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Prevent stack overflow in Profile #31893

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May 2, 2019
Merged

Prevent stack overflow in Profile #31893

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d2e7808
Prevent stack overflow in Profile
Keno May 1, 2019
6639009
fixup! Prevent stack overflow in Profile
vtjnash May 1, 2019
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45 changes: 26 additions & 19 deletions stdlib/Profile/src/Profile.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -560,26 +560,33 @@ function tree!(root::StackFrameTree{T}, all::Vector{UInt64}, lidict::Union{LineI
return root
end

# Print a "branch" starting at a particular level. This gets called recursively.
# Print the stack frame tree starting at a particular root. Uses a worklist to
# avoid stack overflows.
function tree(io::IO, bt::StackFrameTree, level::Int, cols::Int, fmt::ProfileFormat, noisefloor::Int)
level > fmt.maxdepth && return
isempty(bt.down) && return
# Order the line information
nexts = collect(values(bt.down))
lilist = collect(frame.frame for frame in nexts)
counts = collect(frame.count for frame in nexts)
# Generate the string for each line
strs = tree_format(lilist, counts, level, cols)
# Recurse to the next level
for i in liperm(lilist)
down = nexts[i]
count = down.count
count < fmt.mincount && continue
count < noisefloor && continue
str = strs[i]
println(io, isempty(str) ? "$count unknown stackframe" : str)
noisefloor_down = fmt.noisefloor > 0 ? floor(Int, fmt.noisefloor * sqrt(count)) : 0
tree(io, down, level + 1, cols, fmt, noisefloor_down)
worklist = Tuple{StackFrameTree, Int, Int, Union{String, Nothing}}[
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Suggested change
worklist = Tuple{StackFrameTree, Int, Int, Union{String, Nothing}}[
worklist = [(bt, level, noisefloor, "")]

No sense in reducing performance and introducing pointless complexity.

But I don't think this translation is correct: it doesn't seem expected that str would suddenly get appended to the worklist, when it wasn't there before the translation. It looks like this would print all level 0 items, followed by all level 1 items, followed by all level 2 items, and so on. (indeed, running this PR on @profile peakflops(), that's exactly the behavior that I see happen)

(bt, level, noisefloor, nothing)]
while !isempty(worklist)
(bt, level, noisefloor, str) = popfirst!(worklist)
str !== nothing && println(io, str)
level > fmt.maxdepth && continue
isempty(bt.down) && continue
# Order the line information
nexts = collect(values(bt.down))
lilist = collect(frame.frame for frame in nexts)
counts = collect(frame.count for frame in nexts)
# Generate the string for each line
strs = tree_format(lilist, counts, level, cols)
# Recurse to the next level
for i in liperm(lilist)
down = nexts[i]
count = down.count
count < fmt.mincount && continue
count < noisefloor && continue
str = strs[i]
isempty(str) && (str = "$count unknown stackframe")
noisefloor_down = fmt.noisefloor > 0 ? floor(Int, fmt.noisefloor * sqrt(count)) : 0
push!(worklist, (down, level+1, noisefloor_down, str))
end
end
nothing
end
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