func BenchmarkWrapf(b *testing.B) {
	b.ReportAllocs()
	err := fmt.Errorf("simple error")
	for n := 0; n < b.N; n++ {
		err = errors.Wrapf(err, "open failed: %v", err)
	}
}

Then try to run it like:

$ go test -bench=. -run=Bench ./...

What did you expect to see?

I would expect to see the execution time for all tests.

What did you see instead?

It is getting stuck with the BenchmarkWrapf.

$ go test -bench=. -run=Bench ./...
goos: darwin
goarch: amd64
cpu: Intel(R) Core(TM) i5-1038NG7 CPU @ 2.00GHz
BenchmarkWrap-8          1408294               756.3 ns/op           336 B/op          4 allocs/op
BenchmarkNoWrap-8          38275            341847 ns/op          462277 B/op          4 allocs/op
BenchmarkWrapf-8        ^Csignal: interrupt
FAIL    pkg/domain        443.597s

[ianlancetaylor]

Each time through the loop the error message gets longer. The long error message can't be garbage collected, so your program will eventually start swapping. It's not hanging, it's just taking a very very long time to complete.

Try this instead:

func BenchmarkWrap(b *testing.B) {
	b.ReportAllocs()
	err := fmt.Errorf("simple error")
	for n := 0; n < b.N; n++ {
		_ = errors.Wrap(err, "open failed")
	}
}

func BenchmarkNoWrap(b *testing.B) {
	b.ReportAllocs()
	err := fmt.Errorf("simple error")
	for n := 0; n < b.N; n++ {
		_ = fmt.Errorf("open failed %w", err)
	}
}

func BenchmarkWrapf(b *testing.B) {
	b.ReportAllocs()
	err := fmt.Errorf("simple error")
	for n := 0; n < b.N; n++ {
		_ = errors.Wrapf(err, "open failed: %v", err)
	}
}