llvm-project/compiler-rt/test/tsan/memcmp_race.cc

// RUN: %clangxx_tsan -O1 %s -o %t && %deflake %run %t | FileCheck %s
#include "test.h"
#include <string.h>

char *data0 = new char[10];
char *data1 = new char[10];
char *data2 = new char[10];

void *Thread1(void *x) {
  static volatile int size = 1;
  static volatile int sink;
  sink = memcmp(data0+5, data1, size);
  barrier_wait(&barrier);
  return NULL;
}

void *Thread2(void *x) {
  static volatile int size = 4;
  barrier_wait(&barrier);
  memcpy(data0+5, data2, size);
  return NULL;
}

int main() {
  barrier_init(&barrier, 2);
  print_address("addr=", 1, &data0[5]);
  pthread_t t[2];
  pthread_create(&t[0], NULL, Thread1, NULL);
  pthread_create(&t[1], NULL, Thread2, NULL);
  pthread_join(t[0], NULL);
  pthread_join(t[1], NULL);
  return 0;
}

// CHECK: addr=[[ADDR:0x[0-9,a-f]+]]
// CHECK: WARNING: ThreadSanitizer: data race
// CHECK:   Write of size 1 at [[ADDR]] by thread T2:
// CHECK:     #0 {{(memcpy|memmove)}}
// CHECK:     #1 Thread2
// CHECK:   Previous read of size 1 at [[ADDR]] by thread T1:
// CHECK:     #0 memcmp
// CHECK:     #1 Thread1