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Segfault while indexing with infinite Seq #2120

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taboege opened this issue Jul 23, 2018 · 3 comments
Closed

Segfault while indexing with infinite Seq #2120

taboege opened this issue Jul 23, 2018 · 3 comments
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@zoffixznet
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BLOCKER Preventing the next release of rakudo, or just needing attention before the release QAST issues that require working with QAST to fix regression Issue did not exist previously

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@taboege
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taboege commented Jul 23, 2018

The Problem

The following code segfaults using rakudo-moar HEAD via camelia [^1]:

(^10)[2.polymod($_ xx *).map($_ ** *) »%» *] with 1

Interestingly, removing the map (which should produce constant 1) or inlining the with 1 leads to a timeout [^2,3].

On my personal machine with Rakudo-moar 2018.06, it just hangs in all three cases.

Expected Behavior

It should hang as the polymod(1 xx *) produces an infinite list.

Actual Behavior

SIGSEGV, but only when the seemingly useless map and with 1 are left intact.

Environment

  • Works as expected with Rakudo version 2018.06 built on MoarVM version 2018.06,
  • Segfaults with rakudo-moar c47e3681c.

References

[^1] http://colabti.org/irclogger/irclogger_log/perl6?date=2018-07-23#l486
[^2] http://colabti.org/irclogger/irclogger_log/perl6?date=2018-07-23#l504
[^3] http://colabti.org/irclogger/irclogger_log/perl6?date=2018-07-23#l506
@AlexDaniel
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Bisected: (2018-07-09) c2446b0

NQP changes in the bump: Raku/nqp@2018.06-27-gcec76ff79...2018.06-36-g39f1057
Moar changes in the bump: MoarVM/MoarVM@2018.06-103-gaf455397f...2018.06-141-gcae4731

@AlexDaniel AlexDaniel added regression Issue did not exist previously BLOCKER Preventing the next release of rakudo, or just needing attention before the release labels Jul 23, 2018
@zoffixznet
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zoffixznet commented Jul 23, 2018 •
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FWIW, the QAST has two misscoped blocks, so it's pure luck this worked in the past (if it even did)

@zoffixznet zoffixznet added the QAST issues that require working with QAST to fix label Jul 23, 2018
@zoffixznet
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Golf of the scoping issue: {1}() + * with 1

@zoffixznet zoffixznet self-assigned this Jul 23, 2018
zoffixznet added a commit that referenced this issue Jul 23, 2018
@zoffixznet
Fix misscoping of blocks in whatever curries
8549589 
Fixes R#2120 #2120

The migrator in whatever currier is too naive and in the branch
that handles block args assumed QAST::WVal of code would just be
the kid. However, it can also be a kid of the kid, placed in some
other ops, like nqp::call.

Fix by doing more thorough search for blocks to migrate by descending
into the kid. Also, wide the nodes we search to all QAST::Nodes. The
original list of nodes just assumed some nodes can't be @(), but
I think all of them can, actually.
ugexe pushed a commit to Raku/roast that referenced this issue Dec 15, 2018
@zoffixznet @ugexe
Cover SEGV in curries + with
655f561 
Closes rakudo/rakudo#2120 R#2120
Rakudo fix: rakudo/rakudo@85495890d4
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@AlexDaniel @zoffixznet @taboege