[runtime.Pinner].

The _GoString_ type also may not be pinned with [runtime.Pinner].
Because it includes a Go pointer, the memory it points to is only pinned
for the duration of the call; _GoString_ values may not be retained by C
code.

A Go function called by C code may return a Go pointer to pinned memory
(which implies that it may not return a string, slice, channel, and so
forth). A Go function called by C code may take C pointers as arguments,

// Copyright Istio Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,

// Copyright Istio Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,