Adding null initializations

src/racket/gc/alloc.c

@@ -557,7 +557,7 @@ void GC_set_fl_marks(ptr_t q)
 {
    ptr_t p;
    struct hblk * h, * last_h = 0;
-   hdr *hhdr;  /* gcc "might be uninitialized" warning is bogus. */
+   hdr *hhdr = NULL;
    IF_PER_OBJ(size_t sz;)
    unsigned bit_no;
 
@@ -598,8 +598,8 @@ void GC_clear_fl_marks(ptr_t q)
 {
    ptr_t p;
    struct hblk * h, * last_h = 0;
-   hdr *hhdr;
+   hdr *hhdr = NULL;
-   size_t sz;
+   size_t sz = 0;
    unsigned bit_no;
 
    for (p = q; p != 0; p = obj_link(p)){

src/racket/gc/darwin_stop_world.c

@@ -32,7 +32,7 @@ typedef struct StackFrame {
 
 unsigned long FindTopOfStack(unsigned long stack_start)
 {
-  StackFrame	*frame;
+  StackFrame	*frame = NULL;
 
   if (stack_start == 0) {
 # ifdef POWERPC

src/racket/gc/dbg_mlc.c

@@ -759,7 +759,7 @@ void * GC_debug_realloc(void * p, size_t lb, GC_EXTRA_PARAMS)
 {
     void * base = GC_base(p);
     ptr_t clobbered;
-    void * result;
+    void * result = NULL;
     size_t copy_sz = lb;
     size_t old_sz;
     hdr * hhdr;

src/racket/gc/finalize.c

@@ -897,7 +897,7 @@ int GC_invoke_finalizers()
     static int doing = 0; /* PLTSCHEME */
     struct finalizable_object * curr_fo;
     int count = 0;
-    word bytes_freed_before;
+    word bytes_freed_before = 0;
     DCL_LOCK_STATE;
 
     /* PLTSCHEME: don't allow nested finalizations */

src/racket/gc/mark.c

@@ -620,8 +620,8 @@ mse * GC_mark_from(mse *mark_stack_top, mse *mark_stack, mse *mark_stack_limit)
   signed_word credit = HBLKSIZE;  /* Remaining credit for marking work	*/
   ptr_t current_p;	/* Pointer to current candidate ptr.	*/
   word current;	/* Candidate pointer.			*/
-  ptr_t limit;	/* (Incl) limit of current candidate 	*/
+  ptr_t limit = NULL;	/* (Incl) limit of current candidate 	*/
-  				/* range				*/
+						/* range				*/
   word descr;
   ptr_t greatest_ha = GC_greatest_plausible_heap_addr;
   ptr_t least_ha = GC_least_plausible_heap_addr;