Question

Consider the following method which reads a line from a text file and tokenizes it:

std::pair<int, int> METISParser::getHeader() {

    // handle header line
    int n;  // number of nodes
    int m;  // number of edges

    std::string line = "";
    assert (this->graphFile);
    if (std::getline(this->graphFile, line)) {
        std::vector<node> tokens = parseLine(line);
        n = tokens[0];
        m = tokens[1];
        return std::make_pair(n, m);
    } else {
        ERROR("getline not successful");
    }

}

A crash happens in std::getline (pointer being freed was not allocated – won’t go into the details here). The crash does not happen if I compile my code on other systems and is very likely not an error in my own code. For the moment I am unable to fix this, and I don’t have the time, so I’ll just try to bypass it with your help:

Can you suggest an alternative implementation that does not use std::getline?

EDIT: I am on Mac OS X 10.8 with gcc-4.7.2. I tried in on SuSE Linux 12.2 with gcc-4.7, where the crash does not happen.

EDIT: One guess was that parseLine corrupts the string. Here is the code for completeness:

static std::vector<node> parseLine(std::string line) {

    std::stringstream stream(line);
    std::string token;
    char delim = ' ';
    std::vector<node> adjacencies;

    // split string and push adjacent nodes
    while (std::getline(stream, token, delim)) {
        node v = atoi(token.c_str());
        adjacencies.push_back(v);
    }

    return adjacencies;
}

Answer 1

You can always write your own slower and simpler getline, just to make it work:

istream &diy_getline(istream &is, std::string &s, char delim = '\n')
{
    s.clear();
    int ch;
    while((ch = is.get()) != EOF && ch != delim)
        s.push_back(ch);
    return is;
]