1// Copyright 2014 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5package runtime
6
7import "unsafe"
8
9//go:cgo_export_static main
10
11// Filled in by runtime/cgo when linked into binary.
12
13//go:linkname _cgo_init _cgo_init
14//go:linkname _cgo_thread_start _cgo_thread_start
15//go:linkname _cgo_sys_thread_create _cgo_sys_thread_create
16//go:linkname _cgo_notify_runtime_init_done _cgo_notify_runtime_init_done
17//go:linkname _cgo_callers _cgo_callers
18//go:linkname _cgo_set_context_function _cgo_set_context_function
19//go:linkname _cgo_yield _cgo_yield
20
21var (
22	_cgo_init                     unsafe.Pointer
23	_cgo_thread_start             unsafe.Pointer
24	_cgo_sys_thread_create        unsafe.Pointer
25	_cgo_notify_runtime_init_done unsafe.Pointer
26	_cgo_callers                  unsafe.Pointer
27	_cgo_set_context_function     unsafe.Pointer
28	_cgo_yield                    unsafe.Pointer
29)
30
31// iscgo is set to true by the runtime/cgo package
32var iscgo bool
33
34// cgoHasExtraM is set on startup when an extra M is created for cgo.
35// The extra M must be created before any C/C++ code calls cgocallback.
36var cgoHasExtraM bool
37
38// cgoUse is called by cgo-generated code (using go:linkname to get at
39// an unexported name). The calls serve two purposes:
40// 1) they are opaque to escape analysis, so the argument is considered to
41// escape to the heap.
42// 2) they keep the argument alive until the call site; the call is emitted after
43// the end of the (presumed) use of the argument by C.
44// cgoUse should not actually be called (see cgoAlwaysFalse).
45func cgoUse(interface{}) { throw("cgoUse should not be called") }
46
47// cgoAlwaysFalse is a boolean value that is always false.
48// The cgo-generated code says if cgoAlwaysFalse { cgoUse(p) }.
49// The compiler cannot see that cgoAlwaysFalse is always false,
50// so it emits the test and keeps the call, giving the desired
51// escape analysis result. The test is cheaper than the call.
52var cgoAlwaysFalse bool
53
54var cgo_yield = &_cgo_yield
55