[dev.link] all: merge branch 'master' into dev.linkdev.link

Clean merge.

Change-Id: Ia7b2808bc649790198d34c226a61d9e569084dc5

1 files changed, 12 insertions, 17 deletions

diff --git a/src/runtime/cgo/callbacks.go b/src/runtime/cgo/callbacks.go
index 14a218ec92..cd8b795387 100644
--- a/src/runtime/cgo/callbacks.go
+++ b/src/runtime/cgo/callbacks.go
@@ -9,20 +9,18 @@ import "unsafe"
 // These utility functions are available to be called from code
 // compiled with gcc via crosscall2.
 
-// cgocallback is defined in runtime
-//go:linkname _runtime_cgocallback runtime.cgocallback
-func _runtime_cgocallback(unsafe.Pointer, unsafe.Pointer, uintptr, uintptr)
-
 // The declaration of crosscall2 is:
-//   void crosscall2(void (*fn)(void *, int), void *, int);
+//   void crosscall2(void (*fn)(void *), void *, int);
 //
 // We need to export the symbol crosscall2 in order to support
 // callbacks from shared libraries. This applies regardless of
 // linking mode.
 //
-// Compatibility note: crosscall2 actually takes four arguments, but
-// it works to call it with three arguments when calling _cgo_panic.
-// That is supported for backward compatibility.
+// Compatibility note: SWIG uses crosscall2 in exactly one situation:
+// to call _cgo_panic using the pattern shown below. We need to keep
+// that pattern working. In particular, crosscall2 actually takes four
+// arguments, but it works to call it with three arguments when
+// calling _cgo_panic.
 //go:cgo_export_static crosscall2
 //go:cgo_export_dynamic crosscall2
 
@@ -34,21 +32,18 @@ func _runtime_cgocallback(unsafe.Pointer, unsafe.Pointer, uintptr, uintptr)
 //   crosscall2(_cgo_panic, &a, sizeof a);
 //   /* The function call will not return.  */
 
+// TODO: We should export a regular C function to panic, change SWIG
+// to use that instead of the above pattern, and then we can drop
+// backwards-compatibility from crosscall2 and stop exporting it.
+
 //go:linkname _runtime_cgo_panic_internal runtime._cgo_panic_internal
 func _runtime_cgo_panic_internal(p *byte)
 
 //go:linkname _cgo_panic _cgo_panic
 //go:cgo_export_static _cgo_panic
 //go:cgo_export_dynamic _cgo_panic
-//go:nosplit
-//go:norace
-func _cgo_panic(a unsafe.Pointer, n int32) {
-	f := _runtime_cgo_panic_internal
-	type funcval struct {
-		pc unsafe.Pointer
-	}
-	fv := *(**funcval)(unsafe.Pointer(&f))
-	_runtime_cgocallback(fv.pc, a, uintptr(n), 0)
+func _cgo_panic(a *struct{ cstr *byte }) {
+	_runtime_cgo_panic_internal(a.cstr)
 }
 
 //go:cgo_import_static x_cgo_init