[Bug c/61985] New: It's possible to declare a function pointer as noreturn using the old volatile syntax but not normally.

[Bug c/61985] New: It's possible to declare a function pointer as noreturn using the old volatile syntax but not normally.

[sstewartgallus00 at mylangara dot bc.ca]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61985

            Bug ID: 61985
           Summary: It's possible to declare a function pointer as
                    noreturn using the old volatile syntax but not
                    normally.
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sstewartgallus00 at mylangara dot bc.ca

It's against the C11 standard to let people use the _Noreturn keyword on a
function pointer type. It's treated the same as the inline keyword. In my
opinion this is silly but whatever. Anyways, it is possible to declare a
function pointer as noreturn using the old volatile syntax but not using the
noreturn keyword or attribute. Eg)

#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdnoreturn.h>

typedef void f(void * restrict, int);
typedef volatile f next_t;

__attribute__((noinline)) noreturn void increment(void * restrict context,
                                                  next_t * next,
                                                  int xx)
{
    next(context, xx + 1);
}

__attribute__((noinline)) noreturn void main_1(void * restrict context, int
xx);
__attribute__((noinline)) noreturn void main_2(void * restrict context, int
xx);


int main(void)
{
    {
        int value = 4;
        printf("value: %i\n", value);

        increment(NULL, main_1, value);
    }
}

__attribute__((noinline)) noreturn void main_1(void * restrict context, int xx)
{
    printf("value + 1: %i\n", xx);

    increment(NULL, main_2, xx);
}

__attribute__((noinline)) noreturn void main_2(void * restrict context, int xx)
{
    printf("value + 2: %i\n", xx);

    exit(EXIT_FAILURE);
}

[Bug c/61985] It's possible to declare a function pointer as noreturn using the old volatile syntax but not normally.

[joseph at codesourcery dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61985

--- Comment #1 from joseph at codesourcery dot com <joseph at codesourcery dot com> ---
I'm afraid I can't tell what you think the bug here is.  You make a true 
statement about C11 - that's not a bug report.  You give some C code - 
that's not a bug report either.  You don't say what GCC version or 
command-line options you use with the C code, or what you think GCC is 
doing wrong with that code, why you think that is wrong and what you think 
it should do instead.

[Bug c/61985] It's possible to declare a function pointer as noreturn using the old volatile syntax but not normally.

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61985

Marek Polacek <mpolacek at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
                 CC|                            |mpolacek at gcc dot gnu.org
         Resolution|---                         |INVALID

--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
The reporter seems to complain that it is not possible to declare a function
pointer as noreturn using the noreturn keyword or attribute.  But the attribute
should work:

__attribute__ ((__noreturn__)) void (*fp1) (void); // OK
_Noreturn void (*fp2) (void); // invalid

You only have to be careful that if you include <stdnoreturn.h>, the "noreturn"
gets expanded to _Noreturn, so you'd get "attribute directive ignored".