On Tue, 9 Oct 2001, Helmut Zeisel wrote:
>
> Must this code compile?
>
> std::ios_base::iostate err=0;

No.
>
> GCC 3.0.1 insists says
> "cannot convert `int' to `std::_Ios_Iostate' in initialization".

That's allowed.

>
> This line works:
>
> std::ios_base::iostate err=std::ios_base::goodbit;

Yes, it must.

The standard allows iostate to be implemented as an integer,
as an enumated type that overloads some arithmetic operations,
or as a bitset. There is no requirement that you be able to
assign an integer value to it.

Refer to C++ standard, 27.4.2.1.3 "Type ios_base::iostate" and
17.3.2.1.2 "Bitmask types".

--
Steve Clamage, stephen.clamage@sun.com

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Must this code compile?

std::ios_base::iostate err=0;

GCC 3.0.1 insists says
"cannot convert `int' to `std::_Ios_Iostate' in initialization".

This line works:

std::ios_base::iostate err=std::ios_base::goodbit;

Is the behavior of GCC 3.0.1 standard conform?

Helmut

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Helmut Zeisel wrote:
>
> Must this code compile?
>
> std::ios_base::iostate err=0;
>
> GCC 3.0.1 insists says
> "cannot convert `int' to `std::_Ios_Iostate' in initialization".
>
> This line works:
>
> std::ios_base::iostate err=std::ios_base::goodbit;
>
> Is the behavior of GCC 3.0.1 standard conform?
>
iostate is a bitmask, which is an enum type (with some additional helpers).
Integers (even zero) do not convert implicitly to enum type.  You'll have to
cast it.

There is even an example in the C++ standard that is wrong (21.1.1/3).
If you want to do this you want to assign "goodbit"

 std::ios_base::iostate = std::ios_base::goodbit;

-Ron
Welcome to Good Bit home of the Good Bit.

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Ron Natalie wrote:
>
> >
> iostate is a bitmask, which is an enum type (with some additional helpers).

A bitmask type can be an enumerated type with overloaded operators, an
integer type, or a bitset. Which doesn't change the fact that 0 isn't an
appopriate initializer...

> Integers (even zero) do not convert implicitly to enum type.  You'll have to
> cast it.
>
> There is even an example in the C++ standard that is wrong (21.1.1/3).
> If you want to do this you want to assign "goodbit"
>
>         std::ios_base::iostate = std::ios_base::goodbit;
>
--
Pete Becker
Dinkumware, Ltd. (http://www.dinkumware.com)

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Ron Natalie wrote:
>
> Helmut Zeisel wrote:
> >
> > Must this code compile?
> >
> > std::ios_base::iostate err=0;
> >

>
> There is even an example in the C++ standard that is wrong (21.1.1/3).

I think you mean 22.1.1/3
Similar code is also in 27.6.1.2.2

This was why I thought that GCC might be wrong.
As I understand now these are typos in the standard and GCC is right.

Helmut

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