egcs-1.0.1 confused by explicit cast

[Richard Hadsell]

Jason Merrill wrote:
> 
>   5.2.9  Static cast                                  [expr.static.cast]
> 
> 2 An expression e can be explicitly  converted  to  a  type  T  using  a
>   static_cast  of the form static_cast<T>(e) if the declaration T t(e);"
>   is well-formed, for some invented temporary variable  t  (_dcl.init_).
>   The  effect  of  such an explicit conversion is the same as performing
>   the declaration and initialization and then using the temporary  vari-
>   able as the result of the conversion.
> 
> Since the above declaration is a direct-initialization, and so the
> candidates are the constructors of T, the same is true of a cast.  The cast
> notation does not have different semantics.

(a) I'm not using "static_cast<T>(e)".  I am using 5.4 -- "Explicit type
conversion (cast notation)."  I think you have missed 5.4 paragraph 4 --
"Any type conversion not mentioned below and not explicitly defined by
the user (_class.conv_) is ill-formed."  The reference "_class.conv_"
points to 12.3.  Clearly, explicit type conversions can be defined by
the user, as I did, and they are meant to be used when one tries to
convert to that type.

(b) The statement "a = b;" works, and it requires an implicit
conversion.  Since there are no standard conversions available, it must
use a user-defined conversion.  Only one user-defined conversion is
allowed, so it must be the conversion function.  There is no constructor
that will make this conversion.

(c) It makes no sense to say that "a = b;" does the right thing, but "a
= (A) b;" can't figure out what to do.  I am sure the standards
committee could not mean this.  For example, Josee Lajoie described type
conversions in C++ Report, 7:3 (3-4/95), pp. 40-46.  Look at the
"User-defined Conversions" section on p. 44.  I can't believe that the
standard has changed in something this basic.

(d) There are a number of compilers that have no trouble with this --
SGI's CC 7.1, both old and new compilers; KAI's KCC 3.2; gcc version
2.7.2.1; an old cfront CC on HP-UX.

Please take this seriously, so that I can take egcs seriously.

-- 
Dick Hadsell			914-381-8400  Fax: 914-381-9790
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