Source file src/runtime/cgo.go

     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  
     5  package runtime
     6  
     7  import "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  //go:linkname _cgo_pthread_key_created _cgo_pthread_key_created
    21  //go:linkname _cgo_bindm _cgo_bindm
    22  //go:linkname _cgo_getstackbound _cgo_getstackbound
    23  
    24  var (
    25  	_cgo_init                     unsafe.Pointer
    26  	_cgo_thread_start             unsafe.Pointer
    27  	_cgo_sys_thread_create        unsafe.Pointer
    28  	_cgo_notify_runtime_init_done unsafe.Pointer
    29  	_cgo_callers                  unsafe.Pointer
    30  	_cgo_set_context_function     unsafe.Pointer
    31  	_cgo_yield                    unsafe.Pointer
    32  	_cgo_pthread_key_created      unsafe.Pointer
    33  	_cgo_bindm                    unsafe.Pointer
    34  	_cgo_getstackbound            unsafe.Pointer
    35  )
    36  
    37  // iscgo is set to true by the runtime/cgo package
    38  var iscgo bool
    39  
    40  // set_crosscall2 is set by the runtime/cgo package
    41  var set_crosscall2 func()
    42  
    43  // cgoHasExtraM is set on startup when an extra M is created for cgo.
    44  // The extra M must be created before any C/C++ code calls cgocallback.
    45  var cgoHasExtraM bool
    46  
    47  // cgoUse is called by cgo-generated code (using go:linkname to get at
    48  // an unexported name). The calls serve two purposes:
    49  // 1) they are opaque to escape analysis, so the argument is considered to
    50  // escape to the heap.
    51  // 2) they keep the argument alive until the call site; the call is emitted after
    52  // the end of the (presumed) use of the argument by C.
    53  // cgoUse should not actually be called (see cgoAlwaysFalse).
    54  func cgoUse(any) { throw("cgoUse should not be called") }
    55  
    56  // cgoAlwaysFalse is a boolean value that is always false.
    57  // The cgo-generated code says if cgoAlwaysFalse { cgoUse(p) }.
    58  // The compiler cannot see that cgoAlwaysFalse is always false,
    59  // so it emits the test and keeps the call, giving the desired
    60  // escape analysis result. The test is cheaper than the call.
    61  var cgoAlwaysFalse bool
    62  
    63  var cgo_yield = &_cgo_yield
    64  
    65  func cgoNoCallback(v bool) {
    66  	g := getg()
    67  	if g.nocgocallback && v {
    68  		panic("runtime: unexpected setting cgoNoCallback")
    69  	}
    70  	g.nocgocallback = v
    71  }
    72  

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