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Re: base64.? going into rfc3548bis

From: Simon Josefsson
Subject: Re: base64.? going into rfc3548bis
Date: Tue, 28 Mar 2006 11:47:07 +0200
User-agent: Gnus/5.110004 (No Gnus v0.4) Emacs/22.0.50 (gnu/linux)

Paul Eggert <address@hidden> writes:

> Simon Josefsson <address@hidden> writes:
>> Alternatively, the prototype could be 'void*' for the data and cast it
>> to 'uint8_t*' internally.  That would be safe, wouldn't it?
> No, because C implementations need not support uint8_t.  It is an
> optional type.

Even in C99?  The code assume C99 already (stdbool.h).

> Come to think of it, even 'char *' might have problems, since the
> value (char) 0x80 might be a 'trap representation', which causes
> undefined behavior if you try to use it.

Do you have a reference for this?  Is it enough to cast it to unsigned
char whenever you actually dereference it?

> So you may need to change the interface to use 'unsigned char *'
> instead.  The C Standard says that 'unsigned char' is safe; it cannot
> possibly have a trap representation.
> But all this is relevant only if you want the code to be portable to
> hosts where CHAR_BIT is not 8, or which do not use two's complement.
> For sanity's sake, you may be better on insisting that CHAR_BIT is 8,
> and on using unsigned char so that UCHAR_MAX must be 255.  That's good
> enough for an RFC, I think.

Hm, I'd like to avoid 'unsigned char*' if possible, having explicit
signed and unsigned seems to generate a lot of warnings.


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