[GHC] #15741: Accept GHCRTS=-N1 when not compiled with -threaded

11 Oct 2018

      #15741: Accept GHCRTS=-N1 when not compiled with -threaded
-------------------------------------+-------------------------------------
           Reporter:  lspitzner      |             Owner:  (none)
               Type:  feature        |            Status:  new
  request                            |
           Priority:  normal         |         Milestone:
          Component:  Runtime        |           Version:  8.6.1
  System                             |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 current behaviour:

 {{{
...
ghc Main.hs -o test
./test +RTS -N1
 test: the flag -N1 requires the program to be built with -threaded
 [blah blah]
 }}}
requested:

 {{{
...
ghc Main.hs -o test
./test +RTS -N1
 hello world
 }}}
Motivation: In certain environments, threaded is bad idea due to resource
 constraints even when multiple capabilities are available, because
 resident memory can increase with parallel execution. Slapping GHCRTS=-N1
 onto those environments would be nice, but breaks for things not compiled
 with -threaded.

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/15741
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