The Go programming language
Go to file
Michael Anthony Knyszek d87878c62b runtime: make special offset a uintptr
Currently specials try to save on space by only encoding the offset from
the base of the span in a uint16. This worked fine up until Go 1.24.
- Most specials have an offset of 0 (mem profile, finalizers, etc.)
- Cleanups do not care about the offset at all, so even if it's wrong,
  it's OK.
- Weak pointers *do* care, but the unique package always makes a new
  allocation, so the weak pointer handle offset it makes is always zero.

With Go 1.24 and general weak pointers now available, nothing is
stopping someone from just creating a weak pointer that is >64 KiB
offset from the start of an object, and this weak pointer must be
distinct from others.

Fix this problem by just increasing the size of a special and making the
offset a uintptr, to capture all possible offsets. Since we're in the
freeze, this is the safest thing to do. Specials aren't so common that I
expect a substantial memory increase from this change. In a future
release (or if there is a problem) we can almost certainly pack the
special's kind and offset together. There was already a bunch of wasted
space due to padding, so this would bring us back to the same memory
footprint before this change.

Also, add tests for equality of basic weak interior pointers. This
works, but we really should've had tests for it.

Fixes #70739.

Change-Id: Ib49a7f8f0f1ec3db4571a7afb0f4d94c8a93aa40
Reviewed-on: https://go-review.googlesource.com/c/go/+/634598
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Auto-Submit: Michael Knyszek <mknyszek@google.com>
Commit-Queue: Michael Knyszek <mknyszek@google.com>
2024-12-09 21:38:18 +00:00
.github .github: update language change proposal template 2024-08-08 19:02:29 +00:00
api api: promote next to go1.24 2024-12-05 21:40:08 +00:00
doc doc/next: delete 2024-12-05 22:41:12 +00:00
lib lib/wasm: provide fs.constants.O_DIRECTORY definition 2024-12-08 15:34:47 +00:00
misc misc/wasm: move wasm runtime files to lib/wasm 2024-08-30 19:15:21 +00:00
src runtime: make special offset a uintptr 2024-12-09 21:38:18 +00:00
test cmd/internal/objabi, internal/runtime: increase nosplit limit on OpenBSD 2024-12-06 00:35:41 +00:00
.gitattributes
.gitignore runtime,internal: move runtime/internal/sys to internal/runtime/sys 2024-07-23 19:05:35 +00:00
CONTRIBUTING.md
LICENSE LICENSE: update per Google Legal 2024-08-09 14:54:31 +00:00
PATENTS
README.md README: fix CC BY license name 2024-07-22 17:45:27 +00:00
SECURITY.md
codereview.cfg
go.env

README.md

The Go Programming Language

Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.

Gopher image Gopher image by Renee French, licensed under Creative Commons 4.0 Attribution license.

Our canonical Git repository is located at https://go.googlesource.com/go. There is a mirror of the repository at https://github.com/golang/go.

Unless otherwise noted, the Go source files are distributed under the BSD-style license found in the LICENSE file.

Download and Install

Binary Distributions

Official binary distributions are available at https://go.dev/dl/.

After downloading a binary release, visit https://go.dev/doc/install for installation instructions.

Install From Source

If a binary distribution is not available for your combination of operating system and architecture, visit https://go.dev/doc/install/source for source installation instructions.

Contributing

Go is the work of thousands of contributors. We appreciate your help!

To contribute, please read the contribution guidelines at https://go.dev/doc/contribute.

Note that the Go project uses the issue tracker for bug reports and proposals only. See https://go.dev/wiki/Questions for a list of places to ask questions about the Go language.