Closed
Description
What version of Go are you using (go version)?
$ go version go version go1.19.4 windows/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 set GO111MODULE= set GOARCH=amd64 set GOBIN= set GOCACHE=C:\Users\Stephen\AppData\Local\go-build set GOENV=C:\Users\Stephen\AppData\Roaming\go\env set GOEXE=.exe set GOEXPERIMENT= set GOFLAGS= set GOHOSTARCH=amd64 set GOHOSTOS=windows set GOINSECURE= set GOMODCACHE=C:\msys64\mingw64\pkg\mod set GONOPROXY= set GONOSUMDB= set GOOS=windows set GOPATH=C:/msys64/mingw64 set GOPRIVATE= set GOPROXY=https://proxy.golang.org,direct set GOROOT=C:\Program Files\Go set GOSUMDB=sum.golang.org set GOTMPDIR= set GOTOOLDIR=C:\Program Files\Go\pkg\tool\windows_amd64 set GOVCS= set GOVERSION=go1.19.4 set GCCGO=gccgo set GOAMD64=v1 set AR=ar set CC=gcc set CXX=g++ set CGO_ENABLED=1 set GOMOD=C:\Users\Stephen\projects\vkngwrapper\math\go.mod set GOWORK=C:\Users\Stephen\projects\vkngwrapper\go.work set CGO_CFLAGS=-g -O2 set CGO_CPPFLAGS= set CGO_CXXFLAGS=-g -O2 set CGO_FFLAGS=-g -O2 set CGO_LDFLAGS=-g -O2 set PKG_CONFIG=pkg-config set GOGCCFLAGS=-m64 -mthreads -Wl,--no-gc-sections -fmessage-length=0 -fdebug-prefix-map=C:\msys64\tmp\go-build13049274=/tmp/go-build -gno-record-gcc-switches
What did you do?
Ran the following benchmarks:
package math
import "testing"
var output int
type Object struct {
Val int
}
func (o *Object) Initialize() *Object {
o.Val = 5
return o
}
func (o *Object) Update() *Object {
o.Val = o.Val + 1
return o
}
func BenchmarkNoAllocs(b *testing.B) {
b.ReportAllocs()
for i := 0; i < b.N; i++ {
var obj Object
obj.Initialize()
obj.Update()
output = obj.Val
}
}
func BenchmarkAllocs(b *testing.B) {
b.ReportAllocs()
for i := 0; i < b.N; i++ {
var obj Object
obj.Initialize().Update()
output = obj.Val
}
}
What did you expect to see?
I expected neither benchmark to perform any allocations.
What did you see instead?
BenchmarkAllocs allocated obj onto the heap, but BenchmarkNoAllocs does not:
$ go test -test.bench=. -test.run xx .
goos: windows
goarch: amd64
pkg: github.com/vkngwrapper/math
cpu: AMD Ryzen 7 5800X 8-Core Processor
BenchmarkNoAllocs-16 1000000000 0.2160 ns/op 0 B/op 0 allocs/op
BenchmarkAllocs-16 143329258 8.381 ns/op 8 B/op 1 allocs/op
PASS
However, it does not do this in 1.18.9:
$ go1.18.9 test -test.bench=. -test.run xx .
goos: windows
goarch: amd64
pkg: github.com/vkngwrapper/math
cpu: AMD Ryzen 7 5800X 8-Core Processor
BenchmarkNoAllocs-16 1000000000 0.4301 ns/op 0 B/op 0 allocs/op
BenchmarkAllocs-16 1000000000 0.4271 ns/op 0 B/op 0 allocs/op
PASS