In case of code similar to this

struct v {
  union {
     struct { float a, b; }
     struct { float c[2]; }
  }
}

(it is more complicated than just this sample, to trigger this bug.
I can't easly produce small example)


file expression.c
method Expression *StructLiteralExp::semantic(Scope *sc)
performs kind of flatening, and adds member c to array "elements",
but in case on union memberrs it adds them as null:
relevant lines:
line 3373
 if (v->offset < offset)
 {   e = NULL;
     sd->hasUnions = 1;
 }


and line 3393
  elements->push(e)


Fix:
In file expression.c line 1477
method Expressions *Expression::arraySyntaxCopy(Expressions *exps)
add condition:

 for (int i = 0; i < a->dim; i++)
 {   Expression *e = (Expression *)exps->data[i];
-    e = e->syntaxCopy();
+   if (e)
+        e = e->syntaxCopy();
    a->data[i] = e;^M
 }


Without it, optimize.c lines 86-87 will call indirectly this method, when some (last) elemenets of exps is/are nulls, and segfault.