[GHC] #15262: TH splice containing numeric literal 0 causes heap overflow while cross-compiling

11 Jun 2018

      #15262: TH splice containing numeric literal 0 causes heap overflow while cross-
compiling
-------------------------------------+-------------------------------------
           Reporter:  howtonotwin    |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:  8.6.1
          Component:  Compiler       |           Version:  8.5
           Keywords:                 |  Operating System:  MacOS X
       Architecture:                 |   Type of failure:  Compile-time
  Unknown/Multiple                   |  crash or panic
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 Tested off commit `9976bed24dda9449ac2e3e95fb4bf8b379114a28`, running on
 macOS 10.13.5, trying to compile for iOS.

 1. Compile a GHC that cross compiles to `x86_64-apple-ios` (i.e. with
 `./configure --build=x86_64-apple-darwin --host=x86_64-apple-darwin
 --target=x86_64-apple-ios; make`).
 2. Compile a `ghc-iserv` that can run on the build system (i.e. with
 `./configure; cd utils/iserv; make`)
 3. Try to cross-compile the following file (i.e `x86_64-apple-ios-ghc
 -fexternal-interpreter -pgmi=path/to/ghc-iserv T.hs`):
    {{{#!hs
    {-# LANGUAGE TemplateHaskell #-}
    module T where
    $([d| zero = 0 |])
    }}}

 Expected: Compiles fine.

 Actual:

 {{{
 [1 of 1] Compiling T                ( T.hs, T.o )

 T.hs:1:1: error:
     Exception when trying to run compile-time code:
       heap overflow
     Code: [d| zero = 0 |]
   |
 1 | {-# LANGUAGE TemplateHaskell #-}
   | ^
 }}}

 For more fun:

 * This problem appears to only affect the numeric literal `0`.
    * `0.0` is not fine.
    * `1` is fine.
    * `1 - 1` appears to be a workaround.
    * `0.1` is fine.
    * "Burying" the `0` inside another expression is not fine (e.g. `zero =
 [0]`).
    * I can even compile most of `singletons`, and it only chokes when the
 `0` literal first appears (`negate x = 0 - x`).
    * The `0` has to actually appear in the result. (`$(const [d| |] [d|
 zero = 0 |])` is fine.)
    * `0#` is not fine.
 * This problem only appears when cross-compiling. If I complete the build
 of the native GHC above and use it instead of the cross-compiler but still
 use `-fexternal-interpreter`, everything is fine.
 * Moving the declaration outside of the TH brackets is fine.

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15262
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