github.com/aloncn/graphics-go@v0.0.1/src/runtime/cgo.go (about)

     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_malloc _cgo_malloc
    15  //go:linkname _cgo_free _cgo_free
    16  //go:linkname _cgo_thread_start _cgo_thread_start
    17  //go:linkname _cgo_sys_thread_create _cgo_sys_thread_create
    18  //go:linkname _cgo_notify_runtime_init_done _cgo_notify_runtime_init_done
    19  
    20  var (
    21  	_cgo_init                     unsafe.Pointer
    22  	_cgo_malloc                   unsafe.Pointer
    23  	_cgo_free                     unsafe.Pointer
    24  	_cgo_thread_start             unsafe.Pointer
    25  	_cgo_sys_thread_create        unsafe.Pointer
    26  	_cgo_notify_runtime_init_done unsafe.Pointer
    27  )
    28  
    29  // iscgo is set to true by the runtime/cgo package
    30  var iscgo bool
    31  
    32  // cgoHasExtraM is set on startup when an extra M is created for cgo.
    33  // The extra M must be created before any C/C++ code calls cgocallback.
    34  var cgoHasExtraM bool
    35  
    36  // cgoUse is called by cgo-generated code (using go:linkname to get at
    37  // an unexported name). The calls serve two purposes:
    38  // 1) they are opaque to escape analysis, so the argument is considered to
    39  // escape to the heap.
    40  // 2) they keep the argument alive until the call site; the call is emitted after
    41  // the end of the (presumed) use of the argument by C.
    42  // cgoUse should not actually be called (see cgoAlwaysFalse).
    43  func cgoUse(interface{}) { throw("cgoUse should not be called") }
    44  
    45  // cgoAlwaysFalse is a boolean value that is always false.
    46  // The cgo-generated code says if cgoAlwaysFalse { cgoUse(p) }.
    47  // The compiler cannot see that cgoAlwaysFalse is always false,
    48  // so it emits the test and keeps the call, giving the desired
    49  // escape analysis result. The test is cheaper than the call.
    50  var cgoAlwaysFalse bool