bpf_dsl: fix argument-dependent lookup of BoolExpr operators

sandbox/linux/bpf_dsl/bpf_dsl.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SANDBOX_LINUX_BPF_DSL_BPF_DSL_H_
 #define SANDBOX_LINUX_BPF_DSL_BPF_DSL_H_
 
 #include <stdint.h>
 
 #include <utility>
@@ skipping 245 matching lines @@
 
 // =====================================================================
 // Official API ends here.
 // =====================================================================
 
 // Definitions below are necessary here only for C++03 compatibility.
 // Once C++11 is available, they should be moved into bpf_dsl.cc via extern
 // templates.
 namespace internal {
 
+// Make argument-dependent lookup work.  This is necessary because although
+// BoolExpr is defined in bpf_dsl, since it's merely a typedef for
+// scoped_refptr<const internal::BoolExplImpl>, argument-dependent lookup only
+// searches the "internal" nested namespace.
+using bpf_dsl::operator!;
+using bpf_dsl::operator||;
+using bpf_dsl::operator&&;
+
 // Returns a boolean expression that represents whether system call
 // argument |num| of size |size| is equal to |val|, when masked
 // according to |mask|.  Users should use the Arg template class below
 // instead of using this API directly.
 SANDBOX_EXPORT BoolExpr
     ArgEq(int num, size_t size, uint64_t mask, uint64_t val);
 
 // Returns the default mask for a system call argument of the specified size.
 SANDBOX_EXPORT uint64_t DefaultMask(size_t size);
 
@@ skipping 73 matching lines @@
 
 template <typename T>
 ResultExpr Caser<T>::Default(ResultExpr result) const {
   return elser_.Else(result);
 }
 
 }  // namespace bpf_dsl
 }  // namespace sandbox
 
 #endif  // SANDBOX_LINUX_BPF_DSL_BPF_DSL_H_