diff --git a/3rd/lua/lcode.c b/3rd/lua/lcode.c
index 6f241c94..14d41f1a 100644
--- a/3rd/lua/lcode.c
+++ b/3rd/lua/lcode.c
@@ -753,7 +753,7 @@ void luaK_setoneret (FuncState *fs, expdesc *e) {
 
 
 /*
-** Ensure that expression 'e' is not a variable (nor a constant).
+** Ensure that expression 'e' is not a variable (nor a <const>).
 ** (Expression still may have jump lists.)
 */
 void luaK_dischargevars (FuncState *fs, expdesc *e) {
@@ -805,8 +805,8 @@ void luaK_dischargevars (FuncState *fs, expdesc *e) {
 
 
 /*
-** Ensures expression value is in register 'reg' (and therefore
-** 'e' will become a non-relocatable expression).
+** Ensure expression value is in register 'reg', making 'e' a
+** non-relocatable expression.
 ** (Expression still may have jump lists.)
 */
 static void discharge2reg (FuncState *fs, expdesc *e, int reg) {
@@ -860,7 +860,8 @@ static void discharge2reg (FuncState *fs, expdesc *e, int reg) {
 
 
 /*
-** Ensures expression value is in any register.
+** Ensure expression value is in a register, making 'e' a
+** non-relocatable expression.
 ** (Expression still may have jump lists.)
 */
 static void discharge2anyreg (FuncState *fs, expdesc *e) {
@@ -946,8 +947,11 @@ int luaK_exp2anyreg (FuncState *fs, expdesc *e) {
       exp2reg(fs, e, e->u.info);  /* put final result in it */
       return e->u.info;
     }
+    /* else expression has jumps and cannot change its register
+       to hold the jump values, because it is a local variable.
+       Go through to the default case. */
   }
-  luaK_exp2nextreg(fs, e);  /* otherwise, use next available register */
+  luaK_exp2nextreg(fs, e);  /* default: use next available register */
   return e->u.info;
 }
 
diff --git a/3rd/lua/ldo.c b/3rd/lua/ldo.c
index 5729b190..a60972b2 100644
--- a/3rd/lua/ldo.c
+++ b/3rd/lua/ldo.c
@@ -534,11 +534,11 @@ CallInfo *luaD_precall (lua_State *L, StkId func, int nresults) {
 
 
 /*
-** Call a function (C or Lua). 'inc' can be 1 (increment number
-** of recursive invocations in the C stack) or nyci (the same plus
-** increment number of non-yieldable calls).
+** Call a function (C or Lua) through C. 'inc' can be 1 (increment
+** number of recursive invocations in the C stack) or nyci (the same
+** plus increment number of non-yieldable calls).
 */
-static void docall (lua_State *L, StkId func, int nResults, int inc) {
+static void ccall (lua_State *L, StkId func, int nResults, int inc) {
   CallInfo *ci;
   L->nCcalls += inc;
   if (unlikely(getCcalls(L) >= LUAI_MAXCCALLS))
@@ -552,10 +552,10 @@ static void docall (lua_State *L, StkId func, int nResults, int inc) {
 
 
 /*
-** External interface for 'docall'
+** External interface for 'ccall'
 */
 void luaD_call (lua_State *L, StkId func, int nResults) {
-  return docall(L, func, nResults, 1);
+  ccall(L, func, nResults, 1);
 }
 
 
@@ -563,7 +563,7 @@ void luaD_call (lua_State *L, StkId func, int nResults) {
 ** Similar to 'luaD_call', but does not allow yields during the call.
 */
 void luaD_callnoyield (lua_State *L, StkId func, int nResults) {
-  return docall(L, func, nResults, nyci);
+  ccall(L, func, nResults, nyci);
 }
 
 
@@ -678,7 +678,7 @@ static void resume (lua_State *L, void *ud) {
   StkId firstArg = L->top - n;  /* first argument */
   CallInfo *ci = L->ci;
   if (L->status == LUA_OK)  /* starting a coroutine? */
-    docall(L, firstArg - 1, LUA_MULTRET, 1);  /* just call its body */
+    ccall(L, firstArg - 1, LUA_MULTRET, 1);  /* just call its body */
   else {  /* resuming from previous yield */
     lua_assert(L->status == LUA_YIELD);
     L->status = LUA_OK;  /* mark that it is running (again) */
diff --git a/3rd/lua/llex.c b/3rd/lua/llex.c
index 3d6b2b97..4b8dec99 100644
--- a/3rd/lua/llex.c
+++ b/3rd/lua/llex.c
@@ -254,9 +254,10 @@ static int read_numeral (LexState *ls, SemInfo *seminfo) {
 
 
 /*
-** reads a sequence '[=*[' or ']=*]', leaving the last bracket.
-** If sequence is well formed, return its number of '='s + 2; otherwise,
-** return 1 if there is no '='s or 0 otherwise (an unfinished '[==...').
+** read a sequence '[=*[' or ']=*]', leaving the last bracket. If
+** sequence is well formed, return its number of '='s + 2; otherwise,
+** return 1 if it is a single bracket (no '='s and no 2nd bracket);
+** otherwise (an unfinished '[==...') return 0.
 */
 static size_t skip_sep (LexState *ls) {
   size_t count = 0;
@@ -481,34 +482,34 @@ static int llex (LexState *ls, SemInfo *seminfo) {
       }
       case '=': {
         next(ls);
-        if (check_next1(ls, '=')) return TK_EQ;
+        if (check_next1(ls, '=')) return TK_EQ;  /* '==' */
         else return '=';
       }
       case '<': {
         next(ls);
-        if (check_next1(ls, '=')) return TK_LE;
-        else if (check_next1(ls, '<')) return TK_SHL;
+        if (check_next1(ls, '=')) return TK_LE;  /* '<=' */
+        else if (check_next1(ls, '<')) return TK_SHL;  /* '<<' */
         else return '<';
       }
       case '>': {
         next(ls);
-        if (check_next1(ls, '=')) return TK_GE;
-        else if (check_next1(ls, '>')) return TK_SHR;
+        if (check_next1(ls, '=')) return TK_GE;  /* '>=' */
+        else if (check_next1(ls, '>')) return TK_SHR;  /* '>>' */
         else return '>';
       }
       case '/': {
         next(ls);
-        if (check_next1(ls, '/')) return TK_IDIV;
+        if (check_next1(ls, '/')) return TK_IDIV;  /* '//' */
         else return '/';
       }
       case '~': {
         next(ls);
-        if (check_next1(ls, '=')) return TK_NE;
+        if (check_next1(ls, '=')) return TK_NE;  /* '~=' */
         else return '~';
       }
       case ':': {
         next(ls);
-        if (check_next1(ls, ':')) return TK_DBCOLON;
+        if (check_next1(ls, ':')) return TK_DBCOLON;  /* '::' */
         else return ':';
       }
       case '"': case '\'': {  /* short literal strings */
@@ -547,7 +548,7 @@ static int llex (LexState *ls, SemInfo *seminfo) {
             return TK_NAME;
           }
         }
-        else {  /* single-char tokens (+ - / ...) */
+        else {  /* single-char tokens ('+', '*', '%', '{', '}', ...) */
           int c = ls->current;
           next(ls);
           return c;
diff --git a/3rd/lua/llimits.h b/3rd/lua/llimits.h
index d6866d7c..a76c13ed 100644
--- a/3rd/lua/llimits.h
+++ b/3rd/lua/llimits.h
@@ -355,7 +355,7 @@ typedef l_uint32 Instruction;
 #else
 /* realloc stack keeping its size */
 #define condmovestack(L,pre,pos)  \
-  { int sz_ = (L)->stacksize; pre; luaD_reallocstack((L), sz_, 0); pos; }
+  { int sz_ = stacksize(L); pre; luaD_reallocstack((L), sz_, 0); pos; }
 #endif
 
 #if !defined(HARDMEMTESTS)
diff --git a/3rd/lua/lparser.c b/3rd/lua/lparser.c
index bcdcfb6d..fb7a1264 100644
--- a/3rd/lua/lparser.c
+++ b/3rd/lua/lparser.c
@@ -945,7 +945,7 @@ static void setvararg (FuncState *fs, int nparams) {
 
 
 static void parlist (LexState *ls) {
-  /* parlist -> [ param { ',' param } ] */
+  /* parlist -> [ {NAME ','} (NAME | '...') ] */
   FuncState *fs = ls->fs;
   Proto *f = fs->f;
   int nparams = 0;
@@ -953,12 +953,12 @@ static void parlist (LexState *ls) {
   if (ls->t.token != ')') {  /* is 'parlist' not empty? */
     do {
       switch (ls->t.token) {
-        case TK_NAME: {  /* param -> NAME */
+        case TK_NAME: {
           new_localvar(ls, str_checkname(ls));
           nparams++;
           break;
         }
-        case TK_DOTS: {  /* param -> '...' */
+        case TK_DOTS: {
           luaX_next(ls);
           isvararg = 1;
           break;
@@ -1752,7 +1752,7 @@ static void checktoclose (LexState *ls, int level) {
 
 
 static void localstat (LexState *ls) {
-  /* stat -> LOCAL ATTRIB NAME {',' ATTRIB NAME} ['=' explist] */
+  /* stat -> LOCAL NAME ATTRIB { ',' NAME ATTRIB } ['=' explist] */
   FuncState *fs = ls->fs;
   int toclose = -1;  /* index of to-be-closed variable (if any) */
   Vardesc *var;  /* last variable */
diff --git a/3rd/lua/lparser.h b/3rd/lua/lparser.h
index 618cb010..2e6dae72 100644
--- a/3rd/lua/lparser.h
+++ b/3rd/lua/lparser.h
@@ -23,7 +23,7 @@
 
 /* kinds of variables/expressions */
 typedef enum {
-  VVOID,  /* when 'expdesc' describes the last expression a list,
+  VVOID,  /* when 'expdesc' describes the last expression of a list,
              this kind means an empty list (so, no expression) */
   VNIL,  /* constant nil */
   VTRUE,  /* constant true */
@@ -38,7 +38,8 @@ typedef enum {
   VLOCAL,  /* local variable; var.sidx = stack index (local register);
               var.vidx = relative index in 'actvar.arr'  */
   VUPVAL,  /* upvalue variable; info = index of upvalue in 'upvalues' */
-  VCONST,  /* compile-time constant; info = absolute index in 'actvar.arr'  */
+  VCONST,  /* compile-time <const> variable;
+              info = absolute index in 'actvar.arr'  */
   VINDEXED,  /* indexed variable;
                 ind.t = table register;
                 ind.idx = key's R index */
diff --git a/3rd/lua/ltable.c b/3rd/lua/ltable.c
index ecfd595a..b3840e77 100644
--- a/3rd/lua/ltable.c
+++ b/3rd/lua/ltable.c
@@ -166,17 +166,24 @@ static Node *mainpositionTV (const Table *t, const TValue *key) {
 
 
 /*
-** Check whether key 'k1' is equal to the key in node 'n2'.
-** This equality is raw, so there are no metamethods. Floats
-** with integer values have been normalized, so integers cannot
-** be equal to floats. It is assumed that 'eqshrstr' is simply
-** pointer equality, so that short strings are handled in the
-** default case.
+** Check whether key 'k1' is equal to the key in node 'n2'. This
+** equality is raw, so there are no metamethods. Floats with integer
+** values have been normalized, so integers cannot be equal to
+** floats. It is assumed that 'eqshrstr' is simply pointer equality, so
+** that short strings are handled in the default case.
 ** A true 'deadok' means to accept dead keys as equal to their original
-** values, which can only happen if the original key was collectable.
-** All dead values are compared in the default case, by pointer
-** identity.  (Note that dead long strings are also compared by
-** identity).
+** values. All dead keys are compared in the default case, by pointer
+** identity. (Only collectable objects can produce dead keys.) Note that
+** dead long strings are also compared by identity.
+** Once a key is dead, its corresponding value may be collected, and
+** then another value can be created with the same address. If this
+** other value is given to 'next', 'equalkey' will signal a false
+** positive. In a regular traversal, this situation should never happen,
+** as all keys given to 'next' came from the table itself, and therefore
+** could not have been collected. Outside a regular traversal, we
+** have garbage in, garbage out. What is relevant is that this false
+** positive does not break anything.  (In particular, 'next' will return
+** some other valid item on the table or nil.)
 */
 static int equalkey (const TValue *k1, const Node *n2, int deadok) {
   if ((rawtt(k1) != keytt(n2)) &&  /* not the same variants? */
diff --git a/3rd/lua/lua.c b/3rd/lua/lua.c
index 454ce12f..b5b884b6 100644
--- a/3rd/lua/lua.c
+++ b/3rd/lua/lua.c
@@ -416,14 +416,18 @@ static int handle_luainit (lua_State *L) {
 
 
 /*
-** Returns the string to be used as a prompt by the interpreter.
+** Return the string to be used as a prompt by the interpreter. Leave
+** the string (or nil, if using the default value) on the stack, to keep
+** it anchored.
 */
 static const char *get_prompt (lua_State *L, int firstline) {
-  const char *p;
-  lua_getglobal(L, firstline ? "_PROMPT" : "_PROMPT2");
-  p = lua_tostring(L, -1);
-  if (p == NULL) p = (firstline ? LUA_PROMPT : LUA_PROMPT2);
-  return p;
+  if (lua_getglobal(L, firstline ? "_PROMPT" : "_PROMPT2") == LUA_TNIL)
+    return (firstline ? LUA_PROMPT : LUA_PROMPT2);  /* use the default */
+  else {  /* apply 'tostring' over the value */
+    const char *p = luaL_tolstring(L, -1, NULL);
+    lua_remove(L, -2);  /* remove original value */
+    return p;
+  }
 }
 
 /* mark in error messages for incomplete statements */
diff --git a/3rd/lua/lvm.c b/3rd/lua/lvm.c
index 24cc8155..e6e1033a 100644
--- a/3rd/lua/lvm.c
+++ b/3rd/lua/lvm.c
@@ -1094,15 +1094,11 @@ void luaV_finishOp (lua_State *L) {
 #define ProtectNT(exp)  (savepc(L), (exp), updatetrap(ci))
 
 /*
-** Protect code that will finish the loop (returns) or can only raise
-** errors. (That is, it will not return to the interpreter main loop
-** after changing the stack or hooks.)
+** Protect code that can only raise errors. (That is, it cannnot change
+** the stack or hooks.)
 */
 #define halfProtect(exp)  (savestate(L,ci), (exp))
 
-/* idem, but without changing the stack */
-#define halfProtectNT(exp)  (savepc(L), (exp))
-
 /* 'c' is the limit of live values in the stack */
 #define checkGC(L,c)  \
 	{ luaC_condGC(L, (savepc(L), L->top = (c)), \
@@ -1134,17 +1130,20 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
 #if LUA_USE_JUMPTABLE
 #include "ljumptab.h"
 #endif
- execute:
+ startfunc:
   trap = L->hookmask;
+ returning:  /* trap already set */
   cl = clLvalue(s2v(ci->func));
   k = cl->p->k;
   pc = ci->u.l.savedpc;
   if (trap) {
-    if (cl->p->is_vararg)
-      trap = 0;  /* hooks will start after VARARGPREP instruction */
-    else if (pc == cl->p->code)  /* first instruction (not resuming)? */
-      luaD_hookcall(L, ci);
-    ci->u.l.trap = 1;  /* there may be other hooks */
+    if (pc == cl->p->code) {  /* first instruction (not resuming)? */
+      if (cl->p->is_vararg)
+        trap = 0;  /* hooks will start after VARARGPREP instruction */
+      else  /* check 'call' hook */
+        luaD_hookcall(L, ci);
+    }
+    ci->u.l.trap = 1;  /* assume trap is on, for now */
   }
   base = ci->func + 1;
   /* main loop of interpreter */
@@ -1617,10 +1616,10 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         savepc(L);  /* in case of errors */
         if ((newci = luaD_precall(L, ra, nresults)) == NULL)
           updatetrap(ci);  /* C call; nothing else to be done */
-        else {  /* Lua call: run function in this same invocation */
+        else {  /* Lua call: run function in this same C frame */
           ci = newci;
           ci->callstatus = 0;  /* call re-uses 'luaV_execute' */
-          goto execute;
+          goto startfunc;
         }
         vmbreak;
       }
@@ -1633,7 +1632,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
           L->top = ra + b;
         else  /* previous instruction set top */
           b = cast_int(L->top - ra);
-        savepc(ci);  /* some calls here can raise errors */
+        savepc(ci);  /* several calls here can raise errors */
         if (TESTARG_k(i)) {
           /* close upvalues from current call; the compiler ensures
              that there are no to-be-closed variables here, so this
@@ -1652,11 +1651,12 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
           updatestack(ci);  /* stack may have been relocated */
           ci->func -= delta;  /* restore 'func' (if vararg) */
           luaD_poscall(L, ci, cast_int(L->top - ra));  /* finish caller */
+          updatetrap(ci);  /* 'luaD_poscall' can change hooks */
           goto ret;  /* caller returns after the tail call */
         }
         ci->func -= delta;  /* restore 'func' (if vararg) */
         luaD_pretailcall(L, ci, ra, b);  /* prepare call frame */
-        goto execute;  /* execute the callee */
+        goto startfunc;  /* execute the callee */
       }
       vmcase(OP_RETURN) {
         int n = GETARG_B(i) - 1;  /* number of results */
@@ -1675,12 +1675,15 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
           ci->func -= ci->u.l.nextraargs + nparams1;
         L->top = ra + n;  /* set call for 'luaD_poscall' */
         luaD_poscall(L, ci, n);
+        updatetrap(ci);  /* 'luaD_poscall' can change hooks */
         goto ret;
       }
       vmcase(OP_RETURN0) {
         if (L->hookmask) {
           L->top = ra;
-          halfProtectNT(luaD_poscall(L, ci, 0));  /* no hurry... */
+          savepc(ci);
+          luaD_poscall(L, ci, 0);  /* no hurry... */
+          trap = 1;
         }
         else {  /* do the 'poscall' here */
           int nres = ci->nresults;
@@ -1694,7 +1697,9 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
       vmcase(OP_RETURN1) {
         if (L->hookmask) {
           L->top = ra + 1;
-          halfProtectNT(luaD_poscall(L, ci, 1));  /* no hurry... */
+          savepc(ci);
+          luaD_poscall(L, ci, 1);  /* no hurry... */
+          trap = 1;
         }
         else {  /* do the 'poscall' here */
           int nres = ci->nresults;
@@ -1708,12 +1713,12 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
               setnilvalue(s2v(L->top++));
           }
         }
-       ret:
+       ret:  /* return from a Lua function */
         if (ci->callstatus & CIST_FRESH)
           return;  /* end this frame */
         else {
           ci = ci->previous;
-          goto execute;  /* continue running caller in this frame */
+          goto returning;  /* continue running caller in this frame */
         }
       }
       vmcase(OP_FORLOOP) {