Correct macOS >= 10.13, Go >= 1.10 CoreFoundation pointer type errorsupdate-to-build-against-go1.14

When building the project on macOS 10.15 with Go 1.13, I ended up with
the following errors:

    # github.com/keybase/go-notifier
    ./corefoundation.go:25:9: cannot convert nil to type _Ctype_CFTypeRef
    ./corefoundation.go:34:3: cannot use nil as type _Ctype_CFDataRef in return argument
    ./corefoundation.go:40:26: cannot use nil as type _Ctype_CFAllocatorRef in argument to _Cfunc_CFDataCreate
    ./corefoundation.go:41:12: cannot convert nil to type _Ctype_CFDataRef
    ./corefoundation.go:42:3: cannot use nil as type _Ctype_CFDataRef in return argument
    ./corefoundation.go:66:47: cannot use nil as type _Ctype_CFAllocatorRef in assignment
    ./corefoundation.go:67:12: cannot convert nil to type _Ctype_CFDictionaryRef
    ./corefoundation.go:68:3: cannot use nil as type _Ctype_CFDictionaryRef in return argument
    ./corefoundation.go:79:59: cannot convert &(*_cgoIndex1)[0] (type *_Ctype_CFTypeRef) to type *unsafe.Pointer
    ./corefoundation.go:79:88: cannot convert &(*_cgoIndex2)[0] (type *_Ctype_CFTypeRef) to type *unsafe.Pointer
    ./corefoundation.go:92:3: cannot use nil as type _Ctype_CFStringRef in return argument
    ./corefoundation.go:95:3: cannot use nil as type _Ctype_CFStringRef in return argument
    ./corefoundation.go:103:34: cannot use nil as type _Ctype_CFAllocatorRef in argument to _Cfunc_CFStringCreateWithBytes
    ./corefoundation.go:138:39: cannot use nil as type _Ctype_CFAllocatorRef in assignment
    ./corefoundation.go:146:69: cannot convert &(*_cgoIndex2)[0] (type *_Ctype_CFTypeRef) to type *unsafe.Pointer
    ./corefoundation.go:157:4: cannot use nil as type _Ctype_CFArrayRef in return argument
    ./corefoundation.go:178:4: cannot use nil as type _Ctype_CFDictionaryRef in return argument
    ./corefoundation.go:190:5: cannot use nil as type _Ctype_CFDictionaryRef in return argument
    ./corefoundation.go:197:5: cannot use nil as type _Ctype_CFDictionaryRef in return argument
    ./corefoundation.go:204:5: cannot use nil as type _Ctype_CFDictionaryRef in return argument
    ./corefoundation.go:211:4: cannot use nil as type _Ctype_CFDictionaryRef in return argument
    ./corefoundation.go:218:3: cannot use nil as type _Ctype_CFDictionaryRef in return argument

    ./notifier_darwin.go:57:38: cannot use nil as type _Ctype_CFStringRef in assignment
    ./notifier_darwin.go:58:3: cannot use nil as type _Ctype_CFStringRef in assignment

Found similar errors reported on the 'fsevents' project:
https://github.com/fsnotify/fsevents/issues/33 ,
https://github.com/golang/go/issues/23317

It turns out that Cgo handles CoreFoundation types differently starting
in Go 1.10:

> Cgo now translates some C types that would normally map to a pointer
> type in Go, to a uintptr instead. These types include the CFTypeRef
> hierarchy in Darwin's CoreFoundation framework and the jobject
> hierarchy in Java's JNI interface.
>
> These types must be uintptr on the Go side because they would
> otherwise confuse the Go garbage collector; they are sometimes not
> really pointers but data structures encoded in a pointer-sized
> integer. Pointers to Go memory must not be stored in these uintptr
> values.
>
> Because of this change, values of the affected types need to be
> zero-initialized with the constant 0 instead of the constant nil.

https://tip.golang.org/doc/go1.10#cgo

For the "cannot convert" errors, use xlab's (https://github.com/xlab)
suggestion:

> The workaround is to pass it as ptr :=
> (*unsafe.Pointer)(unsafe.Pointer(arg)) which looks strange but works.

https://github.com/golang/go/issues/13830#issuecomment-169139332

1 files changed, 2 insertions, 2 deletions

diff --git a/notifier_darwin.go b/notifier_darwin.go
index e6f9c07..45d61f0 100644
--- a/notifier_darwin.go
+++ b/notifier_darwin.go
@@ -54,8 +54,8 @@ func (n darwinNotifier) DeliverNotification(notification Notification) error {
 	actionsRef := StringsToCFArray(notification.Actions)
 	defer Release(C.CFTypeRef(actionsRef))
 
-	C.deliverNotification(titleRef, nil, messageRef, appIconURLStringRef, actionsRef,
-		bundleIDRef, nil, C.NSTimeInterval(notification.Timeout), false)
+	C.deliverNotification(titleRef, 0, messageRef, appIconURLStringRef, actionsRef,
+		bundleIDRef, 0, C.NSTimeInterval(notification.Timeout), false)
 
 	return nil
 }