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toolchain: Add single arguments evaluation macros for min and max

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MAX() and MIN() were evaluating arguments twice. If arguments are
functions they were called twice which resulted in bigger code
and potential misbehavior.

Added alternative macros (Z_MAX, Z_MIN) which can be used instead.
Macros have usage limitations thus they are not replacements. They
are also relying on GCC extension thus placed in gcc.h

Signed-off-by: Krzysztof Chruscinski <krzysztof.chruscinski@nordicsemi.no>
This commit is contained in:
Krzysztof Chruscinski 2019-07-29 15:33:05 +02:00 • committed by Carles Cufí
commit bea966dea1
2 changed files with 38 additions and 0 deletions
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10
include/sys/util.h
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@ -89,10 +89,20 @@ constexpr size_t ARRAY_SIZE(T(&)[N]) { return N; }
#define INLINE #define INLINE
#endif #endif
/** @brief Return larger value of two provided expressions.
*
* @note Arguments are evaluated twice. See Z_MAX for GCC only, single
* evaluation version.
*/
#ifndef MAX #ifndef MAX
#define MAX(a, b) (((a) > (b)) ? (a) : (b)) #define MAX(a, b) (((a) > (b)) ? (a) : (b))
#endif #endif
/** @brief Return smaller value of two provided expressions.
*
* @note Arguments are evaluated twice. See Z_MIN for GCC only, single
* evaluation version.
*/
#ifndef MIN #ifndef MIN
#define MIN(a, b) (((a) < (b)) ? (a) : (b)) #define MIN(a, b) (((a) < (b)) ? (a) : (b))
#endif #endif

28
include/toolchain/gcc.h
View file

@ -415,4 +415,32 @@ do { \
__asm__ __volatile__ ("" ::: "memory"); \ __asm__ __volatile__ ("" ::: "memory"); \
} while (false) } while (false)
/** @brief Return larger value of two provided expressions.
*
* Macro ensures that expressions are evaluated only once.
*
* @note Macro has limited usage compared to the standard macro as it cannot be
* used:
* - to generate constant integer, e.g. __aligned(Z_MAX(4,5))
* - static variable, e.g. array like static u8_t array[Z_MAX(...)];
*/
#define Z_MAX(a, b) ({ \
/* random suffix to avoid naming conflict */ \
__typeof__(a) _value_a_ = (a); \
__typeof__(b) _value_b_ = (b); \
_value_a_ > _value_b_ ? _value_a_ : _value_b_; \
})
/** @brief Return smaller value of two provided expressions.
*
* Macro ensures that expressions are evaluated only once. See @ref Z_MAX for
* macro limitations.
*/
#define Z_MIN(a, b) ({ \
/* random suffix to avoid naming conflict */ \
__typeof__(a) _value_a_ = (a); \
__typeof__(b) _value_b_ = (b); \
_value_a_ < _value_b_ ? _value_a_ : _value_b_; \
})
#endif /* ZEPHYR_INCLUDE_TOOLCHAIN_GCC_H_ */ #endif /* ZEPHYR_INCLUDE_TOOLCHAIN_GCC_H_ */