qht: Fix threshold rate calculation

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;
                          ~ ^~~~~~~~~~

Fix this by splitting the 64-bit constant into two halves,
each of which is individually perfectly representable, the
sum of which produces the correct arithmetic result.

This is very likely just a sticking plaster over some underlying
incorrect code, but it will suppress the warning for the moment.

Cc: Emilio G. Cota <cota@braap.org>
Reported-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

diff --git a/tests/qht-bench.c b/tests/qht-bench.c
index e3b512f26f376e3b145bc716af5276424b394d18..eb88a90137611690e89b07501d3784dfe97d01a7 100644 (file)
--- a/tests/qht-bench.c
+++ b/tests/qht-bench.c
@@ -284,7 +284,8 @@ static void do_threshold(double rate, uint64_t *threshold)
     if (rate == 1.0) {
         *threshold = UINT64_MAX;
     } else {
-        *threshold = rate * UINT64_MAX;
+        *threshold = (rate * 0xffff000000000000ull)
+                   + (rate * 0x0000ffffffffffffull);
     }
 }