Re: Supporting byte-addressability on word-addressed hardware

>[Pointer representations for GNU CC]


There are a variety of C compilers that use more than one pointer
format. For example, the DEC-20 KCC-20 used *four* pointer formats.


Multiple pointer formats can lead to problems with some C code that is
nonportable, but common nonetheless. For example, the following code
is nonportable and fails:


int *p = malloc (sizeof(int));
free (p);


The correct solution is to cast `p' to a `char *' before passing it to
`free'. However, you might be unwilling to do this (or force your
users to do this) and failing to use the casts can lead to mysterious
failures. Your call.


FWIW, a number of such issues are discussed in the `Portability'
section of ``Recommended C Style and Coding Standards'' by a long list
of authors including me. The document is available via WWW URL,
anonymous ftp, and printed on paper


http://www.cs.washington.edu/homes/pardo/papers.d/cstyle.html
ftp://ftp.cs.washington.edu/pub/pardo/cstyle.ps.Z
ftp://ftp.cs.washington.edu/pub/cstyle.tar.Z (source)
sales@ssc.com (paper)


Grungier details, such as the pointer format stuff is discussed in the
troff source comments (sorry!).


;-D on ( Answers to questions you didn't think you asked ) Pardo
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