c++ - std::vector 的赋值效果错误？

Question

错误代码如下:

#include <vector>
#include <string>
#include <iostream>
void foo(const std::vector<double> & in) {
  std::vector<const char *> v(5);
  size_t indx = 0; 
  for(auto & tmp : in) {
    auto temp = std::to_string(tmp);
    v[indx] = temp.c_str();
    std::cout << "right: "<< v[indx] << std::endl;
    indx += 1; 
  }
  std::cout << "wrong: " << v[0] << std::endl;
  std::cout << "wrong: " << v[1] << std::endl;
  std::cout << "wrong: " << v[2] << std::endl;
  std::cout << "wrong: " << v[3] << std::endl;
  std::cout << "wrong: " << v[4] << std::endl;
}

int main(int argc, char *argv[])
{
  std::vector<double> tmp = {0.01, 0.02, 0.03, 0.04, 0.05};
  foo(tmp);
  return 0; 
}

我编译代码，在for-loop中，打印正确，但外面打印错误，这里有什么问题？

Answer 1

错误是std::to_string(tmp)创建一个临时对象，该对象在分号后立即销毁。因此 c_str() 指针变为无效。

为什么不使用 std::vector<std::string>存储你的字符串？

std::vector<std::string> v(5);
size_t indx = 0; 
for(auto & tmp : in) {
  v[indx] = std::to_string(tmp);
  std::cout << "right: "<< v[indx] << std::endl;
  indx += 1; 
}