Making yyGLRStackItem know its type

[Akim Demaille]

In the process of trying to harness glr.c into a glr.cc, I found that
the union

union yyGLRStackItem {
  yyGLRState yystate;
  yySemanticOption yyoption;
};

with both cases starting by a Boolean was a bit troublesome.  I do
understand that this allows shorter and simpler names, simple
assignments, but it is a bit unusual (to my eyes).  Could it be also
to optimize in some way to size of the union?

So I would like to move to using a more traditional

struct yyGLRStackItem {
  yybool yyisState;
  union {
    yyGLRState yystate;
    yySemanticOption yyoption;
  } u;
};

but to this end, I first wanted to clean up the allocations.  Ok to
install?

And what about changing yyGLRStackItem as suggested above?


Index: ChangeLog
from  Akim Demaille  <address@hidden>

        * data/glr.c (yynewGLRStackItem, YY_RESERVE_GLRSTACK): New.
        (yyaddDeferredAction, yyglrShift, yyglrShiftDefer): Use them.
        (yyexpandGLRStack, YYRELOC): Define only when YYSTACKEXPANDABLE.

Index: data/glr.c
===================================================================
RCS file: /cvsroot/bison/bison/data/glr.c,v
retrieving revision 1.131
diff -u -u -r1.131 glr.c
--- data/glr.c 31 Oct 2005 01:16:32 -0000 1.131
+++ data/glr.c 10 Nov 2005 15:14:04 -0000
@@ -591,6 +591,21 @@
 # endif
 #endif
 
+#if YYSTACKEXPANDABLE
+# define YY_RESERVE_GLRSTACK(Yystack)                  \
+  do {                                                 \
+    if (Yystack->yyspaceLeft < YYHEADROOM)             \
+      yyexpandGLRStack (Yystack);                      \
+  } while (/*CONSTCOND*/ 0)
+#else
+# define YY_RESERVE_GLRSTACK(Yystack)                  \
+  do {                                                 \
+    if (Yystack->yyspaceLeft < YYHEADROOM)             \
+      yyMemoryExhausted (Yystack);
+  } while (/*CONSTCOND*/ 0)
+#endif
+
+
 #if YYERROR_VERBOSE
 
 # ifndef yystpcpy
@@ -1020,21 +1035,32 @@
 
                                /* GLRStates */
 
+/** Return a fresh GLRStackItem.  Callers should call
+ * YY_RESERVE_GLRSTACK afterwards to make sure there is sufficient
+ * headroom.  */
+
+static inline yyGLRStackItem*
+yynewGLRStackItem (yyGLRStack* yystack, yybool yyisState)
+{
+  yyGLRStackItem* yynewItem = yystack->yynextFree;
+  yystack->yyspaceLeft -= 1;
+  yystack->yynextFree += 1;
+  yynewItem->yystate.yyisState = yyisState;
+  return yynewItem;
+}
+
 static void
 yyaddDeferredAction (yyGLRStack* yystack, yyGLRState* yystate,
                     yyGLRState* rhs, yyRuleNum yyrule)
 {
-  yySemanticOption* yynewItem;
-  yynewItem = &yystack->yynextFree->yyoption;
-  yystack->yyspaceLeft -= 1;
-  yystack->yynextFree += 1;
-  yynewItem->yyisState = yyfalse;
-  yynewItem->yystate = rhs;
-  yynewItem->yyrule = yyrule;
-  yynewItem->yynext = yystate->yysemantics.yyfirstVal;
-  yystate->yysemantics.yyfirstVal = yynewItem;
-  if (yystack->yyspaceLeft < YYHEADROOM)
-    yyexpandGLRStack (yystack);
+  yySemanticOption* yynewOption =
+    &yynewGLRStackItem (yystack, yyfalse)->yyoption;
+  yynewOption->yystate = rhs;
+  yynewOption->yyrule = yyrule;
+  yynewOption->yynext = yystate->yysemantics.yyfirstVal;
+  yystate->yysemantics.yyfirstVal = yynewOption;
+
+  YY_RESERVE_GLRSTACK (yystack);
 }
 
                                /* GLRStacks */
@@ -1075,7 +1101,9 @@
   return yyinitStateSet (&yystack->yytops);
 }
 
-#define YYRELOC(YYFROMITEMS,YYTOITEMS,YYX,YYTYPE) \
+
+#if YYSTACKEXPANDABLE
+# define YYRELOC(YYFROMITEMS,YYTOITEMS,YYX,YYTYPE) \
   &((YYTOITEMS) - ((YYFROMITEMS) - (yyGLRStackItem*) (YYX)))->YYTYPE
 
 /** If STACK is expandable, extend it.  WARNING: Pointers into the
@@ -1086,7 +1114,6 @@
 static void
 yyexpandGLRStack (yyGLRStack* yystack)
 {
-#if YYSTACKEXPANDABLE
   yyGLRStackItem* yynewItems;
   yyGLRStackItem* yyp0, *yyp1;
   size_t yysize, yynewSize;
@@ -1139,11 +1166,8 @@
   yystack->yyitems = yynewItems;
   yystack->yynextFree = yynewItems + yysize;
   yystack->yyspaceLeft = yynewSize - yysize;
-
-#else
-  yyMemoryExhausted (yystack);
-#endif
 }
+#endif
 
 static void
 yyfreeGLRStack (yyGLRStack* yystack)
@@ -1221,21 +1245,17 @@
            size_t yyposn,
            YYSTYPE yysval, YYLTYPE* yylocp)
 {
-  yyGLRStackItem* yynewItem;
+  yyGLRState* yynewState = &yynewGLRStackItem (yystack, yytrue)->yystate;
 
-  yynewItem = yystack->yynextFree;
-  yystack->yynextFree += 1;
-  yystack->yyspaceLeft -= 1;
-  yynewItem->yystate.yyisState = yytrue;
-  yynewItem->yystate.yylrState = yylrState;
-  yynewItem->yystate.yyposn = yyposn;
-  yynewItem->yystate.yyresolved = yytrue;
-  yynewItem->yystate.yypred = yystack->yytops.yystates[yyk];
-  yystack->yytops.yystates[yyk] = &yynewItem->yystate;
-  yynewItem->yystate.yysemantics.yysval = yysval;
-  yynewItem->yystate.yyloc = *yylocp;
-  if (yystack->yyspaceLeft < YYHEADROOM)
-    yyexpandGLRStack (yystack);
+  yynewState->yylrState = yylrState;
+  yynewState->yyposn = yyposn;
+  yynewState->yyresolved = yytrue;
+  yynewState->yypred = yystack->yytops.yystates[yyk];
+  yynewState->yysemantics.yysval = yysval;
+  yynewState->yyloc = *yylocp;
+  yystack->yytops.yystates[yyk] = yynewState;
+
+  YY_RESERVE_GLRSTACK (yystack);
 }
 
 /** Shift stack #K of YYSTACK, to a new state corresponding to LR
@@ -1245,19 +1265,17 @@
 yyglrShiftDefer (yyGLRStack* yystack, size_t yyk, yyStateNum yylrState,
                 size_t yyposn, yyGLRState* rhs, yyRuleNum yyrule)
 {
-  yyGLRStackItem* yynewItem;
+  yyGLRState* yynewState = &yynewGLRStackItem (yystack, yytrue)->yystate;
 
-  yynewItem = yystack->yynextFree;
-  yynewItem->yystate.yyisState = yytrue;
-  yynewItem->yystate.yylrState = yylrState;
-  yynewItem->yystate.yyposn = yyposn;
-  yynewItem->yystate.yyresolved = yyfalse;
-  yynewItem->yystate.yypred = yystack->yytops.yystates[yyk];
-  yynewItem->yystate.yysemantics.yyfirstVal = NULL;
-  yystack->yytops.yystates[yyk] = &yynewItem->yystate;
-  yystack->yynextFree += 1;
-  yystack->yyspaceLeft -= 1;
-  yyaddDeferredAction (yystack, &yynewItem->yystate, rhs, yyrule);
+  yynewState->yylrState = yylrState;
+  yynewState->yyposn = yyposn;
+  yynewState->yyresolved = yyfalse;
+  yynewState->yypred = yystack->yytops.yystates[yyk];
+  yynewState->yysemantics.yyfirstVal = NULL;
+  yystack->yytops.yystates[yyk] = yynewState;
+
+  /* Invokes YY_RESERVE_GLRSTACK. */
+  yyaddDeferredAction (yystack, yynewState, rhs, yyrule);
 }
 
 /** Pop the symbols consumed by reduction #RULE from the top of stack