C++ PATCH: 14035

[Kai Henningsen]

mark@codesourcery.com (Mark Mitchell)  wrote on 20.10.04 in <4176AB4F.8040208@codesourcery.com>:

> Gabriel Dos Reis wrote:
>
> >Nathan Sidwell <nathan@codesourcery.com> writes:
> >
> >| Mark Mitchell wrote:
> >|
> >| > On the other hand, I don't feel very strongly about that point of
> >| > view; if you and Jason think we should not issue a diagnostic, even
> >| > with -pedantic, that's OK with me.  Perhaps we could change the
> >| > pedwarn into a warning?  That would mean that it would not be an
> >| > error by default.  (The fact that pedwarns are errors by default
> >| > seems confused to me anyhow, but that's something where Jason and I
> >| > can't seem to persuade each other.)
> >|
> >| A warning would be fine in pedantic mode.
> >
> >I don't think -pedantic should be required.
> >
> >
> I do think it should be required.
>
> There's no point in warning by default about a technical violation of
> the standard for code that works on virtually all systems.  And I only
> say "virtually" because I'm not sure what obscure systems exist of which
> I am unaware; I do not know of any systems on which these casts would
> actually fail.

Presumably systems unsupported by gcc.

For example, there's an x86 (x<3) memory model where code and data are  
distinct 64kB segments, and pointers are 16 bit offsets. You might be able  
to have a data pointer that points to a function if those segments  
overlap, but you won't get it unless your cast knows what constant to add  
or subtract - and the pointer might not be in the overlap region.

Or in short, any system where you can have nonoverlapping code and data  
spaces.

MfG Kai