Makefile

all: mutator mutatee

mutator: mutator.o
	g++ mutator.o -L/usr/lib/dyninst -ldyninstAPI -o mutator
mutatee: mutatee.o
	gcc mutatee.o -std=gnu99 -g -o mutatee -lrt
mutatee.o: mutatee.c
	gcc mutatee.c -std=gnu99 -g -c -o mutatee.o

mutatee.c

#include <stdio.h>
#include <unistd.h>
#include <time.h>

#define tic() do { struct timespec ts_start, ts_end; clock_gettime(CLOCK_MONOTONIC, &ts_start)
#define toc() clock_gettime(CLOCK_MONOTONIC, &ts_end); \
              printf("%lfs\n", (ts_end.tv_sec - ts_start.tv_sec) + (double)(ts_end.tv_nsec - ts_start.tv_nsec)/1e9); } \
              while (0)

void foo() {
    sleep(1);
    printf("I am foo()\n");
    return;
}

void bar() {
    printf("I am bar()\n");
    return;
}

int main()
{
    printf("Hello World!\n");
    
    tic();
    for (int i = 0; i < 10; ++i)
        foo();
    toc();

    return 0;
}

mutator.cpp

#include <dyninst/BPatch.h>
#include <dyninst/BPatch_point.h>
#include <dyninst/BPatch_function.h>
#include <vector>

int main (int argc, const char* argv[]) {
    BPatch bpatch;
    BPatch_process *proc = bpatch.processCreate(argv[1], argv + 2);
    //bpatch.setTrampRecursive(true);
    //bpatch.setSaveFPR(false);
    //bpatch.setInstrStackFrames(false);
    //BPatch_process *proc = bpatch.processAttach(argv[1], atoi(argv[2]));
    BPatch_image *image = proc->getImage();

    std::vector<BPatch_function *> foo_fns, bar_fns;
    image->findFunction("foo", foo_fns);
    image->findFunction("bar", bar_fns);

    std::vector<BPatch_snippet*> args;
    BPatch_funcCallExpr call_bar(*bar_fns[0], args);
    proc->insertSnippet(call_bar, (foo_fns[0]->findPoint(BPatch_entry))[0]);

    proc->continueExecution();
    //proc->detach(true);
    while (!proc->isTerminated()) {
        bpatch.waitForStatusChange();
    }

    return 0;
}

output

Hello World!
I am bar()
I am foo()
I am bar()
I am foo()
I am bar()