From: Ian Lance Taylor <iant@golang.org>
Date: Mon, 7 Jul 2025 20:01:34 +0000 (-0700)
Subject: cmd/compile: document that nosplit directive is unsafe
X-Git-Tag: go1.25rc3~5^2~43
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=bb917bb0303843467e809a3a373e4bb2d359fcfa;p=gostls13.git

cmd/compile: document that nosplit directive is unsafe

For #74478

Change-Id: I902e9a92cdacb5ad6dafa9896640f8196ba1d56a
Reviewed-on: https://go-review.googlesource.com/c/go/+/686115
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
---

diff --git a/src/cmd/compile/doc.go b/src/cmd/compile/doc.go
index f76f402f38..81e6189a26 100644
--- a/src/cmd/compile/doc.go
+++ b/src/cmd/compile/doc.go
@@ -253,6 +253,9 @@ The //go:nosplit directive must be followed by a function declaration.
 It specifies that the function must omit its usual stack overflow check.
 This is most commonly used by low-level runtime code invoked
 at times when it is unsafe for the calling goroutine to be preempted.
+Using this directive outside of low-level runtime code is not safe,
+because it permits the nosplit function to overwrite the end of stack,
+leading to memory corruption and arbitrary program failure.
 
 # Linkname Directive