Reorder expression to avoid unsigned underflow #49
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Member
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ACK |
Contributor
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I am obligated to express dubiousness about tools that make people falsely believe there is a problem with that code, but the change is fine too. :P |
Collaborator
Author
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Going to close this; see bitcoin/bitcoin#23114 (comment) and subsequent discussion. |
Contributor
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There are two more instances of unnecessary wraps detected by ubsan, but they appear to be equally harmless to me: diff --git a/src/minisketch/src/sketch_impl.h b/src/minisketch/src/sketch_impl.h
index 4547b742f2..88d889ae79 100644
--- a/src/minisketch/src/sketch_impl.h
+++ b/src/minisketch/src/sketch_impl.h
@@ -26,7 +26,7 @@ void PolyMod(const std::vector<typename F::Elem>& mod, std::vector<typename F::E
if (term != 0) {
typename F::Multiplier mul(field, term);
for (size_t x = 0; x < mod.size() - 1; ++x) {
- val[val.size() - modsize + 1 + x] ^= mul(mod[x]);
+ val[val.size() + 1 + x - modsize] ^= mul(mod[x]);
}
}
}
@@ -51,7 +51,7 @@ void DivMod(const std::vector<typename F::Elem>& mod, std::vector<typename F::El
if (term != 0) {
typename F::Multiplier mul(field, term);
for (size_t x = 0; x < mod.size() - 1; ++x) {
- val[val.size() - modsize + 1 + x] ^= mul(mod[x]);
+ val[val.size() +1 + x - modsize] ^= mul(mod[x]);
}
}
} |
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See bitcoin/bitcoin#23114 (comment)