vafeiadis ( Viktor Vafeiadis )

In case a __VERIFIER_assume condition only depends on one remaining atomic read, and between the atomic read and the __VERIFIER_assume no other memory operations are generated, we do not need to explore the graphs in which the atomic read results in a blocked execution.

The code below should result in 1 execution but results in 2^NTHREADS many executions (of which all but 1 are blocked).


#include <pthread.h>
#include <assert.h>

#include <stdatomic.h>

#ifndef NTHREADS
#define NTHREADS 3
#endif

#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>

#include <genmc.h>



struct task {
    atomic_bool run_worker;
} TASK[NTHREADS];

void *run(void * task_v) {
    struct task *task = task_v;
    __VERIFIER_assume(task->run_worker);
    return 0;
}



int main()
{
        pthread_t t[NTHREADS];
        for (size_t i = 0; i < NTHREADS; i++)
        {
            TASK[i].run_worker = false;
            pthread_create(&t[i], 0, run, &TASK[i]);
            TASK[i].run_worker = true;
        }

        
        for (uintptr_t i = 0; i < NTHREADS; i++)
                pthread_join(t[i], NULL);

        return 0;
}

closed time in 20 days

JonasOberhauser

issue commentMPI-SWS/genmc

Avoid blocked executions when reading with __VERIFIER_assume

Thanks again for the suggestion, Jonas. GenMC v0.6 does something similar for assume statements.

JonasOberhauser

comment created time in 20 days

issue commentMPI-SWS/genmc

free(NULL)

Fixed in v0.6.

JonasOberhauser

comment created time in 20 days

issue closedMPI-SWS/genmc

free(NULL)

Is a nop in C, but segfaults in GenMC

closed time in 20 days

JonasOberhauser

issue closedMPI-SWS/genmc

malloc + pthread_mutex_init does not seem to work

#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>

typedef struct {
  pthread_mutex_t m;
} lock;

int main(void) 
{
 lock *t = malloc(sizeof(lock));
 pthread_mutex_init(&t->m, NULL);
 pthread_mutex_lock(&t->m);
 return 0;
}

Considered access to uninitialized memory

closed time in 20 days

JonasOberhauser

issue commentMPI-SWS/genmc

malloc + pthread_mutex_init does not seem to work

This is fixed in v0.6.

JonasOberhauser

comment created time in 20 days

push eventMPI-SWS/genmc

Michalis Kokologiannakis

commit sha 1142c61028eea365c01a2d370210b6350ce2452f

Delete unused script