fix a prompt bug

* libguile/control.h:
* libguile/control.c (scm_c_make_prompt): Instead of taking a VM arg,
  take the registers directly.
  (scm_c_abort): Declare as returning void. In fact it will never
  return.

* libguile/eval.c (eval):
* libguile/throw.c (pre_init_catch): Adapt to prompt API change.

* libguile/vm-i-system.c (prompt): Pass the abort ip as the ip to
  scm_c_make_prompt. This fixes a bug in which we used the "offset"
  local var, but it wasn't guaranteed to be around after a longjmp.

libguile/control.c

@@ -32,8 +32,8 @@ SCM scm_sys_default_prompt_tag;
 
 
 SCM
-scm_c_make_prompt (SCM vm, SCM k, scm_t_uint8 escape_only_p,
+scm_c_make_prompt (SCM k, SCM *fp, SCM *sp, scm_t_uint8 *abort_ip,
-                   scm_t_int64 vm_cookie)
+                   scm_t_uint8 escape_only_p, scm_t_int64 vm_cookie)
 {
   scm_t_bits tag;
   SCM ret;
@@ -45,9 +45,9 @@ scm_c_make_prompt (SCM vm, SCM k, scm_t_uint8 escape_only_p,
   ret = scm_words (tag, 5);
 
   regs = scm_gc_malloc_pointerless (sizeof (*regs), "prompt registers");
-  regs->fp = SCM_VM_DATA (vm)->fp;
+  regs->fp = fp;
-  regs->sp = SCM_VM_DATA (vm)->sp;
+  regs->sp = sp;
-  regs->ip = SCM_VM_DATA (vm)->ip;
+  regs->ip = abort_ip;
   regs->cookie = vm_cookie;
 
   SCM_SET_CELL_OBJECT (ret, 1, k);
@@ -190,7 +190,7 @@ reify_partial_continuation (SCM vm, SCM prompt, SCM extwinds,
   return ret;
 }
 
-SCM
+void
 scm_c_abort (SCM vm, SCM tag, size_t n, SCM *argv, scm_t_int64 cookie)
 {
   SCM cont, winds, prompt = SCM_BOOL_F;

libguile/control.h

@@ -45,11 +45,13 @@ struct scm_prompt_registers
 SCM_INTERNAL SCM scm_sys_default_prompt_tag;
 
 
-SCM_INTERNAL SCM scm_c_make_prompt (SCM vm, SCM k, scm_t_uint8 escape_only_p,
+SCM_INTERNAL SCM scm_c_make_prompt (SCM k, SCM *fp, SCM *sp,
-                                    scm_t_int64 cookie);
+                                    scm_t_uint8 *abort_ip,
+                                    scm_t_uint8 escape_only_p,
+                                    scm_t_int64 vm_cookie);
 SCM_INTERNAL SCM scm_i_prompt_pop_abort_args_x (SCM prompt);
 
-SCM_INTERNAL SCM scm_c_abort (SCM vm, SCM tag, size_t n, SCM *argv,
+SCM_INTERNAL void scm_c_abort (SCM vm, SCM tag, size_t n, SCM *argv,
                                scm_t_int64 cookie) SCM_NORETURN;
 SCM_INTERNAL SCM scm_at_abort (SCM tag, SCM args) SCM_NORETURN;
 

libguile/eval.c

@@ -427,9 +427,12 @@ eval (SCM x, SCM env)
 
     case SCM_M_PROMPT:
       {
-        SCM prompt, handler, res;
+        SCM vm, prompt, handler, res;
 
-        prompt = scm_c_make_prompt (scm_the_vm (), eval (CAR (mx), env), 0, -1);
+        vm = scm_the_vm ();
+        prompt = scm_c_make_prompt (eval (CAR (mx), env), SCM_VM_DATA (vm)->fp,
+                                    SCM_VM_DATA (vm)->sp, SCM_VM_DATA (vm)->ip,
+                                    0, -1);
         handler = eval (CDDR (mx), env);
         scm_i_set_dynwinds (scm_cons (prompt, scm_i_dynwinds ()));
 

libguile/vm-i-system.c

@@ -1479,19 +1479,21 @@ VM_DEFINE_INSTRUCTION (83, prompt, "prompt", 4, 2, 0)
   POP (k);
 
   SYNC_REGISTER ();
-  /* Push the prompt onto the dynamic stack. The setjmp itself has to be local
+  /* Push the prompt onto the dynamic stack. */
-     to this procedure. */
+  prompt = scm_c_make_prompt (k, fp, sp, ip + offset, escape_only_p, vm_cookie);
-  /* FIXME: do more error checking */
-  prompt = scm_c_make_prompt (vm, k, escape_only_p, vm_cookie);
   scm_i_set_dynwinds (scm_cons (prompt, scm_i_dynwinds ()));
   if (SCM_PROMPT_SETJMP (prompt))
     {
       /* The prompt exited nonlocally. Cache the regs back from the vp, and go
          to the handler.
+
+         Note, at this point, we must assume that any variable local to
+         vm_engine that can be assigned *has* been assigned. So we need to pull
+         all our state back from the ip/fp/sp.
       */
-      CACHE_REGISTER (); /* Really we only need SP. FP and IP should be
+      CACHE_REGISTER ();
-                            unmodified. */
+      program = SCM_FRAME_PROGRAM (fp);
-      ip += offset;
+      CACHE_PROGRAM ();
       NEXT;
     }