Padding bits and char, unsigned char, signed char

[Ioannis Vranos]

Under C95:

Is it guaranteed that char, unsigned char, signed char have no padding bits?

[CBFalconer]

Ioannis Vranos wrote:

>
Under C95: Is it guaranteed that char, unsigned char, signed
char have no padding bits?

unsigned char, yes. The others by implication. I haven't checked
the standard. Why don't you?

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home.att.net>
Try the download section.

--
Posted via a free Usenet account from http://www.teranews.com

[Harald van =?UTF-8?b?RMSzaw==?=]

On Fri, 28 Mar 2008 16:01:54 -0500, CBFalconer wrote:

Ioannis Vranos wrote:

>Under C95: Is it guaranteed that char, unsigned char, signed char have
no padding bits?

Just a note: padding bits are a concept introduced in the standard in
C99; C90/C95 left much more unspecified about the representation of
integer types.

unsigned char, yes.

Where is this guarantee made? In C99, 5.2.4.2.1 makes it as clear as it
can: "The value UCHAR_MAX shall equal 2^CHAR_BIT - 1." I don't have a
copy of an older standard. Does it make the same guarantee?

The others by implication.

How so? What's preventing a signed integer type and its corresponding
unsigned type from having a different number of padding bits?

[pete]

Harald van =?UTF-8?b?RMSzaw==?= wrote:

>
On Fri, 28 Mar 2008 16:01:54 -0500, CBFalconer wrote:

Ioannis Vranos wrote:

Under C95: Is it guaranteed that char,
unsigned char, signed char have no padding bits?

Just a note: padding bits are a concept introduced in the standard in
C99; C90/C95 left much more unspecified about the representation of
integer types.

unsigned char, yes.

Where is this guarantee made?
In C99, 5.2.4.2.1 makes it as clear as it
can: "The value UCHAR_MAX shall equal 2^CHAR_BIT - 1." I don't have a
copy of an older standard. Does it make the same guarantee?

It doesn't.
There's really nothing about padding in the "basic types" in C90.

The others by implication.

How so? What's preventing a signed integer type and its corresponding
unsigned type from having a different number of padding bits?

I think he meant char and signed char, but even then I disagree.

As far as I know, signed char can have padding bits.

--
pete

[Ben Bacarisse]

Harald van Dijk <tr*****@gmail.comwrites:

On Fri, 28 Mar 2008 16:01:54 -0500, CBFalconer wrote:

>Ioannis Vranos wrote:

>>Under C95: Is it guaranteed that char, unsigned char, signed char have
no padding bits?

Just a note: padding bits are a concept introduced in the standard in
C99; C90/C95 left much more unspecified about the representation of
integer types.

>unsigned char, yes.

Where is this guarantee made? In C99, 5.2.4.2.1 makes it as clear as it
can: "The value UCHAR_MAX shall equal 2^CHAR_BIT - 1."

But that alone is not enough, is it? The clearest statement comes
later in 6.2.6. p1: "For unsigned integer types other than unsigned
char, the bits of the object representation shall be divided into two
groups: value bits and padding bits (there need not be any of the
latter).". So, unsigned char has only value bits.

--
Ben.