Fix for br991 - compiler crashes due to null statements.

The reported problem was caused by a null statement in a case statement,
which caused the check for an infinite loop to fail. Further testing
exposed more problems with null statements in loop statements - these
caused crashes earlier in elaboration.

elaborate.cc

@@ -4039,9 +4039,18 @@ NetProc* PDisable::elaborate(Design*des, NetScope*scope) const
  */
 NetProc* PDoWhile::elaborate(Design*des, NetScope*scope) const
 {
-      NetExpr*tmp = elab_and_eval(des, scope, cond_, -1);
+      NetExpr*ce = elab_and_eval(des, scope, cond_, -1);
-      tmp->set_line(*this);
+      NetProc*sub;
-      NetDoWhile*loop = new NetDoWhile(tmp, statement_->elaborate(des, scope));
+      if (statement_)
+	    sub = statement_->elaborate(des, scope);
+      else
+	    sub = new NetBlock(NetBlock::SEQU, 0);
+      if (ce == 0 || sub == 0) {
+	    delete ce;
+	    delete sub;
+	    return 0;
+      }
+      NetDoWhile*loop = new NetDoWhile(ce, sub);
       loop->set_line(*this);
       return loop;
 }
@@ -4572,7 +4581,11 @@ NetProc* PEventStatement::elaborate(Design*des, NetScope*scope) const
  */
 NetProc* PForever::elaborate(Design*des, NetScope*scope) const
 {
-      NetProc*stat = statement_->elaborate(des, scope);
+      NetProc*stat;
+      if (statement_)
+	    stat = statement_->elaborate(des, scope);
+      else
+	    stat = new NetBlock(NetBlock::SEQU, 0);
       if (stat == 0) return 0;
 
       NetForever*proc = new NetForever(stat);
@@ -4778,7 +4791,11 @@ NetProc* PForeach::elaborate(Design*des, NetScope*scope) const
 
 	/* Elaborate the statement that is contained in the foreach
 	   loop. */
-      NetProc*sub = statement_->elaborate(des, scope);
+      NetProc*sub;
+      if (statement_)
+	    sub = statement_->elaborate(des, scope);
+      else
+	    sub = new NetBlock(NetBlock::SEQU, 0);
 
 	/* Make a step statement: idx += 1 */
       NetAssign_*idx_lv = new NetAssign_(idx_sig);
@@ -4809,7 +4826,11 @@ NetProc* PForeach::elaborate_static_array_(Design*des, NetScope*scope,
       ivl_assert(*this, index_vars_.size() > 0);
       ivl_assert(*this, dims.size() == index_vars_.size());
 
-      NetProc*sub = statement_->elaborate(des, scope);
+      NetProc*sub;
+      if (statement_)
+	    sub = statement_->elaborate(des, scope);
+      else
+	    sub = new NetBlock(NetBlock::SEQU, 0);
       NetForLoop*stmt = 0;
 
       for (int idx_idx = index_vars_.size()-1 ; idx_idx >= 0 ; idx_idx -= 1) {
@@ -4903,7 +4924,11 @@ NetProc* PForStatement::elaborate(Design*des, NetScope*scope) const
 	   loop. If there is an error, this will return 0 and I should
 	   skip the append. No need to worry, the error has been
 	   reported so it's OK that the netlist is bogus. */
-      NetProc*sub = statement_->elaborate(des, scope);
+      NetProc*sub;
+      if (statement_)
+	    sub = statement_->elaborate(des, scope);
+      else
+	    sub = new NetBlock(NetBlock::SEQU, 0);
 
 	/* Now elaborate the for_step statement. I really should do
 	   some error checking here to make sure the step statement
@@ -5025,7 +5050,11 @@ NetProc* PRepeat::elaborate(Design*des, NetScope*scope) const
       if (expr->expr_type() == IVL_VT_REAL)
 	    expr = cast_to_int4(expr, 64);
 
-      NetProc*stat = statement_->elaborate(des, scope);
+      NetProc*stat;
+      if (statement_)
+	    stat = statement_->elaborate(des, scope);
+      else
+	    stat = new NetBlock(NetBlock::SEQU, 0);
       if (stat == 0) return 0;
 
 	// If the expression is a constant, handle certain special
@@ -5205,7 +5234,11 @@ NetProc* PTrigger::elaborate(Design*des, NetScope*scope) const
 NetProc* PWhile::elaborate(Design*des, NetScope*scope) const
 {
       NetExpr*ce = elab_and_eval(des, scope, cond_, -1);
-      NetProc*sub = statement_->elaborate(des, scope);
+      NetProc*sub;
+      if (statement_)
+	    sub = statement_->elaborate(des, scope);
+      else
+	    sub = new NetBlock(NetBlock::SEQU, 0);
       if (ce == 0 || sub == 0) {
 	    delete ce;
 	    delete sub;

netlist.cc

@@ -2743,10 +2743,11 @@ DelayType NetCase::delay_type() const
 
       for (unsigned idx = 0; idx < nstmts; idx += 1) {
 	    if (!expr(idx)) def_stmt = true;
+	    DelayType dt = stat(idx) ? stat(idx)->delay_type() : NO_DELAY;
             if (idx == 0) {
-		  result = stat(idx)->delay_type();
+		  result = dt;
             } else {
-		  result = combine_delays(result, stat(idx)->delay_type());
+		  result = combine_delays(result, dt);
             }
       }
 
@@ -2769,6 +2770,7 @@ DelayType NetCondit::delay_type() const
  */
 DelayType NetDoWhile::delay_type() const
 {
+      ivl_assert(*this, proc_);
       return proc_->delay_type();
 }
 
@@ -2779,11 +2781,13 @@ DelayType NetEvWait::delay_type() const
 
 DelayType NetForever::delay_type() const
 {
+      ivl_assert(*this, statement_);
       return statement_->delay_type();
 }
 
 DelayType NetForLoop::delay_type() const
 {
+      ivl_assert(*this, statement_);
       return get_loop_delay_type(condition_, statement_);
 }
 
@@ -2806,6 +2810,7 @@ DelayType NetPDelay::delay_type() const
 
 DelayType NetRepeat::delay_type() const
 {
+      ivl_assert(*this, statement_);
       return get_loop_delay_type(expr_, statement_);
 }
 
@@ -2821,5 +2826,6 @@ DelayType NetUTask::delay_type() const
 
 DelayType NetWhile::delay_type() const
 {
+      ivl_assert(*this, proc_);
       return get_loop_delay_type(cond_, proc_);
 }