Prevent compiler warnings in GC_FindTopOfStack and GC_ports (Darwin)

* darwin_stop_world.c (GC_FindTopOfStack): Initialize "frame" local
variable from "stack_start" unless done via PPC lwz/ld instruction (to
prevent "uninitialized variable use" compiler warning;
add assertion for "stack_start" value; add 'U' suffix to int constant
to prevent comparison of signed and unsigned value.
* os_dep.c (GC_ports): Explicitly initialize "reply" field to zero if
THREADS (to suppress compiler warning on Darwin).

1 files changed, 3 insertions, 0 deletions

diff --git a/os_dep.c b/os_dep.c
index c4058416..03a0ca8d 100644
--- a/os_dep.c
+++ b/os_dep.c
@@ -3900,6 +3900,9 @@ STATIC struct {
     (void (*)(void))catch_exception_raise_state,
     (void (*)(void))catch_exception_raise_state_identity
   },
+# ifdef THREADS
+    0, /* for 'exception' */
+# endif
   0
 };