C++/RAII: Could this cause a memory leak?

Question

I have a weird problem. I have written some MEX/Matlab-functions using C++. On my computer everything works fine. However, using the institute's cluster, the code sometimes simply stops running without any error (a core file is created which says "CPU limit time exceeded"). Unfortunately, on the cluster I cannot really debug my code and I also cannot reproduce the error.

What I do know is, that the error only occurs for very large runs, i.e., when a lot of memory is required. My assumption is therefore that my code has some memoryleaks.

The only real part where I could think of is the following bit:

#include <vector>

using std::vector;

vector<int> createVec(int length) {
    vector<int> out(length);

    for(int i = 0; i < length; ++i)
        out[i] = 2.0 + i; // the real vector is obviously filled different, but it's just simple computations

    return out;
}


void someFunction() {

    int numUser = 5;
    int numStages = 3;
    // do some stuff

    for(int user = 0; user < numUser; ++user) {

        vector< vector<int> > userData(numStages);

        for(int stage = 0; stage < numStages; ++stage) {
            userData[stage] = createVec(42);

            // use the vector for some computations
        }

    }
}

My question now is: Could this bit produce memory leaks or is this save due to RAII (which I would think it is)? Question for the MATLAB-experts: Does this behave any different when run as a mex file?

Thanks

There is undefined behavior. You didn't return a value from the function createVec. — PaulMcKenzie, Dec 28 '14 at 23:03
`"CPU limit time exceeded"` sounds like your program exceeds CPU time quota. — mip, Dec 28 '14 at 23:04
If you see the message "CPU limit time exceeded", why do think the problem is with memory leaks? — R Sahu, Dec 28 '14 at 23:05
try `ulimit -t some_value` command (or ask Mr Charlie root if you don't have permissions on that). — mip, Dec 28 '14 at 23:06
@PaulMcKenzie: Sorry, I missed the return-line. The newly created vector inside the function is returned. I edited the question — Chris, Dec 28 '14 at 23:08
@Chris - Well, the code you now posted doesn't show any memory leaks. — PaulMcKenzie, Dec 28 '14 at 23:09
@doc and RSahu: It's certainly not the CPU time quota. Unfortunately, our admin is on vacation for 2 more weeks -.- — Chris, Dec 28 '14 at 23:10
A good practice is for createVec to receive a vector by reference that way it doesn't have to copy the vector. — Benjy Kessler, Dec 28 '14 at 23:46
Another suggestion would be to try using c-style arrays and see if that helps. — Benjy Kessler, Dec 28 '14 at 23:47
You could also create userData only once instead of in every iteration. — Benjy Kessler, Dec 28 '14 at 23:55
@BenjyKessler: Returning `vector` is correct with (N)RVO and move semantic. — Jarod42, Dec 29 '14 at 02:07

C++/RAII: Could this cause a memory leak?

0 Answers0