From dc203a20ba415ee7bf8c91f6561a2cb5cfa343e8 Mon Sep 17 00:00:00 2001
From: Stephen Williams <steve@icarus.com>
Date: Sat, 23 Apr 2022 18:52:15 -0700
Subject: [PATCH] Handle the error case that the rval fails

There are some cases where the r-value for an assignment just can't
be elaborated. Instead of segfaulting on the error, handle it by
assuming that the nullptr came from an error message, and ignore it
going forward.
---
 design_dump.cc   | 10 ++++++++--
 net_func_eval.cc |  7 +++++--
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/design_dump.cc b/design_dump.cc
index 9fa0ba876..f6540a6da 100644
--- a/design_dump.cc
+++ b/design_dump.cc
@@ -1124,7 +1124,10 @@ void NetAssign::dump(ostream&o, unsigned ind) const
       if (const NetExpr*de = get_delay())
 	    o << "#(" << *de << ") ";
 
-      o << *rval() << ";" << endl;
+      if (rval())
+	    o << *rval() << ";" << endl;
+      else
+	    o << "<rval elaboration error>;" << endl;
 }
 
 void NetAssignNB::dump(ostream&o, unsigned ind) const
@@ -1142,7 +1145,10 @@ void NetAssignNB::dump(ostream&o, unsigned ind) const
 	    o << *event_;
       }
 
-      o << *rval() << ";" << endl;
+      if (rval())
+	    o << *rval() << ";" << endl;
+      else
+	    o << "rval elaboration error>;" << endl;
 
 }
 
diff --git a/net_func_eval.cc b/net_func_eval.cc
index 136be7805..58b7d629d 100644
--- a/net_func_eval.cc
+++ b/net_func_eval.cc
@@ -441,8 +441,11 @@ bool NetAssign::eval_func_lval_(const LineInfo&loc,
 bool NetAssign::evaluate_function(const LineInfo&loc,
 				  map<perm_string,LocalVar>&context_map) const
 {
-	// Evaluate the r-value expression.
-      NetExpr*rval_result = rval()->evaluate_function(loc, context_map);
+      // Evaluate the r-value expression.
+      const NetExpr*use_rval = rval();
+      if (use_rval == 0)
+	    return false;
+      NetExpr*rval_result = use_rval->evaluate_function(loc, context_map);
       if (rval_result == 0)
 	    return false;