解析文件时 getline 上的分段错误

Question

我正在制作一个非常简单的 CSV 格式的文件解析器。编译运行很顺利，当我运行它时，我遇到了段错误（核心已转储）。唯一打印的行是告诉 "Done" 文件已成功打开的行。所以我的猜测是段错误发生在 while(getline(myfile, line)).

期间

这是我的代码 (parser.cpp):

#include "parser.h"

vector<string> str_explode(string const & s, char delim)
{
    vector<string> result;
    istringstream iss(s);

    for (string token; getline(iss, token, delim); )
    {
        result.push_back(move(token));
    }
    return result;
}

vector<vector<string>> getTokensFromFile(string fileName)
{
    bool verbose = true;
    if(verbose)
        cout << "Entering getTokensFromFile(" << fileName << ")" << endl ;
    /* declaring what we'll need :
     * string line -> the line beeing parsed
     * ifstream myfile -> the file that name has been given as parameter
     * vector <vector <string> > tokens -> the return value
     * 
     * Putting all line into tokens
     */

    string line;
    ifstream myfile(fileName);
    vector< vector<string> > tokens;
    if(verbose)
        cout << "Opening file " << fileName << " ... ";
    if (myfile.is_open())
    {
        if(verbose)
            cout << "Done !" << endl;
        while (getline (myfile,line))
        {
            if(verbose)
                cout << "Parsing line '" << line << "'. ";
            // If line is blank or start with # (comment)
            // then we don't parse it
            if((line.length() == 0) || (line.at(0) == '#'))
            {
                if(verbose)
                    cout << "Empty or comment, passing.";
                continue;
            }
            else
            {
                vector <string> tmptokens;
                if(verbose)
                    cout << "Adding token " << tmptokens[0] << " and its values.";
                tokens.push_back(tmptokens);
            }
            cout << endl;
        }
    }
    else
    {
        cout << "Unable to open file " << fileName << endl;
        throw exception();
    }
    if(verbose)
        cout << "Exiting getTokensFromFile(" << fileName << ")" << endl;
    return tokens;
}

main.cpp

#include "parser.h"

int main()
{
    getTokensFromFile("testfile.csv");
    return 0;
}

还有我的testfile.csv

version;1.3
###### SPECIE ######
SpecieID;Value1
VariantID;Value2
####################

##### IDENTITY #####
Name;Value3
DOName;Value4
####################

所有文件都在同一个文件夹中。

你知道我为什么会出现这个段错误吗？

谢谢

Answer 1

这是一个明显的错误，您越界访问向量的元素。访问越界元素是未定义的行为。

   else
   {
       vector <string> tmptokens;
       if(verbose)
           cout << "Adding token " << tmptokens[0] << " and its values.";
       tokens.push_back(tmptokens);
   }

因为tmptokens是空的，所以没有tmptokens[0]。

如果向量为空，您可以这样做：

   else
   {
       if(verbose)
           cout << "Adding new token and its values.";
       tokens.push_back({});
   }

无需手动创建从 C++11 开始的空向量。

解析文件时 getline 上的分段错误

Segmentation fault on getline while parsing a file

c++

segmentation-fault