From 5d81681461b349c4d89e757af577309cedb07502 Mon Sep 17 00:00:00 2001
From: Jonas Isensee <jonas.isensee@web.de>
Date: Mon, 14 Jul 2025 16:44:11 +0200
Subject: [PATCH 1/3] Use aligned_sizeof instead of sizeof

---
 stdlib/Mmap/src/Mmap.jl      |  8 ++++----
 stdlib/Mmap/test/runtests.jl | 12 ++++++++++++
 2 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/stdlib/Mmap/src/Mmap.jl b/stdlib/Mmap/src/Mmap.jl
index 7d57bf053940d..c527123d51bb8 100644
--- a/stdlib/Mmap/src/Mmap.jl
+++ b/stdlib/Mmap/src/Mmap.jl
@@ -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)))
@@ -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}
 
diff --git a/stdlib/Mmap/test/runtests.jl b/stdlib/Mmap/test/runtests.jl
index f4b6abb147fb7..61ed432f90c4f 100644
--- a/stdlib/Mmap/test/runtests.jl
+++ b/stdlib/Mmap/test/runtests.jl
@@ -343,6 +343,18 @@ end
 GC.gc()
 rm(file)
 
+# test for #58982
+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

From 3f88efa56779185c39ddb7b0c3003e80744cc54e Mon Sep 17 00:00:00 2001
From: Jonas Isensee <jonas.isensee@web.de>
Date: Mon, 14 Jul 2025 22:53:19 +0200
Subject: [PATCH 2/3] non isbits now (correctly) throws an ArgumentError

---
 stdlib/Mmap/test/runtests.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/stdlib/Mmap/test/runtests.jl b/stdlib/Mmap/test/runtests.jl
index 61ed432f90c4f..7875dc45a1e19 100644
--- a/stdlib/Mmap/test/runtests.jl
+++ b/stdlib/Mmap/test/runtests.jl
@@ -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

From 9b4ba24a0b002021240c620d6b88c67f2b5d2a3a Mon Sep 17 00:00:00 2001
From: Jonas Isensee <jonas.isensee@web.de>
Date: Thu, 17 Jul 2025 15:56:26 +0200
Subject: [PATCH 3/3] wrap new test into testset

---
 stdlib/Mmap/test/runtests.jl | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/stdlib/Mmap/test/runtests.jl b/stdlib/Mmap/test/runtests.jl
index 7875dc45a1e19..064217a24e3be 100644
--- a/stdlib/Mmap/test/runtests.jl
+++ b/stdlib/Mmap/test/runtests.jl
@@ -343,17 +343,18 @@ end
 GC.gc()
 rm(file)
 
-# test for #58982
-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 "test for #58982 - mmap with primitive types" begin
+    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)
+end
 
 @testset "Docstrings" begin
     @test isempty(Docs.undocumented_names(Mmap))