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fundamental: Add overflow-safe math helpers

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ADD_SAFE/SUB_SAFE/MUL_SAFE do addition/subtraction/multiplication
respectively with an overflow check. If an overflow occurs these return
false, otherwise true. Example: (c = a + b) would become ADD_SAFE(&c, a,
b)

INC_SAFE/DEC_SAFE/MUL_ASSIGN_SAFE are like above but they also reassign
the first argument. Example: (a += b) would become INC_SAFE(&a, b)
This commit is contained in:
Adrian Vovk
2024-02-13 13:08:20 -05:00
parent 6d55e3a364
commit a7a67dfd9d
6 changed files with 179 additions and 8 deletions
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src/fundamental/macro-fundamental.h
+25 -1
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@@ -249,6 +249,30 @@
CONST_ISPOWEROF2(_x); \
}))
#define ADD_SAFE(ret, a, b) (!__builtin_add_overflow(a, b, ret))
#define INC_SAFE(a, b) __INC_SAFE(UNIQ, a, b)
#define __INC_SAFE(q, a, b) \
({ \
const typeof(a) UNIQ_T(A, q) = (a); \
ADD_SAFE(UNIQ_T(A, q), *UNIQ_T(A, q), b); \
})
#define SUB_SAFE(ret, a, b) (!__builtin_sub_overflow(a, b, ret))
#define DEC_SAFE(a, b) __DEC_SAFE(UNIQ, a, b)
#define __DEC_SAFE(q, a, b) \
({ \
const typeof(a) UNIQ_T(A, q) = (a); \
SUB_SAFE(UNIQ_T(A, q), *UNIQ_T(A, q), b); \
})
#define MUL_SAFE(ret, a, b) (!__builtin_mul_overflow(a, b, ret))
#define MUL_ASSIGN_SAFE(a, b) __MUL_ASSIGN_SAFE(UNIQ, a, b)
#define __MUL_ASSIGN_SAFE(q, a, b) \
({ \
const typeof(a) UNIQ_T(A, q) = (a); \
MUL_SAFE(UNIQ_T(A, q), *UNIQ_T(A, q), b); \
})
#define LESS_BY(a, b) __LESS_BY(UNIQ, (a), UNIQ, (b))
#define __LESS_BY(aq, a, bq, b) \
({ \
@@ -298,7 +322,7 @@
const typeof(y) UNIQ_T(A, q) = (y); \
const typeof(x) UNIQ_T(B, q) = DIV_ROUND_UP((x), UNIQ_T(A, q)); \
typeof(x) UNIQ_T(C, q); \
__builtin_mul_overflow(UNIQ_T(B, q), UNIQ_T(A, q), &UNIQ_T(C, q)) ? (typeof(x)) -1 : UNIQ_T(C, q); \
MUL_SAFE(&UNIQ_T(C, q), UNIQ_T(B, q), UNIQ_T(A, q)) ? UNIQ_T(C, q) : (typeof(x)) -1; \
})
#define ROUND_UP(x, y) __ROUND_UP(UNIQ, (x), (y))