[PATCH] D10634: Loss of Sign Checker

[Daniel Marjamäki]

danielmarjamaki added a comment.

In http://reviews.llvm.org/D10634#217441, @soumitra wrote:

> In http://reviews.llvm.org/D10634#217438, @danielmarjamaki wrote:
>
> > In http://reviews.llvm.org/D10634#217433, @soumitra wrote:
> >
> > > In http://reviews.llvm.org/D10634#213835, @zaks.anna wrote:
> > >
> > > > I am leaning toward allowing explicit assignments to "-1", like in this case: "unsigned int j = -1". The tool is much more usable if there are few false positives.
> > >
> > >
> > > This is exactly what I started off with, albeit with a plain 'char' instead of 'unsigned int'. We were hitting a runtime issue while porting a large piece of software to AArch64 since the "signedness" of plain char changes across x86 and AArch64, and a negative value was used as a initializer.
> >
> >
> > I am also still skeptic about this. Ideally there should only be warnings when there is a mistake.
> >
> > In your example code you showed previously there were portability problems because the signedness changed. A warning for that is ok in my opinion.
> >
> > If the code says 'unsigned int j = -1;' then there is no such portability problem.
>
>
> Ah! Now I get it!!
>
> So, the case I have is assignment of a negative value to a 'plain char'. Is there a way I can check for a 'plain char' in the checker as against a generic 'unsigned' integral variable?


Great. I don't know how off the top of my head. But it should be possible.


http://reviews.llvm.org/D10634