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Std :: sort throws Segmentation Fault C ++

 3 years ago
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Std :: sort throws Segmentation Fault C ++

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Here's my code

bool cmp (const char &a, const char &b)
{
    if ((int) a == (int) b)
    {
        return false;
    }

    if ((int) a > (int) b)
    {
        return false;
    }
    return true;
}
std::sort(
        dfaVector.at(0).getSigma().begin(),
        dfaVector.at(0).getSigma().end(),
        cmp);

getSigma() returns std::vector<char> , and they aren't empty - I checked it. I can post stack trace from gdb if you want. I'm using g++ 4.8, OS Mint 14

ANSWER

As suggested by @livingissuicide the problem was that getSigma() needs to return a reference(i.e. sth constant, @PhoenixX_2). The explanation why it needs to return a reference (and why just a simple copy doesn't suffice) is because

The problem is that there are two calls to getSigma, producing two different vectors. A pair of iterators passed to sort is not a valid range - the two iterators point into different containers.

Explanation courtesy of @IgorTandetnik .

getSigma() returns std::vector< char >

Make sure your getSigma() function returns a reference (std::vector< char >&) rather than a copy!

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