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segfault in libdSFMT caused by unaligned Array #9037

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rfourquet opened this issue Nov 17, 2014 · 0 comments
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segfault in libdSFMT caused by unaligned Array #9037

rfourquet opened this issue Nov 17, 2014 · 0 comments
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randomness Random number generation and the Random stdlib

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@rfourquet
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In 0f2d3ea, I incorrectly assumed that Julia Arrays are always 16-byte aligned (I misinterpreted this comment), which is not the case.
I can now see two ways to create a non-aligned Array, resize! (and functions calling jl_array_grow_end) and direct pointer manipulation:

a = Array(Float64, 0)
resize!(a, 1000)
Int(pointer(a)) % 16 # -> seems to be always 8 on my machine
rand!(a) # segfaults

and

a8 = Array(UInt8, 10000)
a = pointer_to_array(Ptr{Float64}(pointer(a8, 2)), 1000)
Int(pointer(a)) % 16 # -> 1
rand!(a) # segfaults
rfourquet added a commit that referenced this issue Nov 17, 2014
@rfourquet
fix #9037: segfault caused by incorrect alignment assumptions
4e0ae82 
The rand!(::MersenneTwister, A::Array{Float64}) assumed that the
array A was 16-byte aligned, which can be false (e.g. after a call
to resize!) and lead to a segfault in libdSFMT.
This was referenced Nov 17, 2014
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Merged
JeffBezanson added a commit that referenced this issue Nov 20, 2014
@JeffBezanson
Merge pull request #9040 from JuliaLang/rf/fix-align
85362bf 
fix #9037: segfault in libdSFMT caused by unaligned Array
bjarthur pushed a commit to bjarthur/julia that referenced this issue Nov 21, 2014
@rfourquet @bjarthur
fix JuliaLang#9037: segfault caused by incorrect alignment assumptions
a17979d 
The rand!(::MersenneTwister, A::Array{Float64}) assumed that the
array A was 16-byte aligned, which can be false (e.g. after a call
to resize!) and lead to a segfault in libdSFMT.
@ViralBShah ViralBShah added the randomness Random number generation and the Random stdlib label Nov 22, 2014
@nalimilan nalimilan mentioned this issue Nov 22, 2014
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waTeim pushed a commit to waTeim/julia that referenced this issue Nov 23, 2014
@rfourquet @waTeim
fix JuliaLang#9037: segfault caused by incorrect alignment assumptions
59767ad 
The rand!(::MersenneTwister, A::Array{Float64}) assumed that the
array A was 16-byte aligned, which can be false (e.g. after a call
to resize!) and lead to a segfault in libdSFMT.
@ViralBShah ViralBShah mentioned this issue Nov 25, 2015
Closed
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randomness Random number generation and the Random stdlib
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@ViralBShah @rfourquet