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weak: don't panic when calling Value on a zero Pointer

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Currently weak.Pointer.Value will panic if the weak.Pointer is
uninitialized (zero value) which goes against it's documentation. Fix
this and add a test. While we're here, also add a test to ensure
weak.Make[T](nil) is equivalent to the zero value of weak.Pointer[T].

Fixes #71153.

Change-Id: I4d9196026360bc42a5bfcb33ce449131ec251dba
Reviewed-on: https://go-review.googlesource.com/c/go/+/641095
Reviewed-by: David Finkel <david.finkel@gmail.com>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
This commit is contained in:
Michael Anthony Knyszek 2025-01-07 16:01:46 +00:00 • committed by Gopher Robot
parent 9d0772b23e
commit d62154db83
2 changed files with 18 additions and 0 deletions
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3
src/weak/pointer.go
View file

@ -78,6 +78,9 @@ func Make[T any](ptr *T) Pointer[T] {
// If a weak pointer points to an object with a finalizer, then Value will // If a weak pointer points to an object with a finalizer, then Value will
// return nil as soon as the object's finalizer is queued for execution. // return nil as soon as the object's finalizer is queued for execution.
func (p Pointer[T]) Value() *T { func (p Pointer[T]) Value() *T {
if p.u == nil {
return nil
}
return (*T)(runtime_makeStrongFromWeak(p.u)) return (*T)(runtime_makeStrongFromWeak(p.u))
} }

15
src/weak/pointer_test.go
View file

@ -21,6 +21,15 @@ type T struct {
} }
func TestPointer(t *testing.T) { func TestPointer(t *testing.T) {
var zero weak.Pointer[T]
if zero.Value() != nil {
t.Error("Value of zero value of weak.Pointer is not nil")
}
zeroNil := weak.Make[T](nil)
if zeroNil.Value() != nil {
t.Error("Value of weak.Make[T](nil) is not nil")
}
bt := new(T) bt := new(T)
wt := weak.Make(bt) wt := weak.Make(bt)
if st := wt.Value(); st != bt { if st := wt.Value(); st != bt {
@ -41,6 +50,12 @@ func TestPointer(t *testing.T) {
} }
func TestPointerEquality(t *testing.T) { func TestPointerEquality(t *testing.T) {
var zero weak.Pointer[T]
zeroNil := weak.Make[T](nil)
if zero != zeroNil {
t.Error("weak.Make[T](nil) != zero value of weak.Pointer[T]")
}
bt := make([]*T, 10) bt := make([]*T, 10)
wt := make([]weak.Pointer[T], 10) wt := make([]weak.Pointer[T], 10)
wo := make([]weak.Pointer[int], 10) wo := make([]weak.Pointer[int], 10)