Unified `pc` and `err` of `mrb_callinfo`

This enhances self-containment.

- Changed the `mrb_callinfo::pc` field to point to itself.
  Previously it indicated the return destination of the previous call level.
  `mrb_callinfo::pc` will now hold the address to its own `proc->body.irep->iseq`.
- Removed `mrb_callinfo::err` field.
  This is because `mrb_callinfo::pc - 1` is semantically the same as the previous `err`.
- The `pc0` and `pc_save` variables in `mrb_vm_exec()` are no longer needed and have been deleted.
- It removes the argument because `cipush()` doesn't need to save the previous `pc`.

2 files changed, 8 insertions, 2 deletions

diff --git a/include/mruby.h b/include/mruby.h
index 3f78e66c6..b54e4f98e 100644
--- a/include/mruby.h
+++ b/include/mruby.h
@@ -152,8 +152,7 @@ typedef struct {
   mrb_sym mid;
   const struct RProc *proc;
   mrb_value *stack;
-  const mrb_code *pc;           /* return address */
-  const mrb_code *err;          /* error position */
+  const mrb_code *pc;           /* current address on iseq of this proc */
   int16_t argc;
   int16_t acc;
   union {
diff --git a/include/mruby/proc.h b/include/mruby/proc.h
index b4d0927a9..be45a06d8 100644
--- a/include/mruby/proc.h
+++ b/include/mruby/proc.h
@@ -136,6 +136,13 @@ MRB_API mrb_value mrb_proc_cfunc_env_get(mrb_state *mrb, mrb_int idx);
 
 MRB_API mrb_value mrb_load_proc(mrb_state *mrb, const struct RProc *proc);
 
+static inline void
+mrb_vm_ci_proc_set(mrb_callinfo *ci, const struct RProc *p)
+{
+  ci->proc = p;
+  ci->pc = (p && !MRB_PROC_CFUNC_P(p)) ? p->body.irep->iseq : NULL;
+}
+
 static inline struct RClass *
 mrb_vm_ci_target_class(const mrb_callinfo *ci)
 {