Fix all address-of-dummy operations by using GC_approx_sp() instead

(previous commit 'd6acbda' has not solved this problem)

* alloc.c (min_bytes_allocd, GC_stopped_mark): Use GC_approx_sp()
instead of "&dummy"; remove 'dummy' local variable.
* dyn_load.c (GC_cond_add_roots): Likewise.
* misc.c (GC_init): Likewise.
* os_dep.c (GC_get_stack_base, GC_get_main_stack_base): Likewise.
* pthread_stop_world.c (GC_suspend_handler_inner,
nacl_pre_syscall_hook, __nacl_suspend_thread_if_needed): Likewise.
* pthread_support.c (GC_thr_init): Likewise.
* ptr_chck.c (GC_on_stack): Likewise.
* win32_threads.c (GC_push_stack_for): Likewise.
* misc.c (GC_clear_stack_inner): Store address of volatile 'dummy'
local array (i.e. 'sp' value) to its first element (and use it in the
comparison of addresses) to prevent any harmful optimizations as C
officially disallows comparisons of pointers to different objects
(e.g., some Mac OS X clang releases might turn a conditional
expression that uses 'dummy' address into a constant); update comment.
* misc.c (GC_call_with_stack_base): Use "&base" instead of "&dummy"
(it is safe to use address of base here); remove dummy variable.
* os_dep.c (currently_updating): Change type from "word" to "int*".
* os_dep.c (async_set_pht_entry_from_index): Remove volatile and casts
for 'update_dummy' local variable.
* tools/setjmp_t.c (main): Define volatile 'sp' local variable, store
its address to it and use it instead of "&dummy"; remove 'dummy' local
variable.

1 files changed, 5 insertions, 4 deletions

diff --git a/tools/setjmp_t.c b/tools/setjmp_t.c
index 801e6a58..1d9a1ad0 100644
--- a/tools/setjmp_t.c
+++ b/tools/setjmp_t.c
@@ -69,22 +69,23 @@ int * nested_sp(void)
 
 int main(void)
 {
-    volatile int dummy;
+    volatile word sp;
     long ps = GETPAGESIZE();
     jmp_buf b;
     register int x = (int)strlen("a");  /* 1, slightly disguised */
     static int y = 0;
 
+    sp = (word)(&sp);
     printf("This appears to be a %s running %s\n", MACH_TYPE, OS_TYPE);
-    if ((word)nested_sp() < (word)(&dummy)) {
+    if ((word)nested_sp() < sp) {
       printf("Stack appears to grow down, which is the default.\n");
       printf("A good guess for STACKBOTTOM on this machine is 0x%lx.\n",
-             ((unsigned long)(word)(&dummy) + ps) & ~(ps-1));
+             ((unsigned long)sp + ps) & ~(ps-1));
     } else {
       printf("Stack appears to grow up.\n");
       printf("Define STACK_GROWS_UP in gc_private.h\n");
       printf("A good guess for STACKBOTTOM on this machine is 0x%lx.\n",
-             ((unsigned long)(word)(&dummy) + ps) & ~(ps-1));
+             ((unsigned long)sp + ps) & ~(ps-1));
     }
     printf("Note that this may vary between machines of ostensibly\n");
     printf("the same architecture (e.g. Sun 3/50s and 3/80s).\n");