Re: [PATCH 7/16] Let void have sizeof 1

[Derek M Jones <derek@knosof.co.uk>]

Alexey,

>> In the Linux kernel, we've got lots of void * address arithmetics:
>> linux/linux-2.6$ make -j 8 CC='gcc -Wpointer-arith' 2>&1 | grep
>> 'warning: pointer of type \'void \*\' used in arithmetic' | uniq | wc
>> -l
>> 45095
> I screwed up, it should be | sort -u | uniq | wc -l
> But it's still 14488.

This is a sufficiently large number that we ought to consider adding
checks for the usage, for instance:

    1) Are the arguments really chars of one sort or another and
therefore the parameter ought to be declared as such?

    2) The arguments have various structure and/or array types and
the storage is being walked over in the called function.  Can the
minimum size ever passed be worked out and this information used in
the size_void (my proposed name for a pointer that has either sizeof,
++ or -- performed on it) function to check for overruns.

    3) Are there any restrictions on passing a void pointer to a
size_void function or vice versa?  I cannot think of any obvious
ones, but then I don't know the various kinds of circumstances
in which this happens.

    4) Other possible fault issues, people?

-- 
Derek M. Jones                         tel: +44 (0) 1252 520 667
Knowledge Software Ltd                 mailto:derek@knosof.co.uk
Source code analysis                   http://www.knosof.co.uk