On Fri, 17 Aug 2012 16:10:12 +0200
Markus Armbruster <arm...@redhat.com> wrote:
> Stefan Weil <s...@weilnetz.de> writes:
>
> > ccc-analyzer reports these warnings:
> >
> > monitor.c:3532:21: warning: Division by zero
> > val %= val2;
> > ^
> > monitor.c:3530:21: warning: Division by zero
> > val /= val2;
> > ^
> >
> > Rewriting the code fixes this (and also a style issue).
>
> I'm afraid this doesn't actually fix anything, because...
>
> > Signed-off-by: Stefan Weil <s...@weilnetz.de>
> > ---
> > monitor.c | 7 ++++---
> > 1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/monitor.c b/monitor.c
> > index 0c34934..0ea2c14 100644
> > --- a/monitor.c
> > +++ b/monitor.c
> > @@ -3524,12 +3524,13 @@ static int64_t expr_prod(Monitor *mon)
> > break;
> > case '/':
> > case '%':
> > - if (val2 == 0)
> > + if (val2 == 0) {
> > expr_error(mon, "division by zero");
> > - if (op == '/')
> > + } else if (op == '/') {
> > val /= val2;
> > - else
> > + } else {
> > val %= val2;
> > + }
> > break;
> > }
> > }
>
> ... expr_error() longjmp()s out. The expression evaluator commonly
> exploits that.
And that's correct. As far far I understood it's fixing clang, not qemu.
> If expr_error() returned, the code would be just as wrong after your
> patch as before.
Hmm, how? It checks for val2 == 0 first.
> Perhaps the checker can be shut up by making expr_error() QEMU_NORETURN.
That's indeed a better solution.
