Question

I have the following LLVM code. The strange thing is that the si variable of type StoreInst becomes null(0) immediately after it is allocated with new instruction outside the if block, whereas I have declared it at an outer scope. What is going on here?

        Value *OldVal = NULL;
        StoreInst* si = NULL;

        if ( ... )
        {
            if ( ... )
            {
                ....

                if ( ... )
                {
                    ...
                    StoreInst* si = new StoreInst(...);
                    errs() << "si = " << si << "\n"; // Get some address here
                }
                errs() << "-->SI = " << si << "\n"; // Here I get NULL, why?
            }
            ...
        }

I get an output like this,

si = 0x1822ba0
-->SI = 0x0

Answer 1

StoreInst* si = new StoreInst(...); – You hidden the previos name si here

When the scope is ended } – you see the value of another pointer

Here is an example of what you did:

int val = 0; //first val
{
    int val = 10; //other val (let's call it second)
    cout << val; //second val
} // second val is destroyed here
cout << val; //first val

I’ve used int in the example for simplicity. Actually it can be any type