e-tok-deref-fix.patch

commit 78c9a67ec4e487058c215136594d4bbfe6185ca0
Author: Yichun Zhang (agentzh) <yichun@openresty.com>
Date:   Wed Oct 3 20:20:26 2018 -0700

    bugfix: a NULL deferef crash might happen in const_folder::visit_binary_expression() due to the fact that e->tok might be NULL.

    It is still not clear why e->tok would end of being NULL in the first
    place. Need investigations by tracing the full stap AST with stap (or
    gdb). The core dump can be easily reproduced by running the pyftrace
    ylang tool with 'stap -vvv' (and also without this patch).

    This patch is just a quick workaround for now.

diff --git a/elaborate.cxx b/elaborate.cxx
index 882d1f967..89dad2a7c 100644
--- a/elaborate.cxx
+++ b/elaborate.cxx
@@ -4618,7 +4618,7 @@ const_folder::visit_binary_expression (binary_expression* e)
                       (right->value <= 0 && (e->op == ">>" || e->op == "<<")))))
     {
       if (session.verbose>2)
-        clog << _("Collapsing constant-identity binary operator ") << *e->tok << endl;
+        clog << _("Collapsing constant-identity binary operator ") << e->op << endl;
       relaxed_p = false;

       // we'll pass on type=pe_long inference to the expression