Segmentation fault: 11 while printing dynamic arrays

问题

I have a simple C++ code where I define a dynamic array as:

std::vector<double>IPWeights;

and then pass it to a function called reference with a reference (so I changed its content) like:

void reference (std::vector<double> &IPWeights)

and then in my main function, after I changed my arrays content I wanted to print it like:

int size_weights=IPWeights.size();

for (int i=0; i<size_weights; i++)
{
    std::cout<<IPWeights[i]<<std::endl;
}

but in the screen I only see "segmentation fault 11".

where the reference is simply looks like:

void reference( std::vector<double> &IPWeights)
{
    IPWeights[0]=0.4500;
    IPWeights[1]=0.2648;
    IPWeights[2]=0.2648;
    IPWeights[3]=0.2648;
    IPWeights[4]=0.2519;
    IPWeights[5]=0.2519;
    IPWeights[6]=0.2519;
}

Any advice is appreciated, Thanks in advance.

回答1:

My crystal ball says that you don't allocate memory for the vector. You should do one of the following:

• Initialize vector with appropriate size:

  std::vector<double> IPWeights(size_you_need);
  

• Call IPWeights.resize() before assigning to it:

  std::vector<double> IPWeights;
  IPWeights.resize(size_you_need);
  

• Call IPWeights.push_back() instead of assigning by index:

  IPWeights.push_back(0.4500);
  IPWeights.push_back(0.2648);
  //...
  

来源：https://stackoverflow.com/questions/27400767/segmentation-fault-11-while-printing-dynamic-arrays