u3: removes/disables obsolete road stack overflow checks

pkg/urbit/include/noun/allocate.h

@@ -397,14 +397,10 @@
           u3a_push(const u3a_pile* pil_u)
           {
             u3R->cap_p += pil_u->mov_ws;
-            return u3a_peek(pil_u);
-          }
 
-        /* u3a_pile_sane(): bail on invalid road stack state.
+            //  XX define symbol to control guard page
-        */
+            //
-          inline void
+#if 0
-          u3a_pile_sane(const u3a_pile* pil_u)
-          {
             //  !off means we're on a north road
             //
             if ( !pil_u->off_ws ) {
@@ -423,10 +419,13 @@
               c3_assert( pil_u->top_p <= u3R->cap_p );
   #endif
             }
+#endif
 
 #ifdef U3_MEMORY_DEBUG
             c3_assert( pil_u->rod_u == u3R );
 #endif
+
+            return u3a_peek(pil_u);
           }
 
         /* u3a_pile_done(): assert valid upon completion.
@@ -708,14 +707,6 @@
                         void     (*pat_f)(u3_atom, void*),
                         c3_o     (*cel_f)(u3_noun, void*));
 
-        /* u3a_walk_fore_unsafe(): u3a_walk_fore(), without overflow checks
-        */
-          void
-          u3a_walk_fore_unsafe(u3_noun    a,
-                               void*      ptr_v,
-                               void     (*pat_f)(u3_atom, void*),
-                               c3_o     (*cel_f)(u3_noun, void*));
-
         /* u3a_string(): `a` as an on-loom c-string.
         */
           c3_c*

pkg/urbit/jets/b/reel.c

@@ -27,7 +27,6 @@
         *top = i;
       } while ( u3_nul != t );
 
-      u3a_pile_sane(&pil_u);
       u3j_gate_prep(&sit_u, u3k(b));
 
       while ( c3n == u3a_pile_done(&pil_u) ) {

pkg/urbit/jets/e/parse.c

@@ -984,10 +984,6 @@
       u3j_site raq_u;
       u3j_gate_prep(&raq_u, u3k(raq));
 
-      //  check for stack overflow
-      //
-      u3a_pile_sane(&pil_u);
-
       while ( c3n == u3a_pile_done(&pil_u) ) {
         p_wag   = _last_k(par_u->har, p_wag);
         puq_wag = u3j_gate_slam(&raq_u, u3nc(par_u->res, puq_wag));

pkg/urbit/noun/allocate.c

@@ -13,8 +13,6 @@ void*
 u3a_pop(const u3a_pile* pil_u);
 void*
 u3a_push(const u3a_pile* pil_u);
-void
-u3a_pile_sane(const u3a_pile* pil_u);
 c3_o
 u3a_pile_done(const u3a_pile* pil_u);
 
@@ -1176,7 +1174,6 @@ _ca_take_next_north(u3a_pile* pil_u, u3_noun veb)
       else {
         u3a_cell* old_u = (u3a_cell*)veb_u;
         _ca_take* fam_u = u3a_push(pil_u);
-        u3a_pile_sane(pil_u);
 
         fam_u->hed = u3_none;
         fam_u->old = veb;
@@ -1232,7 +1229,6 @@ _ca_take_next_south(u3a_pile* pil_u, u3_noun veb)
       else {
         u3a_cell* old_u = (u3a_cell*)veb_u;
         _ca_take* fam_u = u3a_push(pil_u);
-        u3a_pile_sane(pil_u);
 
         fam_u->hed = u3_none;
         fam_u->old = veb;
@@ -2656,50 +2652,6 @@ u3a_walk_fore(u3_noun    a,
     else {
       *top = u3t(a);
       top  = u3a_push(&pil_u);
-      u3a_pile_sane(&pil_u);
-      *top = u3h(a);
-    }
-
-    a = *top;
-  }
-}
-
-/* u3a_walk_fore_unsafe(): u3a_walk_fore(), without overflow checks
-*/
-void
-u3a_walk_fore_unsafe(u3_noun    a,
-                     void*      ptr_v,
-                     void     (*pat_f)(u3_atom, void*),
-                     c3_o     (*cel_f)(u3_noun, void*))
-{
-  u3_noun*   top;
-  u3a_pile pil_u;
-
-  //  initialize stack control; push argument
-  //
-  u3a_pile_prep(&pil_u, sizeof(u3_noun));
-  top  = u3a_push(&pil_u);
-  *top = a;
-
-  while ( c3n == u3a_pile_done(&pil_u) ) {
-    //  visit an atom, then pop the stack
-    //
-    if ( c3y == u3a_is_atom(a) ) {
-      pat_f(a, ptr_v);
-      top = u3a_pop(&pil_u);
-    }
-    //  vist a cell, if c3n, pop the stack
-    //
-    else if ( c3n == cel_f(a, ptr_v) ) {
-      top = u3a_pop(&pil_u);
-    }
-    //  otherwise, push the tail and continue into the head
-    //
-    else {
-      *top = u3t(a);
-      //  NB: overflow check elided here
-      //
-      top  = u3a_push(&pil_u);
       *top = u3h(a);
     }
 

pkg/urbit/noun/nock.c

@@ -1444,7 +1444,8 @@ _n_push(c3_ys mov, c3_ys off, u3_noun a)
 {
   u3R->cap_p += mov;
 
-  //  XX stack sanity-check disabled for performance
+  //  XX define symbol to control guard page
+  //  or switch to u3a_push()
   //
 #if 0
   if ( 0 == off ) {

pkg/urbit/noun/retrieve.c

@@ -1732,10 +1732,6 @@ _cr_mug_next(u3a_pile* pil_u, u3_noun veb)
         u3a_cell* cel_u = (u3a_cell*)veb_u;
         _cr_mugf* fam_u = u3a_push(pil_u);
 
-        //  check for overflow
-        //
-        u3a_pile_sane(pil_u);
-
         fam_u->mug_l = 0;
         fam_u->cel   = veb;
 

pkg/urbit/noun/serial.c

@@ -158,15 +158,9 @@ u3s_jam_fib(u3i_slab* sab_u, u3_noun a)
   fib_u.bit_w = 0;
   u3i_slab_init(sab_u, 0, fib_u.a_w);
 
-  //  as this is a hot path, we unsafely elide overflow checks
+  u3a_walk_fore(a, &fib_u, _cs_jam_fib_atom_cb, _cs_jam_fib_cell_cb);
-  //
-  //    a page-fault overflow detection system is urgently needed ...
-  //
-  u3a_walk_fore_unsafe(a, &fib_u, _cs_jam_fib_atom_cb,
-                                  _cs_jam_fib_cell_cb);
 
   u3h_free(fib_u.har_p);
-
   return fib_u.bit_w;
 }
 
@@ -270,18 +264,11 @@ u3s_jam_xeno(u3_noun a, c3_d* len_d, c3_y** byt_y)
 {
   _jam_xeno_t jam_u = {0};
   ur_bsw_init(&jam_u.rit_u, ur_fib11, ur_fib12);
-
   jam_u.har_p = u3h_new();
 
-  //  as this is a hot path, we unsafely elide overflow checks
+  u3a_walk_fore(a, &jam_u, _cs_jam_xeno_atom, _cs_jam_xeno_cell);
-  //
-  //    a page-fault overflow detection system is urgently needed ...
-  //
-  u3a_walk_fore_unsafe(a, &jam_u, _cs_jam_xeno_atom,
-                                  _cs_jam_xeno_cell);
 
   u3h_free(jam_u.har_p);
-
   return ur_bsw_done(&jam_u.rit_u, len_d, byt_y);
 }
 
@@ -360,7 +347,6 @@ _cs_cue_next(u3a_pile*     pil_u,
       //
       else {
         _cs_cue* fam_u = u3a_push(pil_u);
-        u3a_pile_sane(pil_u);
 
         //  NB: fam_u->wid unused in head-frame
         //
@@ -472,7 +458,6 @@ _cs_cue_xeno_next(u3a_pile*    pil_u,
 
       case ur_jam_cell: {
         _cue_frame_t* fam_u = u3a_push(pil_u);
-        u3a_pile_sane(pil_u);
 
         fam_u->ref   = u3_none;
         fam_u->bit_d = bit_d;
@@ -731,7 +716,6 @@ _cs_cue_bytes_next(u3a_pile*     pil_u,
 
       case ur_jam_cell: {
         _cue_frame_t* fam_u = u3a_push(pil_u);
-        u3a_pile_sane(pil_u);
 
         fam_u->ref   = u3_none;
         fam_u->bit_d = bit_d;