#12136: SIGABRT on right-shift operation against long negative integer
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Reporter: khibino | Owner:
Type: bug | Status: patch
Priority: high | Milestone:
Component: Core Libraries | Version: 8.0.1
Resolution: | Keywords:
Operating System: Linux | Architecture: x86_64 (amd64)
Type of failure: Runtime crash | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Rev(s): D2998
Wiki Page: |
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Comment (by Ben Gamari ):
In [changeset:"06b9561a2f10de68cc14b68a9bfa7617c0019bd9/ghc" 06b9561/ghc]:
{{{
#!CommitTicketReference repository="ghc"
revision="06b9561a2f10de68cc14b68a9bfa7617c0019bd9"
Fix the right-shift operation for negative big integers (fixes #12136)
In `x shiftR y`, any of the following conditions cause an abort:
- `x` is a negative big integer
- The size of `x` and `y` is a multiple of `GMP_NUMB_BITS`
- The bit of the absolute value of `x` is filled with `1`
For example:
Assuming `GMP_NUMB_BITS = 2`, the processing of `-15 shiftR 2` is as
follows:
1. -15 = -1111 (twos complement: 10001)
2. right shift 2 (as a positive number) -> 0011
3. Due to the shift larger than GMP_NUMB_BITS, the size of the
destination is decreasing (2bit) -> 11
4. Add 1, and get carry: (1) 00
5. abort
I fixed it that the destination size does not decrease in such a case.
Test Plan: I tested the specific case being reported.
Reviewers: goldfire, austin, hvr, bgamari, rwbarton
Reviewed By: bgamari, rwbarton
Subscribers: mpickering, rwbarton, thomie
Differential Revision: https://phabricator.haskell.org/D2998
GHC Trac Issues: #12136
}}}
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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12136#comment:5
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