all: document legacy //go:linkname for modules with ≥200 dependents

Ignored these linknames which have not worked for a while:

github.com/xtls/xray-core:
	context.newCancelCtx removed in CL 463999 (Feb 2023)

github.com/u-root/u-root:
	funcPC removed in CL 513837 (Jul 2023)

tinygo.org/x/drivers:
	net.useNetdev never existed

For #67401.

Change-Id: I9293f4ef197bb5552b431de8939fa94988a060ce
Reviewed-on: https://go-review.googlesource.com/c/go/+/587576
Auto-Submit: Russ Cox <rsc@golang.org>
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/src/runtime/string.go b/src/runtime/string.go
index d45888b7a8..5bdb25b9db 100644
--- a/src/runtime/string.go
+++ b/src/runtime/string.go
@@ -78,6 +78,16 @@ func concatstring5(buf *tmpBuf, a0, a1, a2, a3, a4 string) string {
 // n is the length of the slice.
 // Buf is a fixed-size buffer for the result,
 // it is not nil if the result does not escape.
+//
+// slicebytetostring should be an internal detail,
+// but widely used packages access it using linkname.
+// Notable members of the hall of shame include:
+//   - github.com/cloudwego/frugal
+//
+// Do not remove or change the type signature.
+// See go.dev/issue/67401.
+//
+//go:linkname slicebytetostring
 func slicebytetostring(buf *tmpBuf, ptr *byte, n int) string {
 	if n == 0 {
 		// Turns out to be a relatively common case.