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Date:      Fri, 31 Oct 2003 18:20:17 +0100
From:      Stefan Farfeleder <stefan@fafoe.narf.at>
To:        Erik Trulsson <ertr1013@student.uu.se>
Cc:        Garrett Wollman <wollman@khavrinen.lcs.mit.edu>
Subject:   Re: Anyone object to the following change in libc?
Message-ID:  <20031031172015.GD866@wombat.fafoe.narf.at>
In-Reply-To: <20031031154337.GA19287@falcon.midgard.homeip.net>
References:  <BAEB9CED-091F-11D8-B483-000393BB9222@queasyweasel.com> <3F9F4FE6.29C4E178@mindspring.com> <3FA0EEFD.431DD759@mindspring.com> <20031030120925.K80335@beagle.fokus.fraunhofer.de> <200310301659.h9UGxAPk023337@khavrinen.lcs.mit.edu> <20031031174658.T3463@gamplex.bde.org> <200310311506.h9VF6h8T030897@khavrinen.lcs.mit.edu> <20031031154337.GA19287@falcon.midgard.homeip.net>

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On Fri, Oct 31, 2003 at 04:43:37PM +0100, Erik Trulsson wrote:

> Perhaps not smaller in terms of the sizeof operator, but why can't one
> have a 16-bit char, and an int8_t which occupies 16 bits, but only uses
> 8 of them - the other 8 being padding?

7.18.1.1 Exact-width integer types

1 The typedef name intN_t designates a signed integer type with width N, no padding
  bits, and a two's complement representation. Thus, int8_t denotes a signed integer
  type with a width of exactly 8 bits.

> Where in C99 does it say that uint8_t can't have padding bits?
> I can't find anything in n869.txt to that effect.
> As far as I can tell, the only type that is not allowed to have any
> padding bits or trap representations is unsigned char.

uint8_t is int8_t's corresponding unsigned type.  This means
sizeof(uint8_t) == sizeof(int8_t), thus uint8_t can't have padding bits
either.

Cheers,
Stefan



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