mutil_thread附加字符串原因核心

Question

我使用多线程更新全局向量的每个项目（字符串） 每个线程更新项目（字符串）带有不同的索引 我认为是避免更新相同数据的好方法 但是我仍然得到核心，我不知道为什么

extern vector<string> gTestVec;
#define NUM 10

void * worker(void * args) {
  thread_data * p = (thread_data *)args;
  int i = p->thread_id;

  for (int j=0; j<100; j++) {
    gTestVec[i] += "a";
  }

  return NULL;
}


void do_complete_stage_test::excute() {
  int i = 0;
  pthread_t thd[NUM];
  thread_data data[NUM];

  for (i=0; i<NUM; i++) {
    gTestVec.push_back(format("%d", i));
    data[i].thread_id = i;
    
    if (0 != pthread_create(&(thd[i]), NULL, &worker, (void *)&data[i])) {
      printf("pthread_create failed");
    }
  }

  for (int i=0; i<NUM; i++) {
    if (0 != pthread_join(thd[i], NULL)) {
      printf("pthread_join failed");
    }
  }
}

在运行代码时，有时会得到Coredump

Starting program: /data/settle_script/isp_tran_collect/bin/isp_tran_collect -p 2134234
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
[New Thread 0x7ffff2623700 (LWP 6316)]
[New Thread 0x7fffefb0e700 (LWP 6317)]
[New Thread 0x7fffef30d700 (LWP 6318)]

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fffef30d700 (LWP 6318)]
0x00007ffff6787d67 in ?? () from /lib64/libstdc++.so.6
(gdb) bt
#0  0x00007ffff6787d67 in ?? () from /lib64/libstdc++.so.6
#1  0x00007ffff678899b in std::string::reserve(unsigned long) () from /lib64/libstdc++.so.6
#2  0x00007ffff6788bbf in std::string::append(char const*, unsigned long) () from /lib64/libstdc++.so.6
#3  0x000000000044babe in append (__s=0x880492 "a", this=<optimized out>) at /usr/include/c++/4.8.2/bits/basic_string.h:1009
#4  operator+= (__s=0x880492 "a", this=<optimized out>) at /usr/include/c++/4.8.2/bits/basic_string.h:942
#5  worker (args=<optimized out>) at ../src/do_complete_stage_test.cpp:21
#6  0x00007ffff7bc6e25 in start_thread () from /lib64/libpthread.so.0
#7  0x00007ffff5ee635d in clone () from /lib64/libc.so.6

感谢您的帮助！！！

Answer 1

在启动一些线程后，您可能会更改vector的容量。

防止向量重新分配和移动其内容的最简单方法是在启动第一个工作线程之前保留空间。

因此，请

gTestVec.reserve(NUM);

在循环前打电话。