reflect: unexport FFICallbackGo; use go:linkname instead

    
    The function was always intended to be internal-only, but was exported
    so that C code could call it. Now that have go:linkname for that, use it.
    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/195857

From-SVN: r275809

gcc/go/gofrontend/MERGE

-722990deeede7801e4ed3ca5d53ce312a19fcd7a
+ff18e041624b8c23ffcd747f51e9dda945777d2a
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

libgo/go/reflect/makefunc_ffi.go

@@ -15,19 +15,20 @@ func makeFuncFFI(cif unsafe.Pointer, impl unsafe.Pointer)
 // The makeCIF function, implemented in the runtime package, allocates a CIF.
 func makeCIF(ft *funcType) unsafe.Pointer
 
-// FFICallbackGo implements the Go side of the libffi callback.
-// It is exported so that C code can call it.
+// Export ffiCallbackGo so that C code in makefunc_ffi_c.c can call it.
+//go:linkname ffiCallbackGo
+
+// ffiCallbackGo implements the Go side of the libffi callback.
 //
 // The call chain arriving here looks like
 //   some_go_caller
 //   ->some_ffi_internals
 //     ->ffi_callback (in C)
-//       ->FFICallbackGo
+//       ->ffiCallbackGo
 //
 // The ffi_callback handles __go_makefunc_can_recover, and
 // then passes off the data as received from ffi here.
-
-func FFICallbackGo(results unsafe.Pointer, params unsafe.Pointer, impl *makeFuncImpl) {
+func ffiCallbackGo(results unsafe.Pointer, params unsafe.Pointer, impl *makeFuncImpl) {
 	ftyp := impl.typ
 	in := make([]Value, 0, len(ftyp.in))
 	ap := params

libgo/go/reflect/makefunc_ffi_c.c

@@ -25,8 +25,8 @@ void makeFuncFFI(void *cif, void *impl)
    function ffiCall with the pointer to the arguments, the results area,
    and the closure structure.  */
 
-extern void FFICallbackGo(void *result, void **args, ffi_go_closure *closure)
-  __asm__ (GOSYM_PREFIX "reflect.FFICallbackGo");
+extern void ffiCallbackGo(void *result, void **args, ffi_go_closure *closure)
+  __asm__ (GOSYM_PREFIX "reflect.ffiCallbackGo");
 
 extern void makefuncfficanrecover(Slice)
   __asm__ (GOSYM_PREFIX "runtime.makefuncfficanrecover");
@@ -72,7 +72,7 @@ ffi_callback (ffi_cif* cif __attribute__ ((unused)), void *results,
       makefuncfficanrecover (s);
     }
 
-  FFICallbackGo(results, args, closure);
+  ffiCallbackGo(results, args, closure);
 
   if (i < n)
     makefuncreturning ();