Re: Memory protection between compilation units?

antispam@fricas.org (Waldek Hebisch) writes:

Mateusz Viste <mateusz@not.gonna.tell> wrote:
>

That said, detecting out-of-bounds array access is no panacea.  Memory
corruption can arise from various sources, such as dangling pointers or
poorly managed pointer arithmetic.

>
AFAICS there is no reason for explicit pointer arithmetic in well
written C programs.

This assertion is in effect a No True Scotsman statement.

Implicit pointer arithmetic (coming from array
indexing) is done by compiler so should be no problem.

Even if there is no direct manipulation ("pointer arithmetic") of
pointer variables, access can be checked only if array bounds
information is available, and in many cases it isn't.  The reason is
(among other things) C doesn't have array parameters;  what it does
have instead is pointer parameters.  At the point in the code when
an "array" access is to be done, the information needed to check
that an index value is in bounds just isn't available.  The culprit
here is not explicit pointer arithmetic, but lacking the information
needed to do a bounds check.  That lack is inherent in how the C
language works with respect to arrays and pointer conversion.