Array max size auditing and fixes#6671
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headius merged 5 commits intojruby:jruby-9.2from May 13, 2021
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This also reduces the fallback maximum to Integer.MAX_VALUE - 2, which seems to be the actual effective size for allocating a new array. See jruby#6670.
headius
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Hmm... so it turns out this effective max array size varies across VMs. As pointed out in some answers here, the OpenJDK ArrayList impl uses MAX_VALUE - 8 to be safe, but there does not appear to be any way to query for the actual effective maximum. We may want to make our max also MAX_VALUE - 8 since that would correspond to a 64-bit pointer alignment. |
Based on explorations for jruby#6670 we found that the effective max array size is actually Integer.MAX_VALUE - 2, so this localizes the multiplication logic and uses that limit as the upper bound. $ jruby -w -e 'foo = "x" * 2147483645; p :ok' :ok $ jruby -w -e 'foo = "x" * 2147483646; p :ok' ArgumentError: argument too big * at org/jruby/RubyString.java:1197 <main> at -e:1
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The array size maximum from AbstractCollection (mentioned in the SO answers above) appears to have been refactored into a utility similar to what we have in this PR: openjdk/jdk@218204b#diff-62a6afd2b76188557fb1b7ccabcfd8398d08eec42983af0c562ef72a588324bf I think it is probably appropriate for us to use |
See refactoring that occurred in OpenJDK here, normalizing many array-allocating paths to MAX - 8: openjdk/jdk@218204b#diff-62a6afd2b76188557fb1b7ccabcfd8398d08eec42983af0c562ef72a588324bf
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This is a follow-up to #6670 that audits other locations we allocate arrays.