Although unsigned integer overflow is not undefined behavior, it’s preferable to eliminate the need for an UBSan suppression for it.
~This is an alternative to #29541.~
script/interpreter.cpp
#29543
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Type | Reviewers |
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ACK | sipa |
Concept ACK | hernanmarino |
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Although unsigned integer overflow is not undefined behavior, it's
preferable to eliminate the need for a UBSan suppression for it.
Needs rebase.
Rebased.
But see also the discussion in #29541. I would prefer narrowing the suppression to as little as possible…
Anything in your mind without growing the diff up to 10+ lines?
but without touching the ancient code.
I still believe that the suggested diff is reviewable.
ACK 754ba687ccc16bb609c9b22bc2d3bbf0a82d5bce
This is consensus-critical code, so I’ve carefully verified that this change does not modify behavior:
stacktop()
and altstacktop()
use either a small negative integer literal (between -6
and -1
) as argument, or small int
values between -42 and -1 (in the OP_CHECKMULTISIG code).int
and 32-bit or 64-bit size_t
.stack.size()
) is always an unsigned type of rank at least as high as int
’s, which is sized.int
and size_t
will involve an conversion to size_t
of both inputs; for negative int
s i
, that conversion is 2^N + i
, with N the size of size_t
(32 or 64).stack.size() + (i)
is therefor equal to 2^N + stack.size() + i
, which due to the modular nature of the unsigned type size_t
, equals (stack.size() + i) mod 2^N
.(i)
is a small strictly negative int, and thus (-i)
is a small strictly positive int.size_t
happens, and thus stack.size() - (-i)
is (stack.size() + i) mod 2^N
.🐙 This pull request conflicts with the target branch and needs rebase.
⌛ There hasn’t been much activity lately and the patch still needs rebase. What is the status here?