-Wconversion versus libstdc++

[Paolo Carlini]

Martin Sebor wrote:

> FYI: HP aCC warns for some but not all of these types of lossy
> initializations. For example, a double to int conversion emits
> a warning but ptrdiff_t to size_t or other signed to unsigned
> conversions do not, probably because they're so common. I find
> this behavior useful.

Thanks Martin for the data point: I understand that this behavior is 
typical of the compilers based on the EDG front-end?

Anyway, note that our -Wconversion is not part of -Wall, not even 
-Wextra: are you maintaining that probably the bits having to do with 
float <-> integer should also be part of -Wall or at least -Wextra? For 
convenience this is the manual entry for -Wconversion:

|-Wconversion|
    Warn for implicit conversions that may alter a value. This includes
    conversions between real and integer, like |abs (x)| when |x| is
    |double|; conversions between signed and unsigned, like |unsigned ui
    = -1|; and conversions to smaller types, like |sqrtf (M_PI)|. Do not
    warn for explicit casts like |abs ((int) x)| and |ui = (unsigned)
    -1|, or if the value is not changed by the conversion like in |abs
    (2.0)|.
Paolo.