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macro: relax CONST_MAX() type check a tiny bit

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This checked for strict type compatibility so far, which mean CONST_MAX()
couldn't be used on two differently signed integers, even though
conceptually there's nothing wrong with allowing that here, as C
correctly picks the larger type in the ternary op.

hence, let's explicitly whitelist integer comparisons here, as long as
the signedness matches.
This commit is contained in:
Lennart Poettering
2021-07-30 15:56:56 +02:00
parent a4d9c121cc
commit addae96a1a
1 changed files with 19 additions and 2 deletions
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src/fundamental/macro-fundamental.h
+19 -2
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@@ -70,12 +70,29 @@
UNIQ_T(A, aq) > UNIQ_T(B, bq) ? UNIQ_T(A, aq) : UNIQ_T(B, bq); \
})
/* evaluates to (void) if _A or _B are not constant or of different types */
#define IS_UNSIGNED_INTEGER_TYPE(type) \
(__builtin_types_compatible_p(typeof(type), unsigned char) || \
__builtin_types_compatible_p(typeof(type), unsigned short) || \
__builtin_types_compatible_p(typeof(type), unsigned) || \
__builtin_types_compatible_p(typeof(type), unsigned long) || \
__builtin_types_compatible_p(typeof(type), unsigned long long))
#define IS_SIGNED_INTEGER_TYPE(type) \
(__builtin_types_compatible_p(typeof(type), signed char) || \
__builtin_types_compatible_p(typeof(type), signed short) || \
__builtin_types_compatible_p(typeof(type), signed) || \
__builtin_types_compatible_p(typeof(type), signed long) || \
__builtin_types_compatible_p(typeof(type), signed long long))
/* Evaluates to (void) if _A or _B are not constant or of different types (being integers of different sizes
* is also OK as long as the signedness matches) */
#define CONST_MAX(_A, _B) \
(__builtin_choose_expr( \
__builtin_constant_p(_A) && \
__builtin_constant_p(_B) && \
__builtin_types_compatible_p(typeof(_A), typeof(_B)), \
(__builtin_types_compatible_p(typeof(_A), typeof(_B)) || \
(IS_UNSIGNED_INTEGER_TYPE(_A) && IS_UNSIGNED_INTEGER_TYPE(_B)) || \
(IS_SIGNED_INTEGER_TYPE(_A) && IS_SIGNED_INTEGER_TYPE(_B))), \
((_A) > (_B)) ? (_A) : (_B), \
VOID_0))