|WARNING| pw156944 [dpdk-dev v1] cryptodev: introduce constant-time memory comparison

[checkpatch at dpdk.org]

Test-Label: checkpatch
Test-Status: WARNING
http://dpdk.org/patch/156944

_coding style issues_


ERROR:COMPLEX_MACRO: Macros with complex values should be enclosed in parentheses
#209: FILE: lib/cryptodev/rte_cryptodev.h:95:
+#define rte_consttime_memcmp(a, b, n) __extension__ ({ \
+	const volatile uint8_t *__pa = (const volatile uint8_t *)(a); \
+	const volatile uint8_t *__pb = (const volatile uint8_t *)(b); \
+	uint8_t __result = 0; \
+	for (size_t __i = 0; __i < (n); __i++) \
+		__result |= __pa[__i] ^ __pb[__i]; \
+	__result; \
+})

BUT SEE:

   do {} while (0) advice is over-stated in a few situations:

   The more obvious case is macros, like MODULE_PARM_DESC, invoked at
   file-scope, where C disallows code (it must be in functions).  See
   $exceptions if you have one to add by name.

   More troublesome is declarative macros used at top of new scope,
   like DECLARE_PER_CPU.  These might just compile with a do-while-0
   wrapper, but would be incorrect.  Most of these are handled by
   detecting struct,union,etc declaration primitives in $exceptions.

   Theres also macros called inside an if (block), which "return" an
   expression.  These cannot do-while, and need a ({}) wrapper.

   Enjoy this qualification while we work to improve our heuristics.

WARNING:MISSING_FIXES_TAG: The commit message has 'stable@', perhaps it also needs a 'Fixes:' tag?

total: 1 errors, 1 warnings, 93 lines checked