[GHC] #13477: Turn cIntegerLibraryType into a dynflag

[GHC]

#13477: Turn cIntegerLibraryType into a dynflag
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        Reporter:  nomeata           |                Owner:  (none)
            Type:  task              |               Status:  new
        Priority:  low               |            Milestone:
       Component:  GHC API           |              Version:  8.1
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
                                     |  Unknown/Multiple
 Type of failure:  None/Unknown      |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by nomeata):

 It keeps happening that when I want to file a bug report, I find that I
 have already filed it…

 A `ghc`-the-library that allows users to choose the integer library they
 want would be great. For example asterius, a WebAssembly backend in the
 making, would then have one reason less to build on a patched `ghc` (see
 https://tweag.github.io/asterius/building/)

 There are two issues:
  * Using `S#` if `integer-gmp` is used. Can easily be made dependent on
 the `DynFlags`.
  * Using the right unit id in `gHC_INTEGER_TYPE`, which is used in all
 kind of `…Name` symbols, which are used in other top-level definitions
 like `CoreRules`. Would be more invasive to make that dependent on
 `DynFlags`.

 I wonder if maybe GHC should just assume that the unit name is `integer`,
 and the build script of `integer-gmp` resp. `integer-simple` passes
 `-this-unit-id integer` instead? What would break in this simple model?

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13477#comment:2>
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