Bug fixes #752
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Bug fixes #752
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mjp41
commented
Feb 25, 2025
mjp41
commented
- Address overflow in alignment calculation not failing an allocation.
- Fix heuristic for how long to process a batch for
nwf
reviewed
Feb 25, 2025
src/snmalloc/mem/sizeclasstable.h
Outdated
| return ((alignment - 1) | (size - 1)) + 1; | ||
| size_t result = ((alignment - 1) | (size - 1)) + 1; | ||
| // Check for overflow and return the maximum size. | ||
| return result < size ? result - 1 : result; |
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I think (and I think z3 agrees, see below) that result < size implies result == 0, but it'd be good to write that down or perhaps use the other spelling?
(define-fun result ( (size (_ BitVec 32)) (align (_ BitVec 32)) ) (_ BitVec 32)
(bvadd #x00000001 (bvor (bvsub align #x00000001) (bvsub size #x00000001))))
(declare-const align (_ BitVec 32))
(declare-const size (_ BitVec 32))
(define-fun conjecture () Bool
(=> (bvult (result size align) size) (= (result size align) #x00000000)))
(assert (not conjecture))
(check-sat)
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Agreed. I used result-1 as it was a quick way to give -1 of the right size. I have moved to SIZE_MAX now, and also I rewrote it to generate better code with the sizeclass calc.
The bytes freed was not added to the total, but overrode it. This meant it never fired. This commit fixes that.
nwf
approved these changes
Feb 26, 2025
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