[GHC] #14972: MacOS panic on TH

[GHC]

#14972: MacOS panic on TH
-------------------------------------+-------------------------------------
        Reporter:  harpocrates       |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.4.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
-------------------------------------+-------------------------------------

Comment (by ezyang):

 I've diagnosed the proximate cause. In the failing version of the
 compiler, an inplace build creates a `gmp` directory in `libraries
 /integer-gmp/dist-install/build/`:

 {{{
 MacBook-Pro-97:ghc-quick1 ezyang$ ls libraries/integer-gmp/dist-
 install/build/
 GHC                                             gmp
 HSinteger-gmp-1.0.1.0.o                         include
 autogen                                         integer-gmp.buildinfo
 cbits                                           libHSinteger-
 gmp-1.0.1.0-ghc8.5.20180331.dylib
 config.log                                      libHSinteger-gmp-1.0.1.0.a
 config.status
 }}}

 Unfortuantely, this changes the behavior of our print file name
 invocation:

 {{{
 MacBook-Pro-97:ghc-quick1 ezyang$ gcc -fno-stack-protector
 -DTABLES_NEXT_TO_CODE -B/Users/ezyang/Dev/ghc-quick1/libraries/integer-gmp
 /dist-install/build --print-file-name gmp
 /Users/ezyang/Dev/ghc-quick1/libraries/integer-gmp/dist-install/build/gmp
 }}}

 This should return `gmp`. When it returns a file path, we attempt to open
 this location, which clearly will not work:

 {{{
 *** gcc:
 gcc -fno-stack-protector -DTABLES_NEXT_TO_CODE -B/Users/ezyang/Dev/ghc-
 quick1/libraries/integer-gmp/dist-install/build --print-file-name gmp

 addLibrarySearchPath: dll_path = `/Users/ezyang/Dev/ghc-quick1/libraries
 /integer-gmp/dist-install/build'
 Loading package integer-gmp-1.0.1.0 ... addDLL: dll_name =
 '/Users/ezyang/Dev/ghc-quick1/libraries/integer-gmp/dist-install/build
 /libHSinteger-gmp-1.0.1.0-ghc8.5.20180331.dylib'
 internal_dlopen: dll_name = '/Users/ezyang/Dev/ghc-quick1/libraries
 /integer-gmp/dist-install/build/libHSinteger-
 gmp-1.0.1.0-ghc8.5.20180331.dylib'
 loadArchive: start
 loadArchive: Loading archive `/Users/ezyang/Dev/ghc-quick1/libraries
 /integer-gmp/dist-install/build/gmp'
 ghc-stage2: loadArchive: Failed reading header from `/Users/ezyang/Dev
 /ghc-quick1/libraries/integer-gmp/dist-install/build/gmp'
 loadArchive: done
 *** Deleting temp files:
 Deleting:
 *** Deleting temp dirs:
 Deleting:
 ghc-stage2: panic! (the 'impossible' happened)
   (GHC version 8.5.20180331 for x86_64-apple-darwin):
         loadArchive "/Users/ezyang/Dev/ghc-quick1/libraries/integer-gmp
 /dist-install/build/gmp": failed

 Please report this as a GHC bug:  http://www.haskell.org/ghc/reportabug
 }}}

 I hazard some change in Cabal caused the 'gmp' directory to be created.
 Not entirely sure what the correct fix is yet.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14972#comment:7>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler