widl: Write-strings warning fix.
diff --git a/tools/widl/parser.y b/tools/widl/parser.y
index 745056f..eb9b2c9 100644
--- a/tools/widl/parser.y
+++ b/tools/widl/parser.y
@@ -845,7 +845,7 @@
m_ident '{' cases '}' { var_t *u = $7;
$$ = get_typev(RPC_FC_ENCAPSULATED_UNION, $2, tsUNION);
$$->kind = TKIND_UNION;
- if (!u) u = make_var("tagged_union");
+ if (!u) u = make_var( xstrdup("tagged_union") );
u->type = make_type(RPC_FC_NON_ENCAPSULATED_UNION, NULL);
u->type->kind = TKIND_UNION;
u->type->fields = $9;