[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);
}