level of questions for experts only

[ROSY]

hello,
response if u ,on all level of questions:::
1.how a self deletable .exe file deleted on some future date & time
without
invoking the .exe itself?
2.if we want that any wildcard characters in command line arguments
should be appropriately expanded,are we reqd. 2 make any special
provision?if yes,which?
3.why :: printf("%%%%%") ; output %%%.
4.how 2 run a .obj file without previously creating any .exe?
5.what is classical class?(FOR C++)

bye,

[Arthur J. O'Dwyer]

On Tue, 30 Sep 2003, Dan Pop wrote:

Peter Nilsson writes:

Arthur J. O'Dwyer wrote...

"C programs" with constraint violations: do not compile,
[because producing a diagnostic doesn't guarantee anything
about the contents of any executable that might be produced]
thus are not *really* written in C.<sigh>

You'll have to define what YOU mean by a "real" C program.

That's easy: a program that doesn't require any diagnostic and that
doesn't invoke any form of undefined behaviour that can be detected at
translation time.

I must here disagree with Dan; I'd rather keep my definition,
because the concept of "UB that can be detected at translation time"
is almost certainly not well-defined. OTOH, the Standard quite
*clearly* defines what it means by "constraint violation" (as far
as I can tell), so it's quite obvious whether any particular
program contains a constraint violation or not.

I would call code demonstrating UB a "bad C program" -- but still
a C program, just one without well-defined results when executed.
In other words, it's a C program which is *not* a *correct* C
program, as you say below.
I prefer the term "correct C program", as defined by C99, which
is a bit more restrictive.

True. I bet that determining whether a given program is correct
given only its source code is undecidable, though, so that's not
a very good definition for use by compilers. :-)

-Arthur

[Chris Dollin]

ROSY wrote:

response if u ,on all level of questions:::
I am not a comma.
1.how a self deletable .exe file deleted on some future date & time
without
invoking the .exe itself?
This is not a C question.
2.if we want that any wildcard characters in command line arguments
should be appropriately expanded,are we reqd. 2 make any special
provision?if yes,which?
This is not an implementation-independant C question.
3.why :: printf("%%%%%") ; output %%%.
Probably a bug in the run-time support.
4.how 2 run a .obj file without previously creating any .exe?
This is not a C question.
5.what is classical class?(FOR C++)

This is not a C question, and it's not a C++ question either, but
one answer is, it's a class for the teaching of classics.

Why not post non-C questions to non-C newsgroups ... *please*?

--
Chris "progressive rock hedgehog" Dollin
C FAQs at: http://www.faqs.org/faqs/by-newsgrou...mp.lang.c.html
C welcome: http://www.angelfire.com/ms3/bchambl...me_to_clc.html

[Peter Nilsson]

Richard Heathfield <do******@address.co.uk.invalid> wrote in message news:<bl**********@sparta.btinternet.com>...

Peter Nilsson wrote:

"Arthur J. O'Dwyer" <aj*@nospam.andrew.cmu.edu> wrote in message
news:<Pi**********************************@unix46. andrew.cmu.edu>...

"C programs" with constraint violations: do not compile,

Chapter and Verse please.

Every one of my compilers successfully translates...

unsigned char *p = 0xFFFE;

The #error directive (not excluded by #if) is the *only* construct in
which an implementation *must* fail to translate a program.

I'm not convinced that the implementation /must/ fail to translate a program
under this circumstance. Do you have C&V?

C99 4p4:

The implementation shall not successfully translate a preprocessing
translation unit containing a #error preprocessing directive unless
it is part of a group skipped by conditional inclusion.

--
Peter

[Dave Thompson]

On Sun, 28 Sep 2003 19:46:01 +0100, Mark Gordon
<sp******@flash-gordon.me.uk> wrote:

On Sun, 28 Sep 2003 12:51:19 -0400 (EDT)
"Arthur J. O'Dwyer" <aj*@nospam.andrew.cmu.edu> wrote:

<snip>

int array[1], *pointer = (char*)array;

Sorry, pete, I don't get it. Is the above undefined or
incorrect in some way?

array is an array of ints which is being cast to a char*
*pointer is a pointer to an int which is having a pointer to char
assigned to it.

IIRC you are not allowed to assign a pointer to char to another pointer
type without a cast and I don't think the conversion from int* -> char*
-> int* is guaranteed.

Correct you can't implicitly convert, and hence assign, pass, return,
or initialize without cast, char* to any other data pointer *except*
void*. (Plus qualification as needed; that's orthogonal to type.)

With cast, the result is guaranteed for char (or void). 6.3.2.3p7:
A pointer to an object or incomplete type may be converted to a
pointer to a different
object or incomplete type. If the resulting pointer is not correctly
aligned57) for the
pointed-to type, the behavior is undefined. Otherwise, when converted
back again, the
result shall compare equal to the original pointer. <snip>

Plus the fact that every object (hence every valid object pointer)
must be sufficiently aligned for character types (and void pointers),
but this is not required for any other data type. And that nonnull
data pointers compare equal iff they point to the same object, or the
special and problematic case &just_past_a == &b, but that shouldn't
apply here.

- David.Thompson1 at worldnet.att.net