Re: Incorrect char extraction code

[Jason Merrill <jason at redhat dot com>]

>>>>> "Rosen," == Rosen, Hyman <Hyman.Rosen@kbcfp.com> writes:

> std_istream.h has the following pair of templates:
>   template<class _Traits>
>     basic_istream<char, _Traits>&
operator> (basic_istream<char, _Traits>& __in, unsigned char& __c)
>     { return (__in >> static_cast<char>(__c)); }

>   template<class _Traits>
>     basic_istream<char, _Traits>&
operator> (basic_istream<char, _Traits>& __in, signed char& __c)
>     { return (__in >> static_cast<char>(__c)); }

> These are clearly wrong; the result of a static_cast<char> is not an
> lvalue, so code that tries an extraction into a signed or unsigned char
> shouldn't even compile. Those casts need to be reinterpret_cast<char &>,

Yes.

> and then you need to verify that you won't run afoul of gcc's alias
> detection.

If it did, that would be a bug in the compiler; anything can be aliased by
a char*.

Jason