Hook to function

myFun.h

#include <stdio.h>

void __cyg_profile_func_enter(void *this_fn, void *call_site)
        __attribute__((no_instrument_function));
void __cyg_profile_func_enter(void *this_fn, void *call_site) {
    printf("Hello I am entering
");
} /* __cyg_profile_func_enter */
void __cyg_profile_func_exit(void *this_fn, void *call_site)
        __attribute__((no_instrument_function));
void __cyg_profile_func_exit(void *this_fn, void *call_site) {
    printf("Hello, I am exitint
");
} /* __cyg_profile_func_enter */

     main.c

#include <stdio.h>
#include "myfun.h"
void myStartupFun (void) __attribute__ ((constructor));
void myCleanupFun (void) __attribute__ ((destructor));
int foo() {
    return 2;
}
int bar() {
   return 1;
}
int main(int argc, char** argv) {
    int i ,j;
    i = foo();
    j = bar();
    printf("foo=%d bar=%d
", i, j);
    return 0;
}

when you compile this file, please put the myFun.h in the same directory with main.c, and MUST with flag “-finstrument-functions”