Remove root_jmpbuf in rb_thread_struct

It has not been used since 1b82c877df.

cont.c

@@ -711,8 +711,6 @@ fiber_pool_stack_release(struct fiber_pool_stack * stack)
 #endif
 }
 
-void rb_fiber_start(rb_fiber_t*);
-
 static inline void
 ec_switch(rb_thread_t *th, rb_fiber_t *fiber)
 {

eval.c

@@ -1112,17 +1112,14 @@ rb_protect(VALUE (* proc) (VALUE), VALUE data, int *pstate)
     volatile enum ruby_tag_type state;
     rb_execution_context_t * volatile ec = GET_EC();
     rb_control_frame_t *volatile cfp = ec->cfp;
-    rb_jmpbuf_t org_jmpbuf;
 
     EC_PUSH_TAG(ec);
-    MEMCPY(&org_jmpbuf, &rb_ec_thread_ptr(ec)->root_jmpbuf, rb_jmpbuf_t, 1);
     if ((state = EC_EXEC_TAG()) == TAG_NONE) {
 	SAVE_ROOT_JMPBUF(rb_ec_thread_ptr(ec), result = (*proc) (data));
     }
     else {
 	rb_vm_rewind_cfp(ec, cfp);
     }
-    MEMCPY(&rb_ec_thread_ptr(ec)->root_jmpbuf, &org_jmpbuf, rb_jmpbuf_t, 1);
     EC_POP_TAG();
 
     if (pstate != NULL) *pstate = state;

eval_intern.h

@@ -91,40 +91,12 @@ extern int select_large_fdset(int, fd_set *, fd_set *, fd_set *, struct timeval
 
 #include <sys/stat.h>
 
-#ifdef _MSC_VER
-#define SAVE_ROOT_JMPBUF_BEFORE_STMT \
-    __try {
-#define SAVE_ROOT_JMPBUF_AFTER_STMT \
-    } \
-    __except (GetExceptionCode() == EXCEPTION_STACK_OVERFLOW ? \
-	      (rb_ec_raised_set(GET_EC(), RAISED_STACKOVERFLOW), \
-	       raise(SIGSEGV), \
-	       EXCEPTION_EXECUTE_HANDLER) : \
-	      EXCEPTION_CONTINUE_SEARCH) { \
-	/* never reaches here */ \
-    }
-#elif defined(__MINGW32__)
-LONG WINAPI rb_w32_stack_overflow_handler(struct _EXCEPTION_POINTERS *);
-#define SAVE_ROOT_JMPBUF_BEFORE_STMT \
-    do { \
-	PVOID _handler = AddVectoredExceptionHandler(1, rb_w32_stack_overflow_handler);
-
-#define SAVE_ROOT_JMPBUF_AFTER_STMT \
-	RemoveVectoredExceptionHandler(_handler); \
-    } while (0);
-#else
-#define SAVE_ROOT_JMPBUF_BEFORE_STMT
-#define SAVE_ROOT_JMPBUF_AFTER_STMT
-#endif
 
 #define SAVE_ROOT_JMPBUF(th, stmt) do \
-  if (ruby_setjmp((th)->root_jmpbuf) == 0) { \
-      SAVE_ROOT_JMPBUF_BEFORE_STMT \
+  if (true) { \
       stmt; \
-      SAVE_ROOT_JMPBUF_AFTER_STMT \
   } \
-  else { \
-      rb_fiber_start(th->ec->fiber_ptr); \
+  else if (th) { /* suppress unused-variable warning */ \
   } while (0)
 
 #define EC_PUSH_TAG(ec) do { \

vm_core.h

@@ -1023,7 +1023,6 @@ typedef struct rb_thread_struct {
 
     /* fiber */
     rb_fiber_t *root_fiber;
-    rb_jmpbuf_t root_jmpbuf;
 
     VALUE scheduler;
     unsigned blocking;