Return-Path: 
 <dev-return-7236-apmail-stdcxx-dev-archive=stdcxx.apache.org@stdcxx.apache.org>
Delivered-To: apmail-stdcxx-dev-archive@www.apache.org
Received: (qmail 76196 invoked from network); 2 Apr 2008 21:10:13 -0000
Received: from hermes.apache.org (HELO mail.apache.org) (140.211.11.2)
  by minotaur.apache.org with SMTP; 2 Apr 2008 21:10:13 -0000
Received: (qmail 60523 invoked by uid 500); 2 Apr 2008 21:10:13 -0000
Delivered-To: apmail-stdcxx-dev-archive@stdcxx.apache.org
Received: (qmail 60500 invoked by uid 500); 2 Apr 2008 21:10:13 -0000
Mailing-List: contact dev-help@stdcxx.apache.org; run by ezmlm
Precedence: bulk
List-Help: <mailto:dev-help@stdcxx.apache.org>
List-Unsubscribe: <mailto:dev-unsubscribe@stdcxx.apache.org>
List-Post: <mailto:dev@stdcxx.apache.org>
List-Id: <dev.stdcxx.apache.org>
Reply-To: dev@stdcxx.apache.org
Delivered-To: mailing list dev@stdcxx.apache.org
Received: (qmail 60491 invoked by uid 99); 2 Apr 2008 21:10:12 -0000
Received: from nike.apache.org (HELO nike.apache.org) (192.87.106.230)
    by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 02 Apr 2008 14:10:12 -0700
X-ASF-Spam-Status: No, hits=-0.0 required=10.0
	tests=SPF_PASS
X-Spam-Check-By: apache.org
Received-SPF: pass (nike.apache.org: local policy)
Received: from [208.30.140.160] (HELO moroha.roguewave.com) (208.30.140.160)
    by apache.org (qpsmtpd/0.29) with ESMTP; Wed, 02 Apr 2008 21:09:23 +0000
Received: from exchmail01.Blue.Roguewave.Com (exchmail01.blue.roguewave.com
 [10.22.129.22])
	by moroha.roguewave.com (8.13.6/8.13.6) with ESMTP id m32L9gQX024926
	for <dev@stdcxx.apache.org>; Wed, 2 Apr 2008 21:09:42 GMT
X-MimeOLE: Produced By Microsoft Exchange V6.5
Content-class: urn:content-classes:message
MIME-Version: 1.0
Content-Type: text/plain;
	charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
Subject: RE: [PATCH] STDCXX-423 LIMITS.cpp assumes integers with no padding
 bits
Date: Wed, 2 Apr 2008 15:09:55 -0600
Message-ID: 
 <CFFDD219128FD94FB4F92B99F52D0A4901708B9C@exchmail01.Blue.Roguewave.Com>
X-MS-Has-Attach: 
X-MS-TNEF-Correlator: 
Thread-Topic: [PATCH] STDCXX-423 LIMITS.cpp assumes integers with no padding
 bits
Thread-Index: AciMbwhDpNMTXVUDS5+YWFQO5v98agIlknlQ
References: 
 <CFFDD219128FD94FB4F92B99F52D0A499A2BC8@exchmail01.Blue.Roguewave.Com>
 <47E58C6D.6070204@roguewave.com>
From: "Scott Zhong" <Scott.Zhong@roguewave.com>
To: <dev@stdcxx.apache.org>
X-Virus-Checked: Checked by ClamAV on apache.org



> -----Original Message-----
> From: Martin Sebor [mailto:msebor@gmail.com] On Behalf Of Martin Sebor
> Sent: Saturday, March 22, 2008 4:47 PM
> To: dev@stdcxx.apache.org
> Subject: Re: [PATCH] STDCXX-423 LIMITS.cpp assumes integers with no
> padding bits
>=20
> Sorry Scott, I'm still not sure this is completely correct.
>=20
> According to 7.18.1.1 of C99, "The typedef name intN_t designates
> a signed integer type with width N, no padding bits, and a two's
> complement representation."
>=20
> Can you point me to the part of the patch that checks that each
> of the exact-width types has no padding bits and that it uses
> a two's complement representation?
>=20
> A few more comments are inline...
>=20
> Scott Zhong wrote:
> > Index: LIMITS.cpp
> > =
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> > --- LIMITS.cpp  (revision 638996)
> > +++ LIMITS.cpp  (working copy)
> > @@ -223,7 +223,19 @@
> >      return bits;
> >  }
> >
> > +template <class T>
> > +unsigned compute_type_bits()
> > +{
> > +    T max =3D T (one);
> > +    T current =3D T(one);
> > +    int bits =3D 1;
> >
> > +    for (; T (current * 2) > max; current *=3D2, max *=3D 2, =
bits++) {
}
> > +
> > +    return bits;
> > +}
>=20
> This function computes the number of bits in the value representation
> of the type T. We also need to compute the number of bits in the
object
> representation of the type (i.e., sizeof(T) * CHAR_BIT). Only if the
> two match, and when (no_twos_complement =3D=3D 0) holds can we define
> the exact-width types.
>=20
> > +
> > +
> >  // used to compute the size of a pointer to a member function
> >  struct EmptyStruct { };
> >
> > @@ -397,6 +409,12 @@
> >      // 1 for a 16-bit integer, etc)
> >      int width_bits =3D 0;
> >
> > +    // store exact bit size of each type
> > +    int ushort_bits =3D compute_type_bits<unsigned short> ();
> > +    int uint_bits =3D compute_type_bits<unsigned int> ();
> > +    int ulong_bits =3D compute_type_bits<unsigned long> ();
> > +    int ullong_bits =3D compute_type_bits<unsigned LLong> ();
>=20
> The last line needs to be guarded in case long long is not
> recognized as a type (e.g., EDG eccp in strict mode).
>=20
> Martin
>=20

Martin, the macro LLong already takes care of this.