Question

I’m compiling a program on remote linux server. The program compiled. However when I run it the program ends abruptly. So I debugged the program using DDT. It spits out the following error:

    Process 0:
    Memory error detected in ClassName::function (filename.cpp:6462).
    Thread 1 attempted to dereference a null pointer or execute an SSE instruction with an 
    incorrectly aligned memory address (the latter may sometimes occur spuriously if guard 
    pages are enabled)
    Tip: Use the stack list and the local variables to explore your program's current 
    state and identify the source of the error.

Can anyone please tell me what exactly this error means?

The line where the program stops looks like this:

    SumUtility = ParaEst[0] + hhincome * ParaEst[71] + IsBlack * ParaEst[61] + IsBachAss * (ParaEst[55]);

This is within a switch case.

These are the variable types

    vector<double> ParaEst;
    double hhincome;
    int IsBlack, Is BachAss;

Thanks for the help!

Answer 1

It means that:

1. ParaEst is NULL or a bad Pointer
2. ParaEst’s individual array values are not aligned to 16-byte boundaries, required for SSE.
3. hhincome, IsBlack, or IsBachAss are not aligned to 16-byte boundaries and are SSE type values.
4. SumUtility is not aligned to 16-bytes and is a SSE type field.

If you could post the assembly code of the exact line that failed along with the register values of that assembler line, we could tell you exactly which of the above conditions have failed. It would also help to see the types of each variable shown to help narrow root the cause.