new file mode 100644

@@ -0,0 +1,19 @@

+#include <cstdlib>

+#include <memory>

+

+#include "sys_stdlib.h"

+

+namespace {

+    class impl : public stdlib_ifc {

+        public:

+            int rand() const override {

+                return ::rand();

+            }

+

+    };

+}

+

+stdlib const &stdlib::get() {

+    static stdlib singleton {std::make_shared<impl>()};

+    return singleton;

+}

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@@ -0,0 +1,23 @@

+#ifndef SYS_CSTDLIB_H_

+#define SYS_CSTDLIB_H_

+

+#include <memory>

+

+class stdlib_ifc {

+    public:

+        virtual int rand() const {return 0;}

+};

+

+class stdlib {

+    public:

+        using delegate = std::shared_ptr<stdlib_ifc>;

+    private:

+       delegate delegate_;

+    public:

+       stdlib(delegate delegate = std::make_shared<stdlib_ifc>()) : delegate_(delegate) {}

+      int rand() const { return delegate_->rand(); }

+      static const stdlib& get();

+};

+

+

+#endif