Merge pull request #3055 from NlightNFotis/fix_case_range_behaviour

Fix handling of case range statement in special case

Author: tautschnig

regression/ansi-c/goto_convert_switch_range_empty/test.desc

@@ -1,4 +1,4 @@
-KNOWNBUG
+CORE
 main.c
 
 ^EXIT=0$

regression/ansi-c/goto_convert_switch_range_empty_nodefault/main.c

@@ -0,0 +1,10 @@
+int main()
+{
+  int x;
+  switch(x)
+  {
+  case 10 ... 0:
+    break;
+  }
+  return 0;
+}

regression/ansi-c/goto_convert_switch_range_empty_nodefault/test.desc

@@ -0,0 +1,8 @@
+CORE
+main.c
+
+^EXIT=0$
+^SIGNAL=0$
+--
+^warning: ignoring
+^Invariant check failed

src/goto-programs/goto_convert.cpp

@@ -1249,7 +1249,8 @@ void goto_convertt::convert_switch(
   {
     const caset &case_ops=case_pair.second;
 
-    assert(!case_ops.empty());
+    if (case_ops.empty())
+      continue;
 
     exprt guard_expr=case_guard(argument, case_ops);