[ET Trac] [Einstein Toolkit] #1571: incorrect use of CCTK_BUILTIN_UNREACHABLE in Carpet

[Einstein Toolkit]

#1571: incorrect use of CCTK_BUILTIN_UNREACHABLE in Carpet
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 Reporter:  rhaas   |       Owner:  eschnett           
     Type:  defect  |      Status:  new                
 Priority:  major   |   Milestone:                     
Component:  Carpet  |     Version:  development version
 Keywords:          |  
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 Carpet in commit fc35c561a049d905763de37d60690fc15473d65d "CarpetLib: Some
 harmless code cleanup" (sic) replaced some assert(0) by
 CCTK_BUILTIN_UNREACHABLE().

 One of those (in the switch in transfer_p_r in line 730 of data.cc) was
 just found by Zach Etienne to cause segfaults if one does not properly add
 a new interpolation operator.

 The difference is that CCTK_BUILTIN_UNREACHABLE() tells the compiler that
 a given line of code will never be reached thus the compiler can optimize
 it away. assert(0) on the other hand makes no such statement, it just
 aborts if it is reached. This error is compiler dependent since
 CCTK_BUILTIN_UNREACHABLE() expands to CCTK_Abort(0,1) unless the compiler
 supports __builtin_unreachable.

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Ticket URL: <https://trac.einsteintoolkit.org/ticket/1571>
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