• bearophile (22/22) Dec 24 2011 C1X (C11), the successor of C99, is now designed, among its changes ther...
• Vladimir Panteleev (2/6) Dec 24 2011 How about: scope(success) assert(0); ?
• Andrei Alexandrescu (6/12) Dec 24 2011 The attribute should be migrated to the signature of the function such
• Jonathan M Davis (10/24) Dec 25 2011 It's the sort of thing that we could add at any time without breaking
• Caligo (3/6) Dec 24 2011 Functions are like people. Sometimes they go places that's so beautiful

bearophile <bearophileHUGS lycos.com> writes:

C1X (C11), the successor of C99, is now designed, among its changes there is
_Noreturn, this is what the latest free draft says about it:

A function declared with a _Noreturn function specifier shall not return to its
caller.
The implementation should produce a diagnostic message for a function declared
with a _Noreturn function specifier that appears to be capable of returning to
its caller.


_Noreturn void f () {
    abort(); // ok
}
_Noreturn void g (int i) { // causes undefined behavior if i<=0
    if (i > 0) abort();
}



#include <setjmp.h>
_Noreturn void longjmp(jmp_buf env, int val);


#include <stdlib.h>
_Noreturn void abort(void);


#include <stdlib.h>
_Noreturn void exit(int status);


#include <stdlib.h>
_Noreturn void _Exit(int status);


#include <stdlib.h>
_Noreturn void quick_exit(int status);

GNU C has a noreturn attribute since a lot of time. I don't fully understand
why such attribute is so useful in C programs, but is something like a
 noreturn function attribute useful in D too? Maybe to implement a better halt
assert(0)?

Bye,
bearophile

"Vladimir Panteleev" <vladimir thecybershadow.net> writes:

On Saturday, 24 December 2011 at 20:09:46 UTC, bearophile wrote:
 GNU C has a noreturn attribute since a lot of time. I don't 
 fully understand why such attribute is so useful in C programs, 
 but is something like a  noreturn function attribute useful in 
 D too? Maybe to implement a better halt assert(0)?

How about: scope(success) assert(0); ?

Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:

On 12/24/2011 06:58 PM, Vladimir Panteleev wrote:
 On Saturday, 24 December 2011 at 20:09:46 UTC, bearophile wrote:
 GNU C has a noreturn attribute since a lot of time. I don't fully
 understand why such attribute is so useful in C programs, but is
 something like a  noreturn function attribute useful in D too? Maybe
 to implement a better halt assert(0)?

 How about: scope(success) assert(0); ?

The attribute should be migrated to the signature of the function such 
that calling code can take advantage of it.

I personally think this is a small matter. Right now we have bigger 
rocks to move. It would be great if 2.058 had all [tdpl] bugs fixed.


Andrei

"Jonathan M Davis" <jmdavisProg gmx.com> writes:

On Saturday, December 24, 2011 22:26:02 Andrei Alexandrescu wrote:
 On 12/24/2011 06:58 PM, Vladimir Panteleev wrote:
 On Saturday, 24 December 2011 at 20:09:46 UTC, bearophile wrote:
 GNU C has a noreturn attribute since a lot of time. I don't fully
 understand why such attribute is so useful in C programs, but is
 something like a  noreturn function attribute useful in D too? Maybe
 to implement a better halt assert(0)?

 
 How about: scope(success) assert(0); ?

 
 The attribute should be migrated to the signature of the function such
 that calling code can take advantage of it.
 
 I personally think this is a small matter. Right now we have bigger
 rocks to move. It would be great if 2.058 had all [tdpl] bugs fixed.

It's the sort of thing that we could add at any time without breaking 
backwards compatibility, so there's no rush unless it solves a burning 
problem. But at best, it solves a minor inconvenience. Solving the TDPL on the 
other hand would resolve a major usability issue for the language - 
particularly how it affects newbies reading TDPL. But completely aside from the 
newbies, it's a major milestone in actually having the full language 
implemented so that there's a lot less of a distinction between the design and 
the implementation.

- Jonathan M Davis

Caligo <iteronvexor gmail.com> writes:

On Sat, Dec 24, 2011 at 2:09 PM, bearophile <bearophileHUGS lycos.com>wrote:

 I don't fully understand why such attribute is so useful in C programs

 Bye,
 bearophile

Functions are like people.  Sometimes they go places that's so beautiful
that they never want to return.