Updated README and Examples

Fixed a bunch of issues with the original examples, and removed
all of the performance stuff as the point of the pattern is not
to argue about the performance costs of pure virtual, but instead
to simply show how to do abstraction without the need for pure
virtual.

Author: rianquinn

CMakeLists.txt

@@ -26,12 +26,12 @@ include(ExternalProject)
 # ------------------------------------------------------------------------------
 
 set(CMAKE_CXX_STANDARD 17)
-set(CMAKE_EXE_LINKER_FLAGS "-Wl,--strip-all")
+# set(CMAKE_EXE_LINKER_FLAGS "-Wl,--strip-all")
 
 # ------------------------------------------------------------------------------
 # source
 # ------------------------------------------------------------------------------
 
 add_subdirectory(bad)
-add_subdirectory(dynamic_abstraction)
-add_subdirectory(static_abstraction)
+add_subdirectory(dynamic_interface)
+add_subdirectory(static_interface)

README.md

@@ -16,10 +16,5 @@
 # License along with this library; if not, write to the Free Software
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 
-add_executable(bad a.cpp b.cpp main.cpp)
-add_executable(bad_ut b.cpp unittest.cpp)
-add_executable(bad_perf a.cpp b.cpp performance.cpp)
-
-target_compile_options(bad PRIVATE -O3 -DNDEBUG)
-target_compile_options(bad_ut PRIVATE -g)
-target_compile_options(bad_perf PRIVATE -O3 -DNDEBUG)
+add_executable(bad main.cpp)
+target_compile_options(bad PRIVATE -O3)

bad/CMakeLists.txt

@@ -22,10 +22,13 @@
 #ifndef A_H
 #define A_H
 
+static volatile int g_count;
+#define NOINLINE __attribute__ ((noinline))
+
 class A
 {
 public:
-    void foo();
+    void NOINLINE foo() { g_count += 1; }
 };
 
 #endif

bad/a.cpp

@@ -24,9 +24,13 @@
 
 #include "a.h"
 
-struct B
+class B
 {
-    void bar();
+public:
+    void bar()
+    { m_a.foo(); }
+
+private:
     A m_a;
 };
 

bad/a.h

@@ -16,10 +16,8 @@
 # License along with this library; if not, write to the Free Software
 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 
-add_executable(static_abstraction a.cpp b.cpp main.cpp)
-add_executable(static_abstraction_ut a.cpp b.cpp unittest.cpp)
-add_executable(static_abstraction_perf a.cpp b.cpp performance.cpp)
+add_executable(dynamic_interface main.cpp)
+add_executable(dynamic_interface_ut unittest.cpp)
 
-target_compile_options(static_abstraction PRIVATE -O3 -DNDEBUG)
-target_compile_options(static_abstraction_ut PRIVATE -g)
-target_compile_options(static_abstraction_perf PRIVATE -O3 -DNDEBUG)
+target_compile_options(dynamic_interface PRIVATE -O3)
+target_compile_options(dynamic_interface_ut PRIVATE -O3)

bad/b.cpp

@@ -22,17 +22,16 @@
 #ifndef A_H
 #define A_H
 
-#include "interface.h"
+#include "a_interface.h"
+
+static volatile int g_count;
+#define NOINLINE __attribute__ ((noinline))
 
 class A :
-    public interface<A>
+    public AInterface
 {
-    struct details {
-        void foo();
-    };
-
-    details d;
-    friend class interface<A>;
+public:
+    void NOINLINE foo() override { g_count += 1; }
 };
 
 #endif

bad/b.h

@@ -19,13 +19,13 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#ifndef INTERFACE_H
-#define INTERFACE_H
+#ifndef A_INTERFACE_H
+#define A_INTERFACE_H
 
-class interface
+class AInterface
 {
 public:
-    virtual ~interface() = default;
+    virtual ~AInterface() = default;
     virtual void foo() = 0;
 };
 

bad/performance.cpp

@@ -22,14 +22,22 @@
 #ifndef B_H
 #define B_H
 
-#include "interface.h"
+#include "b_interface.h"
+#include "a_interface.h"
 
-struct B
+class B :
+    public BInterface
 {
-    B(interface *a);
+public:
+    B(AInterface *a) :
+        m_a{a}
+    { }
 
-    void bar();
-    interface *m_a;
+    void bar() override
+    { m_a->foo(); }
+
+private:
+    AInterface *m_a;
 };
 
 #endif

bad/unittest.cpp

@@ -19,16 +19,14 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-#ifndef A_H
-#define A_H
+#ifndef B_INTERFACE_H
+#define B_INTERFACE_H
 
-#include "interface.h"
-
-class A :
-    public interface
+class BInterface
 {
 public:
-    void foo() override;
+    virtual ~BInterface() = default;
+    virtual void bar() = 0;
 };
 
 #endif