Make forkProcess work with +RTS -N

Consider this experimental for the time being.  There are a lot of
things that could go wrong, but I've verified that at least it works
on the test cases we have.

I also did some API cleanups while I was here.  Previously we had:

Capability * rts_eval (Capability *cap, HaskellObj p, /*out*/HaskellObj *ret);

but this API is particularly error-prone: if you forget to discard the
Capability * you passed in and use the return value instead, then
you're in for subtle bugs with +RTS -N later on.  So I changed all
these functions to this form:

void rts_eval (/* inout */ Capability **cap,
               /* in    */ HaskellObj p,
               /* out */   HaskellObj *ret)

It's much harder to use this version incorrectly, because you have to
pass the Capability in by reference.

1 files changed, 1 insertions, 1 deletions

diff --git a/rts/posix/OSThreads.c b/rts/posix/OSThreads.c
index cc3baeb1bb..e25cdc1e81 100644
--- a/rts/posix/OSThreads.c
+++ b/rts/posix/OSThreads.c
@@ -197,7 +197,7 @@ forkOS_createThreadWrapper ( void * entry )
 {
     Capability *cap;
     cap = rts_lock();
-    cap = rts_evalStableIO(cap, (HsStablePtr) entry, NULL);
+    rts_evalStableIO(&cap, (HsStablePtr) entry, NULL);
     taskTimeStamp(myTask());
     rts_unlock(cap);
     return NULL;