[C++] Add cplusplus component

components/cplusplus/README.md

+# C++ support for RT-Thread #
+
+This is the C++ component in RT-Thread RTOS. In order to support C++ language, this component
+implement a basic environment, such as new/delete operators.
+
+Because RT-Thread RTOS is used in embedded system mostly, there are some rules for C++ applications:
+1. DOES NOT use exception.
+2. DOES NOT use Run-Time Type Information (RTTI).
+3. Template is discouraged and it easily causes code text large.
+4. Static class variables are discouraged. The time and place to call their constructor function could not be precisely controlled and make multi-threaded programming a nightmare.
+5. Multiple inheritance is strongly discouraged, as it can cause intolerable confusion.
+
+*NOTE*: For armcc compiler, the libc must be enable.

components/cplusplus/SConscript

+# RT-Thread building script for component
+
+from building import *
+
+cwd = GetCurrentDir()
+src = Glob('*.cpp')
+CPPPATH = [cwd]
+
+group = DefineGroup('CPlusPlus', src, depend = ['RT_USING_CPLUSPLUS'], CPPPATH = CPPPATH)
+
+Return('group')

components/cplusplus/crt.cpp

+#include <rtthread.h>
+#include "crt.h"
+
+void *operator new(size_t size)
+{
+    return rt_malloc(size);
+}
+
+void *operator new[](size_t size)
+{
+    return rt_malloc(size);
+}
+
+void operator delete(void *ptr)
+{
+    rt_free(ptr);
+}
+
+void operator delete[] (void *ptr)
+{
+    return rt_free(ptr);
+}
+
+void __cxa_pure_virtual(void)
+{
+    rt_kprintf("Illegal to call a pure virtual function.\n");
+}

components/cplusplus/crt.h

+#ifndef CRT_H_
+#define CRT_H_
+
+#include <inttypes.h>
+#include <stdlib.h>
+
+void *operator new(size_t size);
+void *operator new[](size_t size);
+
+void operator delete(void * ptr);
+void operator delete[] (void *ptr);
+
+extern "C" void __cxa_pure_virtual(void);
+
+#endif