add functions insturmentation example

Chapter02/README.md

@@ -3,8 +3,12 @@
 This folder contains examples in C++ from second chapter. 
 
 The folder contains following examples:
+- instrument_functions.cpp
 - vector_dyn_mem.cpp
 - vector_dyn_mem_reserve.cpp
 - vector_pmr.cpp
 - terminate_handler.cpp
 - new_deleted.cpp
+
+## Functions instrumentation in GCC
+Compile instrument_functions.cpp example using compiler flag -finstrument-functions

Chapter02/instrument_functions.cpp

@@ -0,0 +1,32 @@
+#include <cstdio>
+
+// Stub DWT_CYCCNT register
+#define DWT_CYCCNT 100
+
+extern "C"
+{
+    __attribute__((no_instrument_function)) void __cyg_profile_func_enter(void *this_fn, void *call_site)
+    {
+
+        printf("entry, %p, %d\n", this_fn, DWT_CYCCNT);
+    }
+
+    __attribute__((no_instrument_function)) void __cyg_profile_func_exit(void *this_fn, void *call_site)
+    {
+
+        printf("entry, %p, %d\n", this_fn, DWT_CYCCNT);
+    }
+}
+
+void fun()
+{
+    printf("Hi from fun!\n");
+}
+
+int main()
+{
+    fun();
+    printf("Hi from main!\n");
+
+    return 0;
+}