* [PATCH] eal: silence -Wconstant-logical-operand in RTE_IS_POWER_OF_2
@ 2026-05-18 16:33 Stephen Hemminger
2026-05-18 16:56 ` Bruce Richardson
` (2 more replies)
0 siblings, 3 replies; 5+ messages in thread
From: Stephen Hemminger @ 2026-05-18 16:33 UTC (permalink / raw)
To: dev
Cc: Stephen Hemminger, stable, Jack Bond-Preston, Gavin Hu,
Honnappa Nagarahalli, Pablo de Lara
Newer GCC warns when a non-boolean constant is an operand of &&, which
trips whenever RTE_IS_POWER_OF_2 is used in a static_assert with a
power-of-two literal. Make the zero check explicit.
Fixes: 7c872b96983a ("hash: validate hash bucket entries while compiling")
Cc: stable@dpdk.org
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
lib/eal/include/rte_bitops.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/eal/include/rte_bitops.h b/lib/eal/include/rte_bitops.h
index aa6ac73abb..d2719ecd5e 100644
--- a/lib/eal/include/rte_bitops.h
+++ b/lib/eal/include/rte_bitops.h
@@ -1299,7 +1299,7 @@ rte_fls_u64(uint64_t x)
/**
* Macro to return 1 if n is a power of 2, 0 otherwise
*/
-#define RTE_IS_POWER_OF_2(n) ((n) && !(((n) - 1) & (n)))
+#define RTE_IS_POWER_OF_2(n) ((n) != 0 && !(((n) - 1) & (n)))
/**
* Returns true if n is a power of 2
--
2.53.0
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH] eal: silence -Wconstant-logical-operand in RTE_IS_POWER_OF_2
2026-05-18 16:33 [PATCH] eal: silence -Wconstant-logical-operand in RTE_IS_POWER_OF_2 Stephen Hemminger
@ 2026-05-18 16:56 ` Bruce Richardson
2026-05-18 17:10 ` Stephen Hemminger
2026-05-19 9:26 ` Jack Bond-Preston
2026-05-19 13:49 ` [PATCH v2] " Stephen Hemminger
2 siblings, 1 reply; 5+ messages in thread
From: Bruce Richardson @ 2026-05-18 16:56 UTC (permalink / raw)
To: Stephen Hemminger
Cc: dev, stable, Jack Bond-Preston, Gavin Hu, Honnappa Nagarahalli,
Pablo de Lara
On Mon, May 18, 2026 at 09:33:31AM -0700, Stephen Hemminger wrote:
> Newer GCC warns when a non-boolean constant is an operand of &&, which
> trips whenever RTE_IS_POWER_OF_2 is used in a static_assert with a
> power-of-two literal. Make the zero check explicit.
>
> Fixes: 7c872b96983a ("hash: validate hash bucket entries while compiling")
> Cc: stable@dpdk.org
>
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
One further suggestion below, since you are changing this.
> ---
> lib/eal/include/rte_bitops.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/eal/include/rte_bitops.h b/lib/eal/include/rte_bitops.h
> index aa6ac73abb..d2719ecd5e 100644
> --- a/lib/eal/include/rte_bitops.h
> +++ b/lib/eal/include/rte_bitops.h
> @@ -1299,7 +1299,7 @@ rte_fls_u64(uint64_t x)
> /**
> * Macro to return 1 if n is a power of 2, 0 otherwise
> */
> -#define RTE_IS_POWER_OF_2(n) ((n) && !(((n) - 1) & (n)))
> +#define RTE_IS_POWER_OF_2(n) ((n) != 0 && !(((n) - 1) & (n)))
>
I'd also suggest changing the second part of the && to match, changing the
"!" for explicit "== 0":
#define RTE_IS_POWER_OF_2(n) ((n) != 0 && (((n) - 1) & (n)) == 0)
> /**
> * Returns true if n is a power of 2
> --
> 2.53.0
>
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH] eal: silence -Wconstant-logical-operand in RTE_IS_POWER_OF_2
2026-05-18 16:56 ` Bruce Richardson
@ 2026-05-18 17:10 ` Stephen Hemminger
0 siblings, 0 replies; 5+ messages in thread
From: Stephen Hemminger @ 2026-05-18 17:10 UTC (permalink / raw)
To: Bruce Richardson
Cc: dev, stable, Jack Bond-Preston, Gavin Hu, Honnappa Nagarahalli,
Pablo de Lara
On Mon, 18 May 2026 17:56:08 +0100
Bruce Richardson <bruce.richardson@intel.com> wrote:
> I'd also suggest changing the second part of the && to match, changing the
> "!" for explicit "== 0":
>
> #define RTE_IS_POWER_OF_2(n) ((n) != 0 && (((n) - 1) & (n)) == 0)
Was heading for the smallest possible part
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] eal: silence -Wconstant-logical-operand in RTE_IS_POWER_OF_2
2026-05-18 16:33 [PATCH] eal: silence -Wconstant-logical-operand in RTE_IS_POWER_OF_2 Stephen Hemminger
2026-05-18 16:56 ` Bruce Richardson
@ 2026-05-19 9:26 ` Jack Bond-Preston
2026-05-19 13:49 ` [PATCH v2] " Stephen Hemminger
2 siblings, 0 replies; 5+ messages in thread
From: Jack Bond-Preston @ 2026-05-19 9:26 UTC (permalink / raw)
To: Stephen Hemminger, dev
Cc: stable, Gavin Hu, Honnappa Nagarahalli, Pablo de Lara
On 18/05/2026 17:33, Stephen Hemminger wrote:
> Newer GCC warns when a non-boolean constant is an operand of &&, which
> trips whenever RTE_IS_POWER_OF_2 is used in a static_assert with a
> power-of-two literal. Make the zero check explicit.
>
> Fixes: 7c872b96983a ("hash: validate hash bucket entries while compiling")
> Cc: stable@dpdk.org
>
> Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
> ---
> lib/eal/include/rte_bitops.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/eal/include/rte_bitops.h b/lib/eal/include/rte_bitops.h
> index aa6ac73abb..d2719ecd5e 100644
> --- a/lib/eal/include/rte_bitops.h
> +++ b/lib/eal/include/rte_bitops.h
> @@ -1299,7 +1299,7 @@ rte_fls_u64(uint64_t x)
> /**
> * Macro to return 1 if n is a power of 2, 0 otherwise
> */
> -#define RTE_IS_POWER_OF_2(n) ((n) && !(((n) - 1) & (n)))
> +#define RTE_IS_POWER_OF_2(n) ((n) != 0 && !(((n) - 1) & (n)))
>
> /**
> * Returns true if n is a power of 2
Acked-by: Jack Bond-Preston <jack.bond-preston@foss.arm.com>
^ permalink raw reply [flat|nested] 5+ messages in thread* [PATCH v2] eal: silence -Wconstant-logical-operand in RTE_IS_POWER_OF_2
2026-05-18 16:33 [PATCH] eal: silence -Wconstant-logical-operand in RTE_IS_POWER_OF_2 Stephen Hemminger
2026-05-18 16:56 ` Bruce Richardson
2026-05-19 9:26 ` Jack Bond-Preston
@ 2026-05-19 13:49 ` Stephen Hemminger
2 siblings, 0 replies; 5+ messages in thread
From: Stephen Hemminger @ 2026-05-19 13:49 UTC (permalink / raw)
To: dev
Cc: Stephen Hemminger, stable, Bruce Richardson, Jack Bond-Preston,
Pablo de Lara, Gavin Hu, Honnappa Nagarahalli
Newer GCC warns when a non-boolean constant is an operand of &&, which
trips whenever RTE_IS_POWER_OF_2 is used in a static_assert with a
power-of-two literal. Make the zero check explicit.
Fixes: 7c872b96983a ("hash: validate hash bucket entries while compiling")
Cc: stable@dpdk.org
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Jack Bond-Preston <jack.bond-preston@foss.arm.com>
---
v2 - use suggestion to make both sides comparisons
Note: AI incorrectly complains about multiple evaluations in this macro
but that has always been the case, and has to be macro
for use with static assert.
lib/eal/include/rte_bitops.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/eal/include/rte_bitops.h b/lib/eal/include/rte_bitops.h
index aa6ac73abb..b170447714 100644
--- a/lib/eal/include/rte_bitops.h
+++ b/lib/eal/include/rte_bitops.h
@@ -1299,7 +1299,7 @@ rte_fls_u64(uint64_t x)
/**
* Macro to return 1 if n is a power of 2, 0 otherwise
*/
-#define RTE_IS_POWER_OF_2(n) ((n) && !(((n) - 1) & (n)))
+#define RTE_IS_POWER_OF_2(n) ((n) != 0 && (((n) - 1) & (n)) == 0)
/**
* Returns true if n is a power of 2
--
2.53.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
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2026-05-18 16:33 [PATCH] eal: silence -Wconstant-logical-operand in RTE_IS_POWER_OF_2 Stephen Hemminger
2026-05-18 16:56 ` Bruce Richardson
2026-05-18 17:10 ` Stephen Hemminger
2026-05-19 9:26 ` Jack Bond-Preston
2026-05-19 13:49 ` [PATCH v2] " Stephen Hemminger
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