assert warn side effects (recent clangs)

assert.c

// See in action https://godbolt.org/z/eYon5nWrP

extern void __assert_fn(void);

#define assert(e)   do { if (!(e)) { __builtin_assume(!(e)); __assert_fn(); } } while (0);

static inline int nonpure_fn(void)
{
    return 0;
}

__attribute__((pure))
static inline int pure_fn(void)
{
    return 0;
}

__attribute__((const))
static inline int const_fn(void)
{
    return 0;
}


void foo(void)
{
    int a = 0;
    int b = 0;

    assert(1);
    assert(2 + 1);
    assert(a + 1);

    assert(a = b); // warn here
    assert(a++);  // warn here

    assert(nonpure_fn()); // warn here
    assert(pure_fn());
    assert(const_fn());
}