Here are some fixes to lemon.c:

• consistently check for allocation errors
• remove unnecessary memset after calloc
• remove superfluous returns from void functions
• State_new checks for NULL so remove MemoryCheck

Index: tool/lemon.c
==================================================================
--- tool/lemon.c
+++ tool/lemon.c
@@ -623,11 +623,10 @@
   acttab *p = (acttab *) calloc( 1, sizeof(*p) );
   if( p==0 ){
     fprintf(stderr,"Unable to allocate memory for a new acttab.");
     exit(1);
   }
-  memset(p, 0, sizeof(*p));
   p->nsymbol = nsymbol;
   p->nterminal = nterminal;
   return p;
 }
 
@@ -826,11 +825,10 @@
           rp->precsym = rp->rhs[i];
         }
       }
     }
   }
-  return;
 }
 
 /* Find all nonterminals which will generate the empty string.
 ** Then go back and compute the first sets of every nonterminal.
 ** The first set is the set of all terminal symbols which can begin
@@ -889,11 +887,10 @@
           if( s2->lambda==LEMON_FALSE ) break;
         }
       }
     }
   }while( progress );
-  return;
 }
 
 /* Compute all LR(0) states for the grammar.  Links
 ** are added to between some states so that the LR(1) follow sets
 ** can be computed later.
@@ -949,11 +946,10 @@
 
   /* Compute the first state.  All other states will be
   ** computed automatically during the computation of the first one.
   ** The returned pointer to the first state is not used. */
   (void)getstate(lemp);
-  return;
 }
 
 /* Return a pointer to a state which is described by the configuration
 ** list which has been built from calls to Configlist_add.
 */
@@ -986,11 +982,10 @@
     /* This really is a new state.  Construct all the details */
     Configlist_closure(lemp);    /* Compute the configuration closure */
     Configlist_sort();           /* Sort the configuration closure */
     cfp = Configlist_return();   /* Get a pointer to the config list */
     stp = State_new();           /* A new state structure */
-    MemoryCheck(stp);
     stp->bp = bp;                /* Remember the configuration basis */
     stp->cfp = cfp;              /* Remember the configuration closure */
     stp->statenum = lemp->nstate++; /* Every state gets a sequence number */
     stp->ap = 0;                 /* No actions, yet. */
     State_insert(stp,stp->bp);   /* Add to the state table */
@@ -1328,21 +1323,19 @@
   current = 0;
   currentend = &current;
   basis = 0;
   basisend = &basis;
   Configtable_init();
-  return;
 }
 
 /* Initialized the configuration list builder */
 void Configlist_reset(void){
   current = 0;
   currentend = &current;
   basis = 0;
   basisend = &basis;
   Configtable_clear(0);
-  return;
 }
 
 /* Add another configuration to the configuration list */
 struct config *Configlist_add(
   struct rule *rp,    /* The rule */
@@ -1438,27 +1431,24 @@
         }
         if( i==rp->nrhs ) Plink_add(&cfp->fplp,newcfp);
       }
     }
   }
-  return;
 }
 
 /* Sort the configuration list */
 void Configlist_sort(void){
   current = (struct config*)msort((char*)current,(char**)&(current->next),
                                   Configcmp);
   currentend = 0;
-  return;
 }
 
 /* Sort the basis configuration list */
 void Configlist_sortbasis(void){
   basis = (struct config*)msort((char*)current,(char**)&(current->bp),
                                 Configcmp);
   basisend = 0;
-  return;
 }
 
 /* Return a pointer to the head of the configuration list and
 ** reset the list */
 struct config *Configlist_return(void){
@@ -1488,11 +1478,10 @@
     assert( cfp->fplp==0 );
     assert( cfp->bplp==0 );
     if( cfp->fws ) SetFree(cfp->fws);
     deleteconfig(cfp);
   }
-  return;
 }
 /***************** From the file "error.c" *********************************/
 /*
 ** Code for printing error message.
 */
@@ -2429,21 +2418,32 @@
       }else if( (x[0]=='|' || x[0]=='/') && psp->nrhs>0 && ISUPPER(x[1]) ){
         struct symbol *msp = psp->rhs[psp->nrhs-1];
         if( msp->type!=MULTITERMINAL ){
           struct symbol *origsp = msp;
           msp = (struct symbol *) calloc(1,sizeof(*msp));
-          memset(msp, 0, sizeof(*msp));
+          if( msp==0 ){
+            fprintf(stderr,"malloc failed\n");
+            exit(1);
+          }
           msp->type = MULTITERMINAL;
           msp->nsubsym = 1;
           msp->subsym = (struct symbol **) calloc(1,sizeof(struct symbol*));
+          if( msp->subsym==0 ){
+            fprintf(stderr,"malloc failed\n");
+            exit(1);
+          }
           msp->subsym[0] = origsp;
           msp->name = origsp->name;
           psp->rhs[psp->nrhs-1] = msp;
         }
         msp->nsubsym++;
         msp->subsym = (struct symbol **) realloc(msp->subsym,
           sizeof(struct symbol*)*msp->nsubsym);
+        if( msp->subsym==0 ){
+          fprintf(stderr,"malloc failed\n");
+          exit(1);
+        }
         msp->subsym[msp->nsubsym-1] = Symbol_new(&x[1]);
         if( ISLOWER(x[1]) || ISLOWER(msp->subsym[0]->name[0]) ){
           ErrorMsg(psp->filename,psp->tokenlineno,
             "Cannot form a compound containing a non-terminal");
           psp->errorcnt++;
@@ -2764,10 +2764,14 @@
       }else if( ISUPPER(x[0]) || ((x[0]=='|' || x[0]=='/') && ISUPPER(x[1])) ){
         struct symbol *msp = psp->tkclass;
         msp->nsubsym++;
         msp->subsym = (struct symbol **) realloc(msp->subsym,
           sizeof(struct symbol*)*msp->nsubsym);
+        if( msp->subsym==0 ){
+          fprintf(stderr,"malloc failed\n");
+          exit(1);
+        }
         if( !ISUPPER(x[0]) ) x++;
         msp->subsym[msp->nsubsym-1] = Symbol_new(x);
       }else{
         ErrorMsg(psp->filename, psp->tokenlineno,
           "%%token_class argument \"%s\" should be a token", x);
@@ -2957,11 +2961,11 @@
   int lineno;
   int c;
   char *cp, *nextcp;
   int startline = 0;
 
-  memset(&ps, '\0', sizeof(ps));
+  memset(&ps, 0, sizeof(ps));
   ps.gp = gp;
   ps.filename = gp->filename;
   ps.errorcnt = 0;
   ps.state = INITIALIZE;
 
@@ -2974,10 +2978,14 @@
   }
   fseek(fp,0,2);
   filesize = ftell(fp);
   rewind(fp);
   filebuf = (char *)malloc( filesize+1 );
+  if( filebuf==0 ){
+    fprintf(stderr,"malloc failed\n");
+    exit(1);
+  }
   if( filesize>100000000 || filebuf==0 ){
     ErrorMsg(ps.filename,0,"Input file too large.");
     free(filebuf);
     gp->errorcnt++;
     fclose(fp);
@@ -3507,11 +3515,10 @@
               rp->precsym->name, rp->precsym->prec);
     }
     fprintf(fp,"\n");
   }
   fclose(fp);
-  return;
 }
 
 /* Search for the file "name" which is in the same directory as
 ** the executable */
 PRIVATE char *pathsearch(char *argv0, char *name, int modemask)
@@ -3712,11 +3719,10 @@
     (*lineno)++;
   }
   if (!lemp->nolinenosflag) {
     (*lineno)++; tplt_linedir(out,*lineno,lemp->outname);
   }
-  return;
 }
 
 /*
 ** The following routine emits code for the destructor for the
 ** symbol sp
@@ -3759,11 +3765,10 @@
  fprintf(out,"\n"); (*lineno)++;
  if (!lemp->nolinenosflag) {
    (*lineno)++; tplt_linedir(out,*lineno,lemp->outname);
  }
  fprintf(out,"}\n"); (*lineno)++;
- return;
 }
 
 /*
 ** Return TRUE (non-zero) if the given symbol has a destructor.
 */
@@ -4071,12 +4076,10 @@
  }
 
  if( rp->codePrefix ){
    fprintf(out, "}\n"); (*lineno)++;
  }
-
- return;
 }
 
 /*
 ** Print the definition of the union used for the parser's data stack.
 ** This union contains fields for every possible data type for tokens
@@ -4934,11 +4937,10 @@
 
   acttab_free(pActtab);
   fclose(in);
   fclose(out);
   if( sql ) fclose(sql);
-  return;
 }
 
 /* Generate a header file for the parser */
 void ReportHeader(struct lemon *lemp)
 {
@@ -4970,11 +4972,10 @@
     for(i=1; i<lemp->nterminal; i++){
       fprintf(out,"#define %s%-30s %3d\n",prefix,lemp->symbols[i]->name,i);
     }
     fclose(out);
   }
-  return;
 }
 
 /* Reduce the size of the action tables, if possible, by making use
 ** of defaults.
 **
@@ -5879,7 +5880,6 @@
   int i;
   if( x4a==0 || x4a->count==0 ) return;
   if( f ) for(i=0; i<x4a->count; i++) (*f)(x4a->tbl[i].data);
   for(i=0; i<x4a->size; i++) x4a->ht[i] = 0;
   x4a->count = 0;
-  return;
 }