Code refactoring of Emscripten platform support (single-threaded)

* alloc.c (min_bytes_allocd): Test STACK_NOT_SCANNED macro instead
of __EMSCRIPTEN__ (stack size to scan is zero if STACK_NOT_SCANNED).
* include/private/gcconfig.h (ALIGNMENT): Remove duplicate definition
for _EMSCRIPTEN__.
* include/private/gcconfig.h (STACK_NOT_SCANNED): New macro defined
for __EMSCRIPTEN__ target (in addition to  OS_TYPE, CPP_WORDSZ,
ALIGNMENT, DATASTART, DATAEND).
* mach_dep.c (GC_push_regs): Test STACK_NOT_SCANNED macro instead
of __EMSCRIPTEN__ (push nothing if STACK_NOT_SCANNED).
* mark_rts.c (GC_push_roots): Test STACK_NOT_SCANNED macro instead
of __EMSCRIPTEN__ (do not call GC_push_regs_and_stack if
STACK_NOT_SCANNED); mark cold_gc_frame argument as potentially unused.
* misc.c (GC_clear_stack): Test STACK_NOT_SCANNED macro instead
of __EMSCRIPTEN__ (do not clear stack if STACK_NOT_SCANNED).
* misc.c (GC_clear_stack): Reformat code.

1 files changed, 3 insertions, 5 deletions

diff --git a/alloc.c b/alloc.c
index d8fb954f..2f877fba 100644
--- a/alloc.c
+++ b/alloc.c
@@ -202,15 +202,13 @@ GC_API GC_stop_func GC_CALL GC_get_stop_func(void)
 static word min_bytes_allocd(void)
 {
     word result;
-#   ifdef __EMSCRIPTEN__
+#   ifdef STACK_NOT_SCANNED
       word stack_size = 0;
-#   else 
-#     ifdef STACK_GROWS_UP
+#   elif defined(STACK_GROWS_UP)
       word stack_size = GC_approx_sp() - GC_stackbottom;
             /* GC_stackbottom is used only for a single-threaded case.  */
-#     else
+#   else
       word stack_size = GC_stackbottom - GC_approx_sp();
-#     endif
 #   endif
 
     word total_root_size;       /* includes double stack size,  */