Segmentation fault on getline while parsing a file - c++

Question

I'm making a very simple file parser, in CSV style. The compilation runs smoothly, and when I run it, I'm having a segfault (core dumped). The only printed line is the one telling "Done" to say that the file succesfully opened. So my guess is that the Segfault happened during while(getline(myfile, line)).
Here's my code (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;
}
And my testfile.csv
version;1.3
###### SPECIE ######
SpecieID;Value1
VariantID;Value2
####################
##### IDENTITY #####
Name;Value3
DOName;Value4
####################
All files are in the same folder.
Do you have any clue why I'm having this segfault?
Thanks

Answer 1

Here is one obvious error, where you are accessing a vector's element out-of-bounds. Accessing an out-of-bounds element is undefined behavior.
else
{
vector <string> tmptokens;
if(verbose)
cout << "Adding token " << tmptokens[0] << " and its values.";
tokens.push_back(tmptokens);
}
Since tmptokens is empty, there is no tmptokens[0].
If the vector is empty, you could have done this:
else
{
if(verbose)
cout << "Adding new token and its values.";
tokens.push_back({});
}
There is no need to manually create an empty vector starting with C++11.