On 5/4/20 4:26 PM, Philippe Mathieu-Daudé wrote:
> When building with Clang 10 on Fedora 32, we get:
>
> tests/qht-bench.c:287:29: error: implicit conversion from 'unsigned long' to 'double' changes value from 18446744073709551615 to 18446744073709551616 [-Werror,-Wimplicit-int-float-conversion]
> *threshold = rate * UINT64_MAX;
> ~ ^~~~~~~~~~
> /usr/include/stdint.h:130:23: note: expanded from macro 'UINT64_MAX'
> # define UINT64_MAX (__UINT64_C(18446744073709551615))
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> /usr/include/stdint.h:107:25: note: expanded from macro '__UINT64_C'
> # define __UINT64_C(c) c ## UL
> ^~~~~~~
> <scratch space>:14:1: note: expanded from here
> 18446744073709551615UL
> ^~~~~~~~~~~~~~~~~~~~~~
>
> Fix by using nextafter() from <math.h>:
>
> float nextafterf( float from, float to );
>
> Returns the next representable value of 'from'
> in the direction of 'to'.
>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
> Cc: Emilio G. Cota <cota@braap.org>
> Cc: Alex Bennée <alex.bennee@linaro.org>
> Cc: Richard Henderson <richard.henderson@linaro.org>
> Cc: Alexander Bulekov <alxndr@bu.edu>
> ---
> tests/qht-bench.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/tests/qht-bench.c b/tests/qht-bench.c
> index e3b512f26f..f93f8e0fe2 100644
> --- a/tests/qht-bench.c
> +++ b/tests/qht-bench.c
> @@ -10,6 +10,7 @@
> #include "qemu/qht.h"
> #include "qemu/rcu.h"
> #include "qemu/xxhash.h"
> +#include <math.h>
>
> struct thread_stats {
> size_t rd;
> @@ -284,7 +285,7 @@ static void do_threshold(double rate, uint64_t *threshold)
> if (rate == 1.0) {
> *threshold = UINT64_MAX;
> } else {
> - *threshold = rate * UINT64_MAX;
> + *threshold = rate * nextafterf(0x1p64, 0.0);
NAck since of double type. Will send v2.
> }
> }
>
>