Re: [Tinycc-devel] Bounds checking not working?

[grischka]

Arnold Meijster wrote:
> I will be teaching a course in C programming at the university
> and was looking for a C compiler/interpreter that does 
> bound checking (for first year's students that seems to be a good idea).
> After some googling, I found tcc. It seems to be perfect for what I 
> want, ...

Disclaimer: TCC's bound checking is not well tested and also the
algorithm is probably flawed in some aspects.  It should work for
simple cases though.

> [...]
> As you can see, the boundschecking version is somewhat different; it
> crashes instead of running on without any error (as without checking).
> However, I don't think this is the behaviour to be expected, or is it?

Is expected. See lib/bcheck.c:

    /* print a bound error message */
    static void bound_error(const char *fmt, ...)
    {
        __bound_error_msg = fmt;
        *(int *)0 = 0; /* force a runtime error */
    }

Basically "-b" is meant to be used with "-run" where tcc prints
"__bound_error_msg" from its built-in exception handler:

    $ tcc -b -run outofbound.c

You can also try the "btest" example, which runs the snippets in
tests/boundtest.c:

    $ make -C tests btest

--- grischka