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sync/atomic: clarify 64-bit alignment bug 

Local variables can also be relied on the be 64-bit aligned, since
they will be escaped to the heap if used with any atomic operations.

Also, allocated arrays are also aligned, just like structs and slices.

Fixes #18955.

Change-Id: I8a1897f6ff78922c8bfcf20d6eb4bcb17a70ba2d
Reviewed-on: https://go-review.googlesource.com/48112
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Austin Clements 2017-07-11 11:03:36 -04:00
parent 58ae050055
commit fea7c43ea2
1 changed files with 2 additions and 2 deletions
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4
src/sync/atomic/doc.go
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@ -48,8 +48,8 @@ import (
// On non-Linux ARM, the 64-bit functions use instructions unavailable before the ARMv6k core.
//
// On both ARM and x86-32, it is the caller's responsibility to arrange for 64-bit
// alignment of 64-bit words accessed atomically. The first word in a global
// variable or in an allocated struct or slice can be relied upon to be
// alignment of 64-bit words accessed atomically. The first word in a
// variable or in an allocated struct, array, or slice can be relied upon to be
// 64-bit aligned.
// SwapInt32 atomically stores new into *addr and returns the previous *addr value.