[cfe-dev] david's integer overflow stuff

[Chris Lattner]

On Sep 10, 2010, at 2:51 PM, David Chisnall wrote:
>>> Chris, I note that you made this change last month, without any discussion, removing the original, generic, behaviour that was discussed on-list, in favour of GCC's more limited behaviour which does not provide options for recovery.  
>> 
>> I thought that I emailed you or cc'd you on the commit.  But yes you're right.  -ftrapv is a gcc flag and we got numerous bug reports from people who were trying to use it and getting link errors.
> 
> Numerous?  I think I remember two.  Anyway, that would have been a good reason for starting a discussion, not a good reason for removing a feature that has been in clang for over a year and that people are using.

I thought I emailed you about this.  In any case, I don't think that there is any reasonable discussion to be had: it's the wrong thing to do for -ftrapv, as I said before, it breaks an established model.  Adding a new option that does the new behavior may be reasonable.

>> I didn't realize that you were implementing it in a gcc compatible way.
> 
> I provided a default handler function that would call abort (after printing a helpful error) along with the original patch.  It never got committed (I didn't have commit access back then, other people were committing my patches).  Mike said it would go in a clang runtime lib when one existed.

Are you sure that I approved the patch and not mike?  Do you have a link?

In any case, it doesn't matter if you patch included it or not, the end result is that the compiler was broken.  It was reported in more than two places.

-Chris