Fix a few GCC warnings

GCC 8 now generates warnings for incompatible function pointer casts
[-Werror=cast-function-type]. Apparently there are a few of those in rts
code, which makes `./validate` unhappy (since we compile with `-Werror`)

This commit tries to fix these issues by changing the functions to have
the correct type (and, if necessary, moving the casts into those
functions).

For instance, hash/comparison function are declared (`Hash.h`) to take
`StgWord` but we want to use `StgWord64[2]` in `StaticPtrTable.c`.
Instead of casting the function pointers, we can cast the `StgWord`
parameter to `StgWord*`. I think this should be ok since `StgWord`
should be the same size as a pointer.

Signed-off-by: Michal Terepeta <michal.terepeta@gmail.com>

Test Plan: ./validate

Reviewers: bgamari, erikd, simonmar

Reviewed By: bgamari

Subscribers: rwbarton, thomie, carter

Differential Revision: https://phabricator.haskell.org/D4673

1 files changed, 8 insertions, 7 deletions

diff --git a/rts/StaticPtrTable.c b/rts/StaticPtrTable.c
index 5d2737a262..7711377d7f 100644
--- a/rts/StaticPtrTable.c
+++ b/rts/StaticPtrTable.c
@@ -21,23 +21,24 @@ static Mutex spt_lock;
 #endif
 
 /// Hash function for the SPT.
-static int hashFingerprint(HashTable *table, StgWord64 key[2]) {
+static int hashFingerprint(const HashTable *table, StgWord key) {
+  const StgWord64* ptr = (StgWord64*) key;
   // Take half of the key to compute the hash.
-  return hashWord(table, (StgWord)key[1]);
+  return hashWord(table, *(ptr + 1));
 }
 
 /// Comparison function for the SPT.
-static int compareFingerprint(StgWord64 ptra[2], StgWord64 ptrb[2]) {
-  return ptra[0] == ptrb[0] && ptra[1] == ptrb[1];
+static int compareFingerprint(StgWord a, StgWord b) {
+  const StgWord64* ptra = (StgWord64*) a;
+  const StgWord64* ptrb = (StgWord64*) b;
+  return *ptra == *ptrb && *(ptra + 1) == *(ptrb + 1);
 }
 
 void hs_spt_insert_stableptr(StgWord64 key[2], StgStablePtr *entry) {
   // hs_spt_insert is called from constructor functions, so
   // the SPT needs to be initialized here.
   if (spt == NULL) {
-    spt = allocHashTable_( (HashFunction *)hashFingerprint
-                         , (CompareFunction *)compareFingerprint
-                         );
+    spt = allocHashTable_(hashFingerprint, compareFingerprint);
 #if defined(THREADED_RTS)
     initMutex(&spt_lock);
 #endif