fix powermod correctness on unsigned power of half typemax#59680
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oscardssmith merged 2 commits intoJuliaLang:masterfrom Sep 30, 2025
Merged
fix powermod correctness on unsigned power of half typemax#59680oscardssmith merged 2 commits intoJuliaLang:masterfrom
powermod correctness on unsigned power of half typemax#59680oscardssmith merged 2 commits intoJuliaLang:masterfrom
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this one I think is basically "typo" territory and was clearly the original intention of the implementation |
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I'll leave this up for a few days and merge by EOW if no protest |
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Thanks! |
KristofferC
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Oct 4, 2025
the comment claims: > When the concrete type of p is signed and has the lowest value, > `p != 0 && p == -p` is equivalent to `p == typemin(typeof(p))` this is true, but fails to consider that `p == -p` is also true when `p = div(typemax(UInt), 2) + 1`, and that `p` is not necessarily signed leading to incorrect results on inputs like ``` julia> powermod(0x03, 0x80, 0x07) 0x01 ``` which should be `0x02` (cherry picked from commit bb3be0d)
KristofferC
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Oct 12, 2025
the comment claims: > When the concrete type of p is signed and has the lowest value, > `p != 0 && p == -p` is equivalent to `p == typemin(typeof(p))` this is true, but fails to consider that `p == -p` is also true when `p = div(typemax(UInt), 2) + 1`, and that `p` is not necessarily signed leading to incorrect results on inputs like ``` julia> powermod(0x03, 0x80, 0x07) 0x01 ``` which should be `0x02` (cherry picked from commit bb3be0d)
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DilumAluthge
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Jan 19, 2026
the comment claims: > When the concrete type of p is signed and has the lowest value, > `p != 0 && p == -p` is equivalent to `p == typemin(typeof(p))` this is true, but fails to consider that `p == -p` is also true when `p = div(typemax(UInt), 2) + 1`, and that `p` is not necessarily signed leading to incorrect results on inputs like ``` julia> powermod(0x03, 0x80, 0x07) 0x01 ``` which should be `0x02` (cherry picked from commit bb3be0d)
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DilumAluthge
pushed a commit
that referenced
this pull request
Jan 20, 2026
the comment claims: > When the concrete type of p is signed and has the lowest value, > `p != 0 && p == -p` is equivalent to `p == typemin(typeof(p))` this is true, but fails to consider that `p == -p` is also true when `p = div(typemax(UInt), 2) + 1`, and that `p` is not necessarily signed leading to incorrect results on inputs like ``` julia> powermod(0x03, 0x80, 0x07) 0x01 ``` which should be `0x02` (cherry picked from commit bb3be0d)
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the comment claims:
this is true, but fails to consider that
p == -pis also true whenp = div(typemax(UInt), 2) + 1, and thatpis not necessarily signedleading to incorrect results on inputs like
which should be
0x02