Go version
go1.23.5
Output of go env in your module/workspace:
What did you do?
I ran this benchmark:
var sinkAny any
func BenchmarkInterfaceAny(b *testing.B) {
b.ReportAllocs()
for range b.N {
sinkAny = tar.Header{}
}
}
var sinkValue reflect.Value
func BenchmarkReflectValue(b *testing.B) {
b.ReportAllocs()
for range b.N {
sinkValue = reflect.Zero(reflect.TypeFor[tar.Header]())
}
}What did you see happen?
I saw these results:
BenchmarkInterfaceAny 31895619 43.36 ns/op 224 B/op 1 allocs/op
BenchmarkReflectValue 401489182 3.021 ns/op 0 B/op 0 allocs/op
What did you expect to see?
I expected to see zero allocations in both cases.
In #33136, we optimized reflect.Zero to use a zero buffer of sufficient size to back the zero value of most types.
It seems to me that we could do the same trick for the non-reflect equivalent of storing a zero value into an interface value, where the data pointer in the interface value points to some shared zero buffer. This can be done in two ways:
- Dynamically check whether the value being stored into an interface is the zero value
- Statically detect when the value being stored into the interface value is identically equivalent to the zero value
Of course in both cases, you'll need to be careful since we're talking about a stricter definition of "zero" where the memory is equivalent to be all zeros.
Go version
go1.23.5
Output of
go envin your module/workspace:What did you do?
I ran this benchmark:
What did you see happen?
I saw these results:
What did you expect to see?
I expected to see zero allocations in both cases.
In #33136, we optimized
reflect.Zeroto use a zero buffer of sufficient size to back the zero value of most types.It seems to me that we could do the same trick for the non-reflect equivalent of storing a zero value into an interface value, where the data pointer in the interface value points to some shared zero buffer. This can be done in two ways:
Of course in both cases, you'll need to be careful since we're talking about a stricter definition of "zero" where the memory is equivalent to be all zeros.