Fix a number of cases in the parser where segfaults were possible with malformed programs.

parse.yy

@@ -305,10 +305,14 @@ cast_expression
           // uniform float x = 1. / (float)y;
           // don't issue an error due to (float)y being inadvertently
           // and undesirably-to-the-user "varying"...
+          if ($2 == NULL || $4 == NULL || $4->GetType() == NULL)
+              $$ = NULL;
+          else {
               if ($4->GetType()->IsUniformType())
                  $2 = $2->GetAsUniformType();
               $$ = new TypeCastExpr($2, $4, @1); 
           }
+      }
     ;
 
 multiplicative_expression
@@ -459,6 +463,7 @@ declaration_specifiers
     | storage_class_specifier declaration_specifiers
       {
           DeclSpecs *ds = (DeclSpecs *)$2;
+          if (ds != NULL) {
               if (ds->storageClass != SC_NONE)
                   Error(@1, "Multiple storage class specifiers in a declaration are illegal. "
                         "(Have provided both \"%s\" and \"%s\".)",
@@ -466,6 +471,7 @@ declaration_specifiers
                         lGetStorageClassString($1));
               else
                   ds->storageClass = $1;
+          }
           $$ = ds;
       }
     | soa_width_specifier
@@ -477,10 +483,12 @@ declaration_specifiers
     | soa_width_specifier declaration_specifiers
       {
           DeclSpecs *ds = (DeclSpecs *)$2;
+          if (ds != NULL) {
               if (ds->soaWidth != 0)
                   Error(@1, "soa<> qualifier supplied multiple times in declaration.");
               else
                   ds->soaWidth = $1;
+          }
           $$ = ds;
       }
     | type_specifier
@@ -496,9 +504,11 @@ declaration_specifiers
     | type_specifier declaration_specifiers
       {
           DeclSpecs *ds = (DeclSpecs *)$2;
+          if (ds != NULL) {
               if (ds->baseType != NULL)
                   Error(@1, "Multiple types provided for declaration.");
               ds->baseType = $1;
+          }
           $$ = ds;
       }
     | type_qualifier
@@ -508,6 +518,7 @@ declaration_specifiers
     | type_qualifier declaration_specifiers
       {
           DeclSpecs *ds = (DeclSpecs *)$2;
+          if (ds != NULL)
               ds->typeQualifier |= $1;
           $$ = ds;
       }
@@ -523,6 +534,7 @@ init_declarator_list
     | init_declarator_list ',' init_declarator
       {
           std::vector<Declarator *> *dl = (std::vector<Declarator *> *)$1;
+          if (dl != NULL && $3 != NULL)
               dl->push_back($3);
           $$ = $1;
       }
@@ -530,7 +542,12 @@ init_declarator_list
 
 init_declarator
     : declarator
-    | declarator '=' initializer { $1->initExpr = $3; $$ = $1; }
+    | declarator '=' initializer 
+      {
+          if ($1 != NULL)
+              $1->initExpr = $3; 
+          $$ = $1; 
+      }
     ;
 
 storage_class_specifier
@@ -637,12 +654,14 @@ struct_declaration_list
     : struct_declaration 
       { 
           std::vector<StructDeclaration *> *sdl = new std::vector<StructDeclaration *>;
+          if (sdl != NULL && $1 != NULL)
               sdl->push_back($1);
           $$ = sdl;
       }
     | struct_declaration_list struct_declaration 
       {
           std::vector<StructDeclaration *> *sdl = (std::vector<StructDeclaration *> *)$1;
+          if (sdl != NULL && $2 != NULL)
               sdl->push_back($2);
           $$ = $1;
       }
@@ -659,6 +678,7 @@ specifier_qualifier_list
     | short_vec_specifier
     | type_qualifier specifier_qualifier_list 
     {
+        if ($2 != NULL) {
             if ($1 == TYPEQUAL_UNIFORM)
                 $$ = $2->GetAsUniformType();
             else if ($1 == TYPEQUAL_VARYING)
@@ -681,6 +701,9 @@ specifier_qualifier_list
                 UNIMPLEMENTED;
             }
         }
+        else
+            $$ = NULL;
+    }
 /* K&R--implicit int type--e.g. "static foo" -> foo is an int */
 /*    | type_qualifier { UNIMPLEMENTED; }*/
     ;
@@ -690,12 +713,14 @@ struct_declarator_list
     : struct_declarator 
       {
           std::vector<Declarator *> *sdl = new std::vector<Declarator *>;
+          if ($1 != NULL)
               sdl->push_back($1);
           $$ = sdl;
       }
     | struct_declarator_list ',' struct_declarator 
       {
           std::vector<Declarator *> *sdl = (std::vector<Declarator *> *)$1;
+          if (sdl != NULL && $3 != NULL)
               sdl->push_back($3);
           $$ = $1;
       }
@@ -757,8 +782,9 @@ direct_declarator
     | direct_declarator '[' constant_expression ']'
     {
         Expr *size = $3;
-        if (size) size = size->TypeCheck();
+        if (size)
-        if (size) {
+            size = size->TypeCheck();
+        if (size && $1 != NULL) {
             size = size->Optimize();
             llvm::Constant *cval = size->GetConstant(size->GetType());
             if (!cval) {
@@ -780,20 +806,24 @@ direct_declarator
     }
     | direct_declarator '[' ']'
     {
+        if ($1 != NULL)
             $1->AddArrayDimension(-1); // unsized
         $$ = $1;
     }
     | direct_declarator '(' parameter_type_list ')'
       {
           Declarator *d = (Declarator *)$1;
+          if (d != NULL) {
               d->isFunction = true;
               d->functionArgs = $3;
+          }
           $$ = d;
       }
 /* K&R?   | direct_declarator '(' identifier_list ')' */
     | direct_declarator '(' ')'
       {
           Declarator *d = (Declarator *)$1;
+          if (d != NULL)
               d->isFunction = true;
           $$ = d;
       }
@@ -844,6 +874,7 @@ parameter_declaration
     }
     | declaration_specifiers declarator '=' initializer
     { 
+        if ($2 != NULL)
             $2->initExpr = $4;
         $$ = new Declaration($1, $2); 
 
@@ -900,11 +931,15 @@ initializer_list
       { $$ = new ExprList($1, @1); }
     | initializer_list ',' initializer
       {
+          if ($1 == NULL)
+              $$ = NULL;
+          else {
               ExprList *exprList = dynamic_cast<ExprList *>($1);
               assert(exprList);
               exprList->exprs.push_back($3);
               $$ = exprList;
           }
+      }
     ;
 
 statement
@@ -960,6 +995,7 @@ statement_list
       }
     | statement_list statement
       {
+          if ($1 != NULL)
               ((StmtList *)$1)->Add($2);
           $$ = $1;
       }
@@ -1084,6 +1120,7 @@ external_declaration
     | TOKEN_EXTERN TOKEN_STRING_LITERAL '{' declaration '}' // FIXME: make sure string=="C"
     | declaration 
     { 
+        if ($1 != NULL)
             for (unsigned int i = 0; i < $1->declarators.size(); ++i)
                 m->AddGlobal($1->declSpecs, $1->declarators[i]);
     }
@@ -1127,6 +1164,8 @@ lAddFunctionParams(Declarator *decl) {
     if (decl->functionArgs) {
         for (unsigned int i = 0; i < decl->functionArgs->size(); ++i) {
             Declaration *pdecl = (*decl->functionArgs)[i];
+            if (pdecl == NULL)
+                continue;
             assert(pdecl->declarators.size() == 1);
             Symbol *sym = pdecl->declarators[0]->sym;
 #ifndef NDEBUG