[GHC] #14171: STM causes program to suddenly exit

[GHC]

#14171: STM causes program to suddenly exit
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        Reporter:  MichaelBurge   |                Owner:  bgamari
            Type:  bug            |               Status:  patch
        Priority:  highest        |            Milestone:  8.4.1
       Component:  libraries/stm  |              Version:  8.2.1
      Resolution:                 |             Keywords:
Operating System:  Linux          |         Architecture:  Unknown/Multiple
 Type of failure:  Runtime crash  |            Test Case:
      Blocked By:                 |             Blocking:
 Related Tickets:  #8091          |  Differential Rev(s):  Phab:D3919
       Wiki Page:                 |
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Comment (by Ben Gamari <ben@…>):

 In [changeset:"10a1a4781c646f81ca9e2ef7a2585df2cbe3a014/ghc" 10a1a47/ghc]:
 {{{
 #!CommitTicketReference repository="ghc"
 revision="10a1a4781c646f81ca9e2ef7a2585df2cbe3a014"
 Model divergence of retry# as ThrowsExn, not Diverges

 The demand signature of the retry# primop previously had a Diverges
 result.  However, this caused the demand analyser to conclude that a
 program of the shape,

     catchRetry# (... >> retry#)

 would diverge. Of course, this is plainly wrong; catchRetry#'s sole
 reason to exist is to "catch" the "exception" thrown by retry#. While
 catchRetry#'s demand signature correctly had the ExnStr flag set on its
 first argument, indicating that it should catch divergence, the logic
 associated with this flag doesn't apply to Diverges results. This
 resulted in #14171.

 The solution here is to treat the divergence of retry# as an exception.
 Namely, give it a result type of ThrowsExn rather than Diverges.

 Updates stm submodule for tests.

 Test Plan: Validate with T14171

 Reviewers: simonpj, austin

 Subscribers: rwbarton, thomie

 GHC Trac Issues: #14171, #8091

 Differential Revision: https://phabricator.haskell.org/D3919
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14171#comment:7>
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