runtime: iterator returns map entries after clear (pre-swissmap) #70189
Description
Go version
tip
Output of go env in your module/workspace:
GO111MODULE=''
GOARCH='arm64'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/Users/khr/Library/Caches/go-build'
GOENV='/Users/khr/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMODCACHE='/Users/khr/gopath/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='darwin'
GOPATH='/Users/khr/gopath'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/Users/khr/sandbox/ro5'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/Users/khr/sandbox/ro5/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='devel go1.24-fb5dcc1526 Mon Nov 4 12:50:55 2024 -0800'
GODEBUG=''
GOTELEMETRY='local'
GOTELEMETRYDIR='/Users/khr/Library/Application Support/go/telemetry'
GCCGO='gccgo'
GOARM64='v8.0'
AR='ar'
CC='clang'
CXX='clang++'
CGO_ENABLED='1'
GOMOD='/Users/khr/sandbox/ro5/src/go.mod'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/z9/dty110711l9cr9w3ktv1_2380000gn/T/go-build1711499111=/tmp/go-build -gno-record-gcc-switches -fno-common'What did you do?
package main
func nan() float64 {
var x, y float64
return x / y
}
func main() {
m := map[float64]int{}
// Make a small map with nan keys
for i := 0; i < 8; i++ {
m[nan()] = i
}
// Start iterating on it.
start := true
for k, v := range m {
if start {
// Add some more elements.
for i := 0; i < 10; i++ {
m[float64(i)] = i
}
// Now clear the map.
clear(m)
start = false
} else {
// This should never print anything.
println(k, v)
}
}
}
When run, this should never print anything. The map is cleared during the first iteration. No map elements should survive to cause a second iteration.
There is no bug now that we've switched by default to swiss maps. The old maps, which you can get with GOEXPERIMENT=noswissmap, have this problem. This problem is present in 1.22.6 and 1.23.2. Presumably it has been there since clear was introduced in 1.21.
Seems related to #59411. Somehow the fix for that issue doesn't help here.
What did you see happen?
NaN 3
NaN 4
NaN 5
NaN 6
NaN 7
NaN 0
NaN 1
What did you expect to see?
nothing printed