Re: pgsql: Test pg_atomic_fetch_add_ with variable addend and 16-bitedge c

Hi,

On 2019-09-15 15:14:50 -0700, Noah Misch wrote:
> On Sun, Sep 15, 2019 at 01:00:21PM -0300, Alvaro Herrera wrote:
> > On 2019-Sep-14, Noah Misch wrote:
> > > Test pg_atomic_fetch_add_ with variable addend and 16-bit edge cases.
> > 
> > I don't understand this.
> > 
> >     if (pg_atomic_fetch_add_u32(&var, INT_MAX) != INT_MAX)
> >         elog(ERROR, "pg_atomic_add_fetch_u32() #3 wrong");
> > 
> >     pg_atomic_fetch_add_u32(&var, 2);   /* wrap to 0 */
> > 
> >     if (pg_atomic_fetch_add_u32(&var, PG_INT16_MAX) != 0)
> >         elog(ERROR, "pg_atomic_fetch_add_u32() #3 wrong");
> > 
> > The existing one seems to be naming the wrong function in the error
> > message, and if you fix that then you have two "#3 wrong" cases.
> > Isn't this confusing?  Am I just too sensitive?  Is this pointless to
> > fix?
> 
> It's a typo-class defect.  Would you like me to fix it, or would you like to
> fix it?  I'd consider wrapping the tests in a macro (may be overkill, since
> these tests don't change much):
> 
> --- a/src/test/regress/regress.c
> +++ b/src/test/regress/regress.c
> @@ -670,6 +670,16 @@ test_atomic_flag(void)
>      pg_atomic_clear_flag(&flag);
>  }
>  
> +#define EXPECT(result_expr, expected_expr)        \
> +    do { \
> +        uint32        result = (result_expr); \
> +        uint32        expected = (expected_expr); \
> +        if (result != expected) \
> +            elog(ERROR, \
> +                 "%s yielded %u, expected %s in file \"%s\" line %u", \
> +                 #result_expr, result, #expected_expr, __FILE__, __LINE__); \
> +    } while (0)
> +

While it might be overkill on its own, it seems like it'd be a good
utility to have for these kinds of tests.

Unfortunately we can't easily make this type independent. The local
variables are needed to avoid multiple evaluation. While we could infer
their type using compiler specific magic (__typeof__() or C++), we'd
still need to print them.  We could however remove the local variables,
and purely rely on stringification of the arguments for printing the
error.


>  static void
>  test_atomic_uint32(void)
>  {
> @@ -678,17 +688,10 @@ test_atomic_uint32(void)
>      int            i;
>  
>      pg_atomic_init_u32(&var, 0);
> -
> -    if (pg_atomic_read_u32(&var) != 0)
> -        elog(ERROR, "atomic_read_u32() #1 wrong");
> -
> +    EXPECT(pg_atomic_read_u32(&var), 0);
>      pg_atomic_write_u32(&var, 3);
> -
> -    if (pg_atomic_read_u32(&var) != 3)
> -        elog(ERROR, "atomic_read_u32() #2 wrong");
> -
> -    if (pg_atomic_fetch_add_u32(&var, pg_atomic_read_u32(&var) - 2) != 3)
> -        elog(ERROR, "atomic_fetch_add_u32() #1 wrong");
> +    EXPECT(pg_atomic_read_u32(&var), 3);
> +    EXPECT(pg_atomic_fetch_add_u32(&var, pg_atomic_read_u32(&var) - 2), 3);
>  
>      if (pg_atomic_fetch_sub_u32(&var, 1) != 4)
>          elog(ERROR, "atomic_fetch_sub_u32() #1 wrong");

I'd name it EXPECT_EQ_U32 or such, but otherwise I think this is a clear
improvement.

Greetings,

Andres Freund