Internalized string "break" kept by the parser

The parser uses "break" as fake label to compile "break" as "goto
break". To avoid producing this string at each use, it keeps it
available in its state.

llex.c

@@ -190,6 +190,9 @@ void luaX_setinput (lua_State *L, LexState *ls, ZIO *z, TString *source,
   ls->lastline = 1;
   ls->source = source;
   ls->envn = luaS_newliteral(L, LUA_ENV);  /* get env name */
+  ls->brkn = luaS_newliteral(L, "break");  /* get "break" name */
+  /* "break" cannot be collected, as it is a reserved word" */
+  lua_assert(isreserved(ls->brkn));
   luaZ_resizebuffer(ls->L, ls->buff, LUA_MINBUFFER);  /* initialize buffer */
 }
 

llex.h

@@ -75,6 +75,7 @@ typedef struct LexState {
   struct Dyndata *dyd;  /* dynamic structures used by the parser */
   TString *source;  /* current source name */
   TString *envn;  /* environment variable name */
+  TString *brkn;  /* "break" name (used as a label) */
 } LexState;
 
 

lparser.c

@@ -707,7 +707,7 @@ static void enterblock (FuncState *fs, BlockCnt *bl, lu_byte isloop) {
 */
 static l_noret undefgoto (LexState *ls, Labeldesc *gt) {
   /* breaks are checked when created, cannot be undefined */
-  lua_assert(!eqstr(gt->name, luaS_newliteral(ls->L, "break")));
+  lua_assert(!eqstr(gt->name, ls->brkn));
   luaK_semerror(ls, "no visible label '%s' for <goto> at line %d",
                     getstr(gt->name), gt->line);
 }
@@ -723,7 +723,7 @@ static void leaveblock (FuncState *fs) {
   removevars(fs, bl->nactvar);  /* remove block locals */
   lua_assert(bl->nactvar == fs->nactvar);  /* back to level on entry */
   if (bl->isloop == 2)  /* has to fix pending breaks? */
-    createlabel(ls, luaS_newliteral(ls->L, "break"), 0, 0);
+    createlabel(ls, ls->brkn, 0, 0);
   solvegotos(fs, bl);
   if (bl->previous == NULL) {  /* was it the last block? */
     if (bl->firstgoto < ls->dyd->gt.n)  /* still pending gotos? */
@@ -1497,7 +1497,7 @@ static void breakstat (LexState *ls, int line) {
  ok:
   bl->isloop = 2;  /* signal that block has pending breaks */
   luaX_next(ls);  /* skip break */
-  newgotoentry(ls, luaS_newliteral(ls->L, "break"), line);
+  newgotoentry(ls, ls->brkn, line);
 }