Re: [PATCH] src/sort.c: assert on temp.text before calling memcpy()

[Pádraig Brady]

On 06/01/10 11:16, Kovarththanan Rajaratnam wrote:
> Pádraig Brady wrote:
> > That looks wrong.
> > Should memcpy() be marked as nonnull as the length can be 0?
> That doesn't matter:
>
> C99 7.21.1#2 "Where an argument declared as size_t n specifies
> the length of the array for a function, n can have the value
> zero on a call to that function. Unless explicitly stated
> otherwise in the description of a particular function in this
> subclause, pointer arguments on such a call shall still have
> valid values, as described in 7.1.4. On such a call, a
> function that locates a character finds no occurrence, a
> function that compares two character sequences returns zero,
> and a function that copies characters copies zero characters."

Seems like a silly memcpy implementation that would touch
the pointers when n==0

> > In any case we don't want to be asserting in such cases,
> > rather just doing:
> >
> > if (temp.text)
> >    memcpy (...)
> > From what I could gather all paths seem to lead to a temp.text which
> is non null. That is why I preferred the assert(). Is this assumption
> incorrect?

Having checked the code, I don't think it's incorrect
as line->length is >=1, though why couldn't clang figure that out?
Will we have to be putting asserts before loads of these
nonnull functions now?

cheers,
Pádraig