Skip to content

Fix incorrect result for Base.invmod(<:Signed, <:Unsigned) #58010

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 5 commits into from
May 8, 2025
Merged

Fix incorrect result for Base.invmod(<:Signed, <:Unsigned) #58010

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
5 commits
Select commit Hold shift + click to select a range
a5530ea
Fixed incorrect results for invmod(<:Signed, <:Unsigned)
alexp616 Apr 4, 2025
7733331
Added test cases for invmod(<:Signed, <:Unsigned)
alexp616 Apr 4, 2025
5982b93
Apply suggestions from code review
fingolfin May 8, 2025
dd652f4
Update test/intfuncs.jl
fingolfin May 8, 2025
d17424e
Update test/intfuncs.jl
fingolfin May 8, 2025
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 1 addition & 1 deletion base/intfuncs.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -286,7 +286,7 @@ function invmod(n::Integer, m::Integer)
g, x, y = gcdx(n, m)
g != 1 && throw(DomainError((n, m), LazyString("Greatest common divisor is ", g, ".")))
# Note that m might be negative here.
if n isa Unsigned && hastypemax(typeof(n)) && x > typemax(n)>>1
if x isa Unsigned && hastypemax(typeof(x)) && x > typemax(x)>>1
# x might have wrapped if it would have been negative
# adding back m forces a correction
x += m
Expand Down
7 changes: 7 additions & 0 deletions test/intfuncs.jl
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -258,6 +258,13 @@ end
@test invmod(T(3), T(124))::T == 83
end

for T in (Int8, Int16, Int32, Int64, Int128)
@test invmod(T(3), unsigned(T)(124)) == 83
end

# Verify issue described in PR 58010 is fixed
@test invmod(UInt8(3), UInt16(50000)) === 0x411b

for T in (Int8, UInt8)
for x in typemin(T):typemax(T)
for m in typemin(T):typemax(T)
Expand Down