Question

I have a code with possible floating point overflows which cannot be managed by checking arguments of functions. I have to define _matherr and throw an exception from inside it in order to give a chance to caller to manage the problem.

There is something strange: in Debug build, _matherr is called as supposed, but not in Release. I use CodeGear C++ Builder 2007. Under MSVC 2010 the handler works fine, but I need VCL features for the whole application. Googling gives nothing but messages about _matherr not working in DLL (that is known from documentation).

And my question is: what could be the reason for _matherr to not work in Release?

// One of the methods with overflows.
double DoubleExponential::F(double x) const
{
    try
    {
        double y=pow(fabs(x),a);
        return 0.5 + sign(x)*G(y,1/a)/(2*G(1/a));
    }
    catch(PowExpOverflow)
    {
        return 0.5;
    }
}

// Exception.
struct PowExpOverflow {};

int _matherr (struct _exception *a){
    Application->MessageBox("Inside custom _matherr", "", MB_OK);
    if (a->type == OVERFLOW)
        if (!strcmp(a->name,"pow") ||
            !strcmp(a->name,"powl") ||
            !strcmp(a->name,"exp") ||
            !strcmp(a->name,"expl"))
        {
            throw PowExpOverflow();
        }
    return 0;
}

Answer 1

The problem is due to bug in the dynamic RTL which I use in the release build (description). The bug was not fixed in the version of IDE I use, so the only working solution is to upgrade to a higher version. Nevertheless, having a clear explanation helps a lot.