Re: undefined behaviour in lua source

[Daurnimator <quae@...>]

On 21 June 2016 at 15:17, Daurnimator <quae@daurnimator.com> wrote:
> On 21 June 2016 at 14:06, Sergey Zakharchenko <doublef.mobile@gmail.com> wrote:
>> Off the top of my head, there's something in your environment (gcc and
>> clang runtime?) that's configuring the FPU to raise exceptions instead
>> of return NaNs (via fesetexceptflag()?). Check with fegetexceptflag().
>
> As my post says, I see this output because I turned on the various
> sanitizers when compiling (which are designed to help you find where
> your code invokes undefined behaviour).
>
> In C, dividing a double by zero is undefined. From C89 draft standard
> http://port70.net/~nsz/c/c89/c89-draft.html#3.3.5:
>> The result of the / operator is the quotient from the division of the first operand by the second; the result of the % operator is the remainder. In both operations, if the value of the second operand is zero, the behavior is undefined.
>
> C99 has much the same to say: http://port70.net/~nsz/c/c99/n1256.html#6.5.5p5

I brought this up with dalias (author of musl) and he says this
section gets overridden by annex F.
clang's ubsan confusingly turns on -fsanitize=float-divide-by-zero

So, looks like this whole thing is a non-issue.