[cfe-commits] [Patch] Add a warning for for loops with conditions that do not change

[Richard Trieu]

On Mon, Feb 6, 2012 at 2:02 PM, Eli Friedman <eli.friedman at gmail.com> wrote:

> On Mon, Feb 6, 2012 at 1:55 PM, Richard Trieu <rtrieu at google.com> wrote:
> > The motivation of this path is to catch code like this:
> >
> > for (int i = 0; i < 10; ++i)
> >   for (int j = 0; j < 10; ++i)
> >     { }
> >
> > The second for loop increments i instead of j causing an infinite loop.
>  The
> > warning also checks the body of the for loop so it will trigger on:
> >
> > for (int i; i <10; ) { }
> >
> > But not trigger on:
> >
> > for (int i; i< 10; ) { ++i; }
> >
> > I'm still fine-tuning the trigger conditions, but would like some
> feedback
> > on this patch.
>
> Adding an additional recursive traversal of the body of every parsed
> for loop is very expensive.
>
> -Eli
>

Is it that expensive?  I would think that once the AST was constructed, the
visitor would be pretty fast, especially if no action is taken on most of
the nodes.  I also made the warning default ignore and put in an early
return to prevent the visitors from running in the default case.

Do you have any suggestions on removing the recursive traversal?
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