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runtime: use the immortal weak handle map for sbrk mode

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Currently weak pointers break in sbrk mode. We can just use the immortal
weak handle map for weak pointers in this case, since nothing is ever
freed.

Fixes #69729.

Change-Id: Ie9fa7e203c22776dc9eb3601c6480107d9ad0c99
Reviewed-on: https://go-review.googlesource.com/c/go/+/674656
Reviewed-by: Carlos Amedee <carlos@golang.org>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
TryBot-Bypass: Michael Knyszek <mknyszek@google.com>
This commit is contained in:
Michael Anthony Knyszek 2025-05-20 20:56:46 +00:00 committed by Gopher Robot
parent 27ff0f249c
commit 53b9eae387
1 changed files with 10 additions and 0 deletions
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10
src/runtime/mheap.go
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@ -2545,6 +2545,16 @@ func gcWakeAllStrongFromWeak() {
// Retrieves or creates a weak pointer handle for the object p.
func getOrAddWeakHandle(p unsafe.Pointer) *atomic.Uintptr {
if debug.sbrk != 0 {
// debug.sbrk never frees memory, so it'll never go nil. However, we do still
// need a weak handle that's specific to p. Use the immortal weak handle map.
// Keep p alive across the call to getOrAdd defensively, though it doesn't
// really matter in this particular case.
handle := mheap_.immortalWeakHandles.getOrAdd(uintptr(p))
KeepAlive(p)
return handle
}
// First try to retrieve without allocating.
if handle := getWeakHandle(p); handle != nil {
// Keep p alive for the duration of the function to ensure