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Avoid double-counting in Base.summarysize #54555

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Avoid double-counting in Base.summarysize #54555

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10 changes: 7 additions & 3 deletions base/summarysize.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -56,9 +56,13 @@ function summarysize(obj;
end
else
nf = nfields(x)
ft = typeof(x).types
if !isbitstype(ft[i]) && isdefined(x, i)
val = getfield(x, i)
dt = typeof(x)
dtfd = Base.DataTypeFieldDesc(dt)
if isdefined(x, i)
f = getfield(x, i)
if dtfd[i].isptr || !Base.datatype_pointerfree(typeof(f))
val = f
end
end
end
if nf > i
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11 changes: 11 additions & 0 deletions test/misc.jl
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Expand Up @@ -573,6 +573,17 @@ end
# issue #44780
@test summarysize(BigInt(2)^1000) > summarysize(BigInt(2))

# issue #53061
mutable struct S53061
x::Union{Float64, Tuple{Float64, Float64}}
y::Union{Float64, Tuple{Float64, Float64}}
end
let s = S53061[S53061(rand(), (rand(),rand())) for _ in 1:10^5]
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not a big deal, but does the array have to be this big to reproduce this?

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checked, the answer is yes, at least in the current form of the struct, more you reduce the size more you need attempts to find them unequal

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@Tortar Tortar May 22, 2024 •
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e.g. this needs 10 attempts more or less with 10^4: allequal(Base.summarysize(s) for i in 1:10) # usually false.

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why is this nondeterministic? That makes very little sense to me.

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to me too actually, but I'm not qualified enough to answer :D

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It's because the old code has to allocate a box for the value, which it should not have to do, and so the later uniquing by address becomes dependent on GC/allocator behavior. The correct way to fix this is to iterate over the pointers inside a struct instead of over its fields (some fields might be inlined but contain embedded pointers).

sz1 = summarysize(s)
sz2 = summarysize(s)
@test sz1 == sz2
end

## test conversion from UTF-8 to UTF-16 (for Windows APIs)

# empty arrays
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