unsafe.Offsetof() does not work properly in struct when struct is mixed of types int64 and byte #42846
Labels
Comments
tebrizetayi
changed the title
|
Structs are padded to their natural alignment. |
|
Could you make it clear,please? |
|
As davecheney pointed out this is working as intended. Struct fields in Go gc implementation are not packed as close as possible but are aligned. See also https://golang.org/ref/spec#System_considerations. e.g. 64bit atomics might require the int64 to be properly aligned and some architectures might also require this as they do aligned loads. See #36606 for a discussion of potentially allowing to specify packed struct layouts in the future. |
Sign up for free
to subscribe to this conversation on GitHub.
Already have an account?
Sign in.
What version of Go are you using (
go version)?Does this issue reproduce with the latest release?
Yes. I tried from playground.
https://play.golang.org/p/AMhf-IQDLF4
What operating system and processor architecture are you using (
go env)?go envOutputWhat did you do?
I have struct that has int64 and byte type. When byte type variable is in the middle of other types in struct , the offset function does not show the proper offset(see link below)
https://play.golang.org/p/AMhf-IQDLF4
type custom struct {
a int64
b int64
c byte
d int64
e int64
f byte
g byte
}
the offset and address appropriately is
True 0 0xc000078030
True 8 0xc000078038
True 16 0xc000078040
False 24 0xc000078048 //But it should be 17 . 16+1 (a.c is byte type) =17
True 32 0xc000078050
True 40 0xc000078058
True 41 0xc000078059
What did you expect to see?
True 0 0xc0000a0000
True 8 0xc0000a0008
True 16 0xc0000a0010
True 17 0xc0000a0018
True 25 0xc0000a0020
True 33 0xc0000a0028
True 34 0xc0000a0029
What did you see instead?
True 0 0xc000078030
True 8 0xc000078038
True 16 0xc000078040
False 24 0xc000078048 //But it should be 17 . 16+1 (a.c is byte type) =17
True 32 0xc000078050
True 40 0xc000078058
True 41 0xc000078059
The text was updated successfully, but these errors were encountered: