[PATCH v4 5/6] mempool: avoid floating point expression in static assertion

[Stephen Hemminger <stephen@networkplumber.org>]

Clang does not handle casts in static_assert() expressions.
It doesn't like use of floating point to calculate threshold.
Use a different expression with same effect.

Modify comment in mlx5 so that developers don't go searching
for old value.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 drivers/net/mlx5/mlx5_rxq.c | 2 +-
 lib/mempool/rte_mempool.c   | 7 ++++---
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/net/mlx5/mlx5_rxq.c b/drivers/net/mlx5/mlx5_rxq.c
index 1bb036afebb3..7d972b6d927c 100644
--- a/drivers/net/mlx5/mlx5_rxq.c
+++ b/drivers/net/mlx5/mlx5_rxq.c
@@ -1444,7 +1444,7 @@ mlx5_mprq_alloc_mp(struct rte_eth_dev *dev)
 	/*
 	 * rte_mempool_create_empty() has sanity check to refuse large cache
 	 * size compared to the number of elements.
-	 * CACHE_FLUSHTHRESH_MULTIPLIER is defined in a C file, so using a
+	 * CALC_CACHE_FLUSHTHRESH() is defined in a C file, so using a
 	 * constant number 2 instead.
 	 */
 	obj_num = RTE_MAX(obj_num, MLX5_MPRQ_MP_CACHE_SZ * 2);
diff --git a/lib/mempool/rte_mempool.c b/lib/mempool/rte_mempool.c
index b7a19bea7185..12390a2c8155 100644
--- a/lib/mempool/rte_mempool.c
+++ b/lib/mempool/rte_mempool.c
@@ -50,9 +50,10 @@ static void
 mempool_event_callback_invoke(enum rte_mempool_event event,
 			      struct rte_mempool *mp);
 
-#define CACHE_FLUSHTHRESH_MULTIPLIER 1.5
-#define CALC_CACHE_FLUSHTHRESH(c)	\
-	((typeof(c))((c) * CACHE_FLUSHTHRESH_MULTIPLIER))
+/* Note: avoid using floating point since that compiler
+ * may not think that is constant.
+ */
+#define CALC_CACHE_FLUSHTHRESH(c) (((c) * 3) / 2)
 
 #if defined(RTE_ARCH_X86)
 /*
-- 
2.43.0