How to detect if a program has been compiled using -threaded?

Question

I\'m working on a Haskell daemon that uses POSIX fork/exec together with file locking mechanism. My experiments show that file locks aren\'t inherited during executeFi

Answer 1

There is a value in Control.Concurrent for this, for example:

module Main (main) where

import Control.Concurrent

main :: IO ()
main = print rtsSupportsBoundThreads

And test:

$ ghc -fforce-recomp Test.hs; ./Test
[1 of 1] Compiling Main             ( Test.hs, Test.o )
Linking Test ...
False
$ ghc -fforce-recomp -threaded Test.hs; ./Test
[1 of 1] Compiling Main             ( Test.hs, Test.o )
Linking Test ...
True

And it's C-part source code:

HsBool
rtsSupportsBoundThreads(void)
{
#if defined(THREADED_RTS)
  return HS_BOOL_TRUE;
#else
  return HS_BOOL_FALSE;
#endif
}