In this code:

#include <dlfcn.h>
#include <stddef.h>
#include <stdio.h>
#include "sync.h"

volatile clock_t sync_wait;

#define ORIG(func) _orig_##func
#define QUOTE(nm) #nm
// dirty hack
#define VOID1P , void* p1
#define VOID2P , void* p1, void* p2
#define INT2P  , int p1, int* p2
#define ACTUAL1 , p1
#define ACTUAL2 , p1, p2

#define INSTRUMENT(func, param, actual) \
static int (* ORIG(func))(void* p param) = NULL; \
int func (void * p param) { \
    clock_t t = clock(); \
    int ret = ORIG(func) (p actual); \
    t = clock() - t; \
    if(t > 5000) \
        sync_wait += t; \
    return ret; \
}

#define INIT(func) \
    ORIG(func) = dlsym(hndl, QUOTE(__##func))     // <<<< hndl is used here

INSTRUMENT(pthread_cond_wait, VOID1P, ACTUAL1)
INSTRUMENT(pthread_cond_timedwait, VOID2P, ACTUAL2)
INSTRUMENT(pthread_mutex_lock, , )
INSTRUMENT(pthread_mutex_setprioceiling, INT2P, ACTUAL2)
INSTRUMENT(pthread_rwlock_rdlock, , )
INSTRUMENT(pthread_rwlock_wrlock, , )

int init_sync_tracing() {
    sync_wait = 0;
    void* hndl = dlopen("libpthread.so", RTLD_LAZY); // <<<< hndl is marked as unused

    INIT(pthread_cond_wait);
    INIT(pthread_cond_timedwait);
    INIT(pthread_mutex_lock);
    INIT(pthread_mutex_setprioceiling);
    INIT(pthread_rwlock_rdlock);
    INIT(pthread_rwlock_wrlock);

    return (_orig_pthread_mutex_lock != NULL);
}


hndl is marked as unused. However it is heavily used in INIT macro.