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// Copyright 2016 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 runtime
import (
"runtime/internal/atomic"
_ "unsafe"
)
// For historical reasons these functions are called as though they
// were in the syscall package.
//go:linkname Cgocall syscall.Cgocall
//go:linkname CgocallDone syscall.CgocallDone
//go:linkname CgocallBack syscall.CgocallBack
//go:linkname CgocallBackDone syscall.CgocallBackDone
// A routine that may be called by SWIG.
//go:linkname _cgo_panic _cgo_panic
// iscgo is set to true if the cgo tool sets the C variable runtime_iscgo
// to true.
var iscgo bool
// cgoHasExtraM is set on startup when an extra M is created for cgo.
// The extra M must be created before any C/C++ code calls cgocallback.
var cgoHasExtraM bool
// Cgocall prepares to call from code written in Go to code written in
// C/C++. This takes the current goroutine out of the Go scheduler, as
// though it were making a system call. Otherwise the program can
// lookup if the C code blocks. The idea is to call this function,
// then immediately call the C/C++ function. After the C/C++ function
// returns, call cgocalldone. The usual Go code would look like
// syscall.Cgocall()
// defer syscall.Cgocalldone()
// cfunction()
func Cgocall() {
lockOSThread()
mp := getg().m
mp.ncgocall++
mp.ncgo++
entersyscall(0)
}
// CgocallDone prepares to return to Go code from C/C++ code.
func CgocallDone() {
gp := getg()
if gp == nil {
throw("no g in CgocallDone")
}
gp.m.ncgo--
// If we are invoked because the C function called _cgo_panic,
// then _cgo_panic will already have exited syscall mode.
if gp.atomicstatus == _Gsyscall {
exitsyscall(0)
}
unlockOSThread()
}
// CgocallBack is used when calling from C/C++ code into Go code.
// The usual approach is
// syscall.CgocallBack()
// defer syscall.CgocallBackDone()
// gofunction()
//go:nosplit
func CgocallBack() {
if getg() == nil || getg().m == nil {
needm(0)
mp := getg().m
mp.dropextram = true
}
exitsyscall(0)
if getg().m.ncgo == 0 {
// The C call to Go came from a thread created by C.
// The C call to Go came from a thread not currently running
// any Go. In the case of -buildmode=c-archive or c-shared,
// this call may be coming in before package initialization
// is complete. Wait until it is.
<-main_init_done
}
mp := getg().m
if mp.needextram || atomic.Load(&extraMWaiters) > 0 {
mp.needextram = false
newextram()
}
}
// CgocallBackDone prepares to return to C/C++ code that has called
// into Go code.
func CgocallBackDone() {
entersyscall(0)
mp := getg().m
if mp.dropextram && mp.ncgo == 0 {
mp.dropextram = false
dropm()
}
}
// _cgo_panic may be called by SWIG code to panic.
func _cgo_panic(p *byte) {
exitsyscall(0)
panic(gostringnocopy(p))
}
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