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fix: data race in ehash due to unsynchronized lazy init of Map.typ #4

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Merged
lrita merged 1 commit into from
Apr 16, 2026
Merged

fix: data race in ehash due to unsynchronized lazy init of Map.typ #4

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2 changes: 1 addition & 1 deletion go.mod
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Original file line number Diff line number Diff line change
@@ -1,3 +1,3 @@
module github.com/lrita/cmap

go 1.18
go 1.19
28 changes: 14 additions & 14 deletions map.go
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Original file line number Diff line number Diff line change
Expand Up @@ -16,7 +16,7 @@ import (
type Map[K comparable, V any] struct {
lock sync.Mutex
inode unsafe.Pointer // *inode2
typ *rtype
typ atomic.Pointer[rtype]

@lrita lrita Mar 29, 2026

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Could you use unsafe.Pointer here, or upgrade the minimum dependency in go.mod to a version that supports this type?

@stuchl4n3k stuchl4n3k Apr 14, 2026

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Fixed, thanks.

count int64
}

Expand Down Expand Up @@ -400,23 +400,23 @@ func efaceOf(ep *any) *eface {
}

func (m *Map[K, V]) ehash(i K) uintptr {
if m.typ == nil {
func() {
m.lock.Lock()
defer m.lock.Unlock()
if m.typ == nil {
// if K is interface type, then the direct reflect.TypeOf(K).Kind return reflect.Ptr
if typ := reflect.TypeOf(&i); typ.Elem().Kind() == reflect.Interface {
panic("not support interface type")
}
var e any = i
m.typ = efaceOf(&e).typ
typ := m.typ.Load()
if typ == nil {
m.lock.Lock()
if m.typ.Load() == nil {
// if K is interface type, then the direct reflect.TypeOf(K).Kind return reflect.Ptr
if typ := reflect.TypeOf(&i); typ.Elem().Kind() == reflect.Interface {
panic("not support interface type")
}
}()
var e any = i
m.typ.Store(efaceOf(&e).typ)
}
m.lock.Unlock()
typ = m.typ.Load()
}

var f eface
f.typ = m.typ
f.typ = typ
if f.typ.IsDirectIface() {
f.data = *(*unsafe.Pointer)(unsafe.Pointer(&i))
} else {
Expand Down
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