On 04/10/2018 10:56, Jonathan Wakely wrote:
On Thu, 4 Oct 2018 at 09:51, Sebastian Huber wrote:
Hello,
I use a typedef for static assertions for pre C11 compilers. For one
static assertion
typedef struct { int i; } sem_t;
typedef int static_assert_sem_failed [((void *)0 == (sem_t *)0) ? 1 : -1];
_Static_assert((void *)0 == (sem_t *)0, "sem_failed");
I get a warning like this:
gcc -S -o - sa.c > /dev/null
sa.c:3:1: warning: variably modified ‘static_assert_sem_failed’ at file
scope
typedef int static_assert_sem_failed [((void *)0 == (sem_t *)0) ? 1 : -1];
^~~~~~~
Is there some way to get around this warning?
You could move the homemade assertion so it's not at file scope:
__attribute__((used)) static void assertions() {
__attribute__((used)) typedef int static_assert_sem_failed [((void
*)0 == (sem_t *)0) ? 1 : -1];
}
Thanks, this works.
The same expression in the
_Static_assert() doen't lead to a warning.
It does with -pedantic, and that makes the reason for the warning clearer:
foo.c:5:26: warning: expression in static assertion is not an integer
constant expression [-Wpedantic]
_Static_assert((void *)0 == (sem_t *)0, "sem_failed");
This looks bad, so basically a pointer constant doesn't exist in standard C?
--
Sebastian Huber, embedded brains GmbH
Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone : +49 89 189 47 41-16
Fax : +49 89 189 47 41-09
E-Mail : sebastian.huber@xxxxxxxxxxxxxxxxxx
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