Safe subset of C?

[Robert Vazan]

I am looking for other people's attempts to create safe subset of C and
enforce it with scripts. Does anybody know about anything like this?

By "safe", I mean the following:
* Strongly typed memory. No way to reinterpret it as bunch of bytes
* Recovery from invalid and NULL pointers other than crash
* Possibility to isolate piece of code by not giving it key pointers

Library used to support such safe subset must not introduce its own flaws.
For example, it is not a good idea to use int proxies for pointers like
Unix API does, because this allows pointer guessing and consequently
prevents isolation.

[Alex]

Christian Bau <ch***********@ cbau.freeserve. co.uk> wrote:

In article <pa************ *************** *@lightspeed.bc .ca>,
Kelsey Bjarnason <ke*****@lights peed.bc.ca> wrote:

On Mon, 24 Nov 2003 19:06:16 +0100, Robert Vazan wrote:

> On Sun, 23 Nov 2003 19:17:27 -0500, Sheldon Simms wrote:
>
>> I guess you figure that all those "smart programmers" are incapable of
>> using any other language.
>
> I didn't want to offend you. I am also capable of using other languages,
> but I have got very sensitive to quality of tools and I am consequently
> very sceptical about any new language.
>
>> I can't speak for anyone else, but I wouldn't be
>> interested in working in crippled C.
>
> So you compile with warnings turned off?

Having warnings enabled doesn't cripple C; it just lets you know when
you've done something that probably isn't actually C at all. :)

If it isn't C at all you would get an error. If you get a warning, it's
most likely perfectly legal C that in some non-obvious way does
something entirely different from what you intended.

AFAIK "diagnostic s" need only be output from the compiler,
not specifically as "errors" or "warnings".

Alex

[Sheldon Simms]

On Tue, 25 Nov 2003 18:14:22 +0100, Robert Vazan wrote:

On Mon, 24 Nov 2003 15:29:41 -0500, Sheldon Simms wrote:

Warnings don't prevent me from doing anything, and lots of things

You can get warning that not all members of enum are enumerated in switch
statement. You can get warning about missing return statement even if you
know that end of function is unreachable.

Indeed. How is C crippled by such warnings?

that you want to disallow, such as treating any object as an array of
bytes, can be done perfectly safely and portably.

The only thing that you can do portably is copying those bytes to new
location. Reflection and metadata can do much more and they are type-safe.

What does that have to do with C?

[Kelsey Bjarnason]

[snips]

On Tue, 25 Nov 2003 07:58:14 +0000, Christian Bau wrote:

Having warnings enabled doesn't cripple C; it just lets you know when
you've done something that probably isn't actually C at all. :)

If it isn't C at all you would get an error.

Really? Hmm.

[kelseyb@baldur]$ gcc test.c
test.c: In function `main':
test.c:3: warning: `return' with a value, in function returning void
test.c:2: warning: return type of `main' is not `int'

The code:

void main()
{
return 0;
}
Seems I get a warning, not an error with warnings enabled. So, you're
suggesting that void main() is, in fact, C? As I recall, the standards
explicitly state that main returns int, not void, not double, not pointer
to char, but int, and anything else ain't C.

[James Hu]

On 2003-11-25, Robert Vazan <ro*********@pr ivateweb.sk> wrote:

On Tue, 25 Nov 2003 01:01:10 -0600, James Hu wrote:

There are already tools that do this. A web search for memory
debugging tools will provide many hits.

They aren't suitable for release code. And even in debug code, they crash
the program. It's just that they crash it near to point of error.

Not all of them behave as you describe. I am offering you the
suggestion to encourage you to not re-invent the wheel.

-- James

[Joona I Palaste]

Alex <al*******@hotm ail.com> scribbled the following:

Christian Bau <ch***********@ cbau.freeserve. co.uk> wrote:

In article <pa************ *************** *@lightspeed.bc .ca>,
Kelsey Bjarnason <ke*****@lights peed.bc.ca> wrote:

Having warnings enabled doesn't cripple C; it just lets you know when
you've done something that probably isn't actually C at all. :)

If it isn't C at all you would get an error. If you get a warning, it's
most likely perfectly legal C that in some non-obvious way does
something entirely different from what you intended.

AFAIK "diagnostic s" need only be output from the compiler,
not specifically as "errors" or "warnings".

So does this:

"ISO says I have to issue a diagnostic here. So to keep them happy I'll
do so."

qualify as a mandatory diagnostic for a case for which the ISO C
standard mandates one?

--
/-- Joona Palaste (pa*****@cc.hel sinki.fi) ------------- Finland --------\
\-- http://www.helsinki.fi/~palaste --------------------- rules! --------/
"To err is human. To really louse things up takes a computer."
- Anon

[Dave Vandervies]

In article <br**********@o ravannahka.hels inki.fi>,
Joona I Palaste <pa*****@cc.hel sinki.fi> wrote:

Alex <al*******@hotm ail.com> scribbled the following:

Christian Bau <ch***********@ cbau.freeserve. co.uk> wrote:

If it isn't C at all you would get an error. If you get a warning, it's
most likely perfectly legal C that in some non-obvious way does
something entirely different from what you intended.

AFAIK "diagnostic s" need only be output from the compiler,
not specifically as "errors" or "warnings".

So does this:

"ISO says I have to issue a diagnostic here. So to keep them happy I'll
do so."

qualify as a mandatory diagnostic for a case for which the ISO C
standard mandates one?

Wouldn't that depend on whether it's documented by the compiler as
a diagnostic?

Perhaps a better wording would be "...So to keep them happy I'm doing
so.". That way it's clear from the message that it is in fact the
required diagnostic.
dave
(In a pedantic mood today, it seems. Not that that's a Bad Thing.)

--
Dave Vandervies dj******@csclub .uwaterloo.ca
[W]hen I am among non-physician Ph.D.s who go by "Doctor" then I like
to be called "Bachelor Petrofsky" in honor of my B.S..
--Al Petrofsky in comp.lang.schem e

[Alex]

Joona I Palaste <pa*****@cc.hel sinki.fi> wrote:

Alex <al*******@hotm ail.com> scribbled the following:

Christian Bau <ch***********@ cbau.freeserve. co.uk> wrote:

In article <pa************ *************** *@lightspeed.bc .ca>,
Kelsey Bjarnason <ke*****@lights peed.bc.ca> wrote:
Having warnings enabled doesn't cripple C; it just lets you know when
you've done something that probably isn't actually C at all. :) If it isn't C at all you would get an error. If you get a warning, it's
most likely perfectly legal C that in some non-obvious way does
something entirely different from what you intended.

AFAIK "diagnostic s" need only be output from the compiler,
not specifically as "errors" or "warnings".

So does this: "ISO says I have to issue a diagnostic here. So to keep them happy I'll
do so." qualify as a mandatory diagnostic for a case for which the ISO C
standard mandates one?

Sure. The extent of the diagnostic is not defined. It is a QoI
issue.

Alex