Cherry-pick from upstream: 6964d3a: Reload exception pointer register…

… in caml_c_call* - unclear which PR this is from

(cherry picked from commit ebfbd52)

ocaml/runtime/arm64.S

@@ -600,8 +600,9 @@ FUNCTION(caml_c_call)
         str     TRAP_PTR, Caml_state(exn_handler)
     /* Call the function */
         blr     ADDITIONAL_ARG
-    /* Reload alloc ptr  */
+    /* Reload new allocation pointer & exn handler */
         ldr     ALLOC_PTR, Caml_state(young_ptr)
+        ldr     TRAP_PTR, Caml_state(exn_handler)
     /* Load ocaml stack */
         SWITCH_C_TO_OCAML
 #if defined(WITH_THREAD_SANITIZER)
@@ -657,8 +658,9 @@ FUNCTION(caml_c_call_stack_args)
         blr     ADDITIONAL_ARG
     /* Restore stack */
         mov     sp, x19
-    /* Reload alloc ptr */
+    /* Reload new allocation pointer & exn handler */
         ldr     ALLOC_PTR, Caml_state(young_ptr)
+        ldr     TRAP_PTR, Caml_state(exn_handler)
     /* Switch from C to OCaml */
         SWITCH_C_TO_OCAML
     /* Return */

ocaml/testsuite/tests/callback/test1.ml

@@ -28,6 +28,9 @@ external mycallback3 : ('a -> 'b -> 'c -> 'd) -> 'a -> 'b -> 'c -> 'd
 external mycallback4 :
     ('a -> 'b -> 'c -> 'd -> 'e) -> 'a -> 'b -> 'c -> 'd -> 'e = "mycallback4"
 
+let rec growstack n =
+  if n <= 0 then 0 else 1 + growstack (n - 1)
+
 let rec tak (x, y, z as _tuple) =
   if x > y then tak(tak (x-1, y, z), tak (y-1, z, x), tak (z-1, x, y))
            else z
@@ -63,3 +66,5 @@ let _ =
   print_int(trapexit ()); print_newline();
   print_string(tripwire mypushroot); print_newline();
   print_string(tripwire mycamlparam); print_newline();
+  begin try ignore (mycallback1 growstack 1_000); raise Exit
+  with Exit -> () end