访问对象向量内的对象时出现分割错误

我在尝试访问存储在向量中的对象时遇到分段错误。我有一个由流程组成的调查。每个过程都由问题组成。因此，调查对象包含一个或多个流程，每个流程对象包含一个问题向量。类定义如下：

class Survey {
private:
...
vector <Process> survey_processes;
....
public:
......
vector<Process> getSurveyProcesses()
{ return survey_processes;  }
void addProcessObj(Process obj)
{ survey_processes.push_back(obj);}
.....
};
class Process
 { 
private:
....
vector<Question> proc_questions;
....
public:
...
vector<Question> getProcessQuestions()
{ return proc_questions;}
void addQuestionObj(Question obj)
{ proc_questions.push_back(obj); }
.....
};
class Question {
private:
int quesnum;
int answer;
...
public:
Question (int c_ques, int c_ans)
{
quesnum = c_ques;
answer = c_ans;
}
int getQuestionID()
{
    return quesnum;
} 
int getAnswer()
{
    return answer;
}
...
};

时，我将其存储在流程向量中，对于每个流程对象，我将问题对象推送到问题向量中。对于调查对象，我想从流程向量中获取每个流程，对于每个流程对象，获取每个问题对象并打印出来。

我可以使用以下代码访问流程对象并成功打印它们。

cout << ((survey_obj.getSurveyProcesses()).back()).getProcessID() << endl;

当我尝试从流程向量中提取问题对象时，它给了我一个分割错误。我相信我在尝试访问该对象时犯了一些语法错误。 如何访问嵌入在给定流程对象的问题向量中的问题对象，该向量位于给定调查对象的流程对象向量内？

下面是发生分段错误的代码的相关部分。

int procnum = 0;
for (unsigned i = 11; i < all_words.size()-1; ++i)
{   
vector<string> v;
string s = all_words.at(i);
stringstream ques_stream(s);
int ques_num;
ques_stream >> ques_num;
ques_stream.ignore();   
// if process object already exists, do nothing. Otherwise create a new process object and add it to the survey object  
if (procnum == ques_num)
    ;
else    
{   
Process proc_obj(ques_num);
survey_obj.addProcessObj(proc_obj);
procnum = ques_num;
}
string ques_strng;  
ques_stream >> ques_strng;
ques_stream.ignore();
Question ques_obj(ques_strng);
// objective: put the new question object in the question vector of the last process object from the process vector of the survey object
cout << ((survey_obj.getSurveyProcesses()).back()).getProcessID() << endl;
Process current_proc_obj = (survey_obj.getSurveyProcesses()).back();
cout << " Current Process : " << current_proc_obj.getProcessID() << endl;
Question current_question_obj = (current_proc_obj.getProcessQuestions()).back();

((survey_obj.getSurveyProcesses()).back()).addQuestionObj(ques_obj);    
**// this is where the segmentation fault occurs when i try to get the last object from process vector of the survey and for that object get the last element of the question vector. print the question id of this question object     
cout << " Current Question : " << ((((survey_obj.getSurveyProcesses()).back()).getProcessQuestions()).back()).getQuestionID() << endl;**
cout << " Current Process Question : " << ((current_proc_obj.getProcessQuestions()).back()).getQuestionID() << endl;
}

我尝试运行 gdb 调试器，但它只告诉我在尝试访问 questionID 时发生错误。我仍然不知道我做错了什么，任何帮助将不胜感激。