Re: [RFC PATCH 05/19] graph: fix variable shadowing errors

Stephen Hemminger
2025-11-06T15:50:19Z

On Thu, 6 Nov 2025 14:09:34 +0000
Bruce Richardson <bruce.richardson@intel.com> wrote:

> The nested use of MIN/MAX macros causes shadowing due to the use of the
> hard-coded temporary variable names in the macros. We can fix this in
> graph library by using MIN_T/MAX_T macros instead, which actually makes
> more sense in some circumstances:
>
> * when defining SZ, use of RTE_MIN_T makes sense as the comments says it
> is defined to be usable for compile-time evaluation.
> * for the size calculations, RTE_MAX_T is also useful as it explicitly
> encodes the type, making it clear that we are evaluating the size
> variables as "int" type, larger than the uin16_t size is defined as.
>
> Fixes: b6ef3794b866 ("graph: move node clone name func into private as common")
> Cc: stable@dpdk.org
>
> Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>

I had a patch series (not sent) for lots of these.
This is how I addressed min/max

From 5c8d69c734f90a774f83aaf47bc6c61bb19f411e Mon Sep 17 00:00:00 2001
From: Stephen Hemminger <stephen@networkplumber.org>
Date: Thu, 28 Aug 2025 09:24:54 -0700
Subject: [PATCH 06/13] eal: add more min/max helpers

Add RTE_MIN3() to handle case of RTE_MIN(RTE_MIN(...)).
Change name of local temporary variables in RTE_MAX()
to allow for combinations of RTE_MIN(RTE_MAX(...)) without
causing shadow declaration warnings.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
lib/eal/include/rte_common.h | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/lib/eal/include/rte_common.h b/lib/eal/include/rte_common.h
index 9e7d84f929..1f0edef73f 100644
--- a/lib/eal/include/rte_common.h
+++ b/lib/eal/include/rte_common.h
@@ -799,6 +799,19 @@ __extension__ typedef uint64_t RTE_MARKER64[0];
_a < _b ? _a : _b; \
})

+/**
+ * Macro to return the minimum of three numbers
+ */
+#define RTE_MIN3(a, b, c) \
+ __extension__ ({ \
+ typeof (a) _a = (a); \
+ typeof (b) _b = (b); \
+ typeof (c) _c = (c); \
+ _a < _b ? (_a < _c ? _a : _c) \
+ : (_b < _c ? _b : _c); \
+ })
+
+
/**
* Macro to return the minimum of two numbers
*
@@ -814,9 +827,9 @@ __extension__ typedef uint64_t RTE_MARKER64[0];
*/
#define RTE_MAX(a, b) \
__extension__ ({ \
- typeof (a) _a = (a); \
- typeof (b) _b = (b); \
- _a > _b ? _a : _b; \
+ typeof (a) _ax = (a); \
+ typeof (b) _bx = (b); \
+ _ax > _bx ? _ax : _bx; \
})

/**
--
2.51.0