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

5 files changed, 16 insertions, 13 deletions

diff --git a/rts/Hash.c b/rts/Hash.c
index b9a3cf6f33..658187b944 100644
--- a/rts/Hash.c
+++ b/rts/Hash.c
@@ -77,8 +77,9 @@ hashWord(const HashTable *table, StgWord key)
 }
 
 int
-hashStr(const HashTable *table, char *key)
+hashStr(const HashTable *table, StgWord w)
 {
+    const char *key = (char*) w;
 #ifdef x86_64_HOST_ARCH
     StgWord h = XXH64 (key, strlen(key), 1048583);
 #else
@@ -440,8 +441,7 @@ allocHashTable(void)
 HashTable *
 allocStrHashTable(void)
 {
-    return allocHashTable_((HashFunction *)hashStr,
-                           (CompareFunction *)compareStr);
+    return allocHashTable_(hashStr, compareStr);
 }
 
 void
diff --git a/rts/Hash.h b/rts/Hash.h
index 1dde314d0e..be388fb62f 100644
--- a/rts/Hash.h
+++ b/rts/Hash.h
@@ -56,7 +56,7 @@ typedef int HashFunction(const HashTable *table, StgWord key);
 typedef int CompareFunction(StgWord key1, StgWord key2);
 HashTable * allocHashTable_(HashFunction *hash, CompareFunction *compare);
 int hashWord(const HashTable *table, StgWord key);
-int hashStr(const HashTable *table, char *key);
+int hashStr(const HashTable *table, StgWord key);
 
 /* Freeing hash tables
  */
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
diff --git a/rts/Task.c b/rts/Task.c
index 758ae10ffc..ac86311844 100644
--- a/rts/Task.c
+++ b/rts/Task.c
@@ -416,7 +416,7 @@ workerTaskStop (Task *task)
 
 #if defined(THREADED_RTS)
 
-static void OSThreadProcAttr
+static void* OSThreadProcAttr
 workerStart(Task *task)
 {
     Capability *cap;
@@ -442,6 +442,8 @@ workerStart(Task *task)
     traceTaskCreate(task, cap);
 
     scheduleWorker(cap,task);
+
+    return NULL;
 }
 
 /* N.B. must take all_tasks_mutex */
diff --git a/rts/posix/OSThreads.c b/rts/posix/OSThreads.c
index 9cf42aa246..7dcf0eed15 100644
--- a/rts/posix/OSThreads.c
+++ b/rts/posix/OSThreads.c
@@ -134,7 +134,7 @@ int
 createOSThread (OSThreadId* pId, char *name STG_UNUSED,
                 OSThreadProc *startProc, void *param)
 {
-  int result = pthread_create(pId, NULL, (void *(*)(void *))startProc, param);
+  int result = pthread_create(pId, NULL, startProc, param);
   if (!result) {
     pthread_detach(*pId);
 #if defined(HAVE_PTHREAD_SETNAME_NP)