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Bugfix: Use Base.aligned_sizeof instead of sizeof in Mmap.mmap #58998

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Bugfix: Use Base.aligned_sizeof instead of sizeof in Mmap.mmap #58998

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5d81681
Use aligned_sizeof instead of sizeof
JonasIsensee Jul 14, 2025
3f88efa
non isbits now (correctly) throws an ArgumentError
JonasIsensee Jul 14, 2025
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8 changes: 4 additions & 4 deletions stdlib/Mmap/src/Mmap.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -187,16 +187,16 @@ like HDF5 (which can be used with memory-mapping).
"""
function mmap(io::IO,
::Type{Array{T,N}}=Vector{UInt8},
dims::NTuple{N,Integer}=(div(filesize(io)-position(io),sizeof(T)),),
dims::NTuple{N,Integer}=(div(filesize(io)-position(io),Base.aligned_sizeof(T)),),
offset::Integer=position(io); grow::Bool=true, shared::Bool=true) where {T,N}
# check inputs
isopen(io) || throw(ArgumentError("$io must be open to mmap"))
isbitstype(T) || throw(ArgumentError("unable to mmap $T; must satisfy isbitstype(T) == true"))

len = sizeof(T)
len = Base.aligned_sizeof(T)
for l in dims
len, overflow = Base.Checked.mul_with_overflow(promote(len, l)...)
overflow && throw(ArgumentError("requested size prod($((sizeof(T), dims...))) too large, would overflow typeof(size(T)) == $(typeof(len))"))
overflow && throw(ArgumentError("requested size prod($((len, dims...))) too large, would overflow typeof(size(T)) == $(typeof(len))"))
end
len >= 0 || throw(ArgumentError("requested size must be ≥ 0, got $len"))
len == 0 && return Array{T}(undef, ntuple(x->0,Val(N)))
Expand Down Expand Up @@ -267,7 +267,7 @@ end

mmap(file::AbstractString,
::Type{T}=Vector{UInt8},
dims::NTuple{N,Integer}=(div(filesize(file),sizeof(eltype(T))),),
dims::NTuple{N,Integer}=(div(filesize(file),Base.aligned_sizeof(eltype(T))),),
offset::Integer=Int64(0); grow::Bool=true, shared::Bool=true) where {T<:Array,N} =
open(io->mmap(io, T, dims, offset; grow=grow, shared=shared), file, isfile(file) ? "r" : "w+")::Array{eltype(T),N}

Expand Down
14 changes: 13 additions & 1 deletion stdlib/Mmap/test/runtests.jl
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Expand Up @@ -44,7 +44,7 @@ s = open(file)
@test length(@inferred mmap(s, Vector{Int8}, 12, 0; grow=false)) == 12
@test length(@inferred mmap(s, Vector{Int8}, 12, 0; shared=false)) == 12
close(s)
@test_throws ErrorException mmap(file, Vector{Ref}) # must be bit-type
@test_throws ArgumentError mmap(file, Vector{Ref}) # must be bit-type
GC.gc(); GC.gc()

file = tempname() # new name to reduce chance of issues due slow windows fs
Expand Down Expand Up @@ -343,6 +343,18 @@ end
GC.gc()
rm(file)

# test for #58982
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Should this be put into a @testset to make failures here more localized?

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We can wrap it into a testset.
I just tried to match the (oldish) style of the test file as closely as possible.

file = tempname()
primitive type PrimType9Bytes 9*8 end
arr = Vector{PrimType9Bytes}(undef, 2)
write(file, arr)
m = mmap(file, Vector{PrimType9Bytes})
@test length(m) == 2
@test m[1] == arr[1]
@test m[2] == arr[2]
finalize(m); m = nothing; GC.gc()
rm(file)

@testset "Docstrings" begin
@test isempty(Docs.undocumented_names(Mmap))
end