Why is there no division by zero compile time warning or run time crash in this code?

Question

class Divide
{
public:
    float divident, divisor;
    Divide():divident(10.0f),divisor(0.0f){}
};

int main()
{
    Divide obj[100];
    int quotient = obj[1].divident/obj[1].divisor;
    return quotient;
}

Edit: Compiler Qt 5.3.1 , Windows 7-32 bit.

Why is there no division by zero warning at compile time or a run time crash happening?

FWIW, I've used compilers that don't produce a compile time error when the division has a literal zero in the divisor. — Michael Burr, Dec 12 '14 at 08:50
Also, your compiler is not Qt. Qt is a library, not a compiler. — b4hand, Dec 12 '14 at 08:58

score 6 · Accepted Answer · answered Dec 12 '14 at 08:47

It doesn't crash because you've got a floating-point division by zero, not an integer division by zero. Floating-point division by zero is a valid way to obtain infinity.

The conversion from float to int is undefined, since infinity is not in int's range, so crashing would be allowed there, but that is simply not what typical implementations make it do.

score 0 · Answer 2 · answered Dec 12 '14 at 08:41

0

That's quite a code analysis you would be expecting on the part of the compiler in this particular case. I can't think of an existing compiler that would give you that level of analysis. I don't have much more of an answer than that.

answered Dec 12 '14 at 08:41

Jim Buck

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Why is there no division by zero compile time warning or run time crash in this code?

2 Answers2