sandbox/linux/bpf_dsl: eliminate implicit dependency on C++ compiler behavior

sandbox/linux/bpf_dsl/bpf_dsl.cc

 // 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.
 
 #include "sandbox/linux/bpf_dsl/bpf_dsl.h"
 
 #include <limits>
 
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
@@ skipping 100 matching lines @@
 };
 
 class IfThenResultExprImpl : public internal::ResultExprImpl {
  public:
   IfThenResultExprImpl(const BoolExpr& cond,
                        const ResultExpr& then_result,
                        const ResultExpr& else_result)
       : cond_(cond), then_result_(then_result), else_result_(else_result) {}
 
   CodeGen::Node Compile(PolicyCompiler* pc) const override {
-    return cond_->Compile(
-        pc, then_result_->Compile(pc), else_result_->Compile(pc));
+    // We compile the "then" and "else" expressions in separate statements so
+    // they have a defined sequencing.  See https://crbug.com/529480.
+    CodeGen::Node then_node = then_result_->Compile(pc);
+    CodeGen::Node else_node = else_result_->Compile(pc);
+    return cond_->Compile(pc, then_node, else_node);
   }
 
   bool HasUnsafeTraps() const override {
     return then_result_->HasUnsafeTraps() || else_result_->HasUnsafeTraps();
   }
 
  private:
   ~IfThenResultExprImpl() override {}
 
   BoolExpr cond_;
@@ skipping 232 matching lines @@
         new const IfThenResultExprImpl(clause.first, clause.second, expr));
   }
   return expr;
 }
 
 }  // namespace bpf_dsl
 }  // namespace sandbox
 
 template class scoped_refptr<const sandbox::bpf_dsl::internal::BoolExprImpl>;
 template class scoped_refptr<const sandbox::bpf_dsl::internal::ResultExprImpl>;