strings: re-introduce noescape wrapper

CL 573955 added internal/abi:NoEscape function, and use it in strings
builder copyCheck code.

However, internal/abi is a runtime package, which can not be built with
-d=checkptr flag yet. This causes incorrect inlining decision, since
NoEscape must not be inlined when -d=checkptr is used.

Fixing this by re-introducing noescape wrapper.

Fixes #68415

Change-Id: I776cab4c9e9e4b3e58162dcce6ec025cb366bdee
Reviewed-on: https://go-review.googlesource.com/c/go/+/598295
Reviewed-by: Michael Knyszek <[email protected]>
Reviewed-by: Jorropo <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Keith Randall <[email protected]>
Auto-Submit: Cuong Manh Le <[email protected]>

src/strings/builder.go

@@ -23,14 +23,26 @@ type Builder struct {
 	buf []byte
 }
 
+// This is just a wrapper around abi.NoEscape.
+//
+// This wrapper is necessary because internal/abi is a runtime package,
+// so it can not be built with -d=checkptr, causing incorrect inlining
+// decision when building with checkptr enabled, see issue #68415.
+//
+//go:nosplit
+//go:nocheckptr
+func noescape(p unsafe.Pointer) unsafe.Pointer {
+	return abi.NoEscape(p)
+}
+
 func (b *Builder) copyCheck() {
 	if b.addr == nil {
 		// This hack works around a failing of Go's escape analysis
 		// that was causing b to escape and be heap allocated.
 		// See issue 23382.
 		// TODO: once issue 7921 is fixed, this should be reverted to
 		// just "b.addr = b".
-		b.addr = (*Builder)(abi.NoEscape(unsafe.Pointer(b)))
+		b.addr = (*Builder)(noescape(unsafe.Pointer(b)))
 	} else if b.addr != b {
 		panic("strings: illegal use of non-zero Builder copied by value")
 	}

test/fixedbugs/issue68415.go

@@ -0,0 +1,15 @@
+// run -gcflags=all=-d=checkptr
+
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import "regexp"
+
+var dataFileRegexp = regexp.MustCompile(`^data\.\d+\.bin$`)
+
+func main() {
+	_ = dataFileRegexp
+}