From ff492f9bb6641bf65a55f8ff7b68d1604499832f Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Fri, 3 Jul 2015 12:40:26 -0600
Subject: [PATCH] add comments on how page alisngment

---
 racket/src/racket/gc2/vm.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/racket/src/racket/gc2/vm.c b/racket/src/racket/gc2/vm.c
index f5f3b05990..7a096a8162 100644
--- a/racket/src/racket/gc2/vm.c
+++ b/racket/src/racket/gc2/vm.c
@@ -17,7 +17,7 @@ enum {
 };
 
 #if defined(_WIN32) || defined(__CYGWIN32__)
-/* No block cache or alloc cache */
+/* No block cache or alloc cache; relies on APAGE_SIZE matching allocator's alignment */
 #elif defined(OSKIT)
 # define OS_ALLOCATOR_NEEDS_ALIGNMENT
 #elif defined(MZ_USE_PLACES) || defined(PREFER_MMAP_LARGE_BLOCKS)
@@ -30,6 +30,10 @@ enum {
 # define USE_ALLOC_CACHE
 #endif
 
+/* Either USE_ALLOC_CACHE or OS_ALLOCATOR_NEEDS_ALIGNMENT must be
+   enabled, unless the lower-level allocator's alignment matches
+   APAGE_SIZE. */
+
 struct AllocCacheBlock;
 struct BlockCache;
 typedef struct MMU {
@@ -78,7 +82,7 @@ static inline size_t mmu_round_up_to_os_page_size(MMU *mmu, size_t len) {
 
 static inline void mmu_assert_os_page_aligned(MMU *mmu, size_t p) {
   if (p & (mmu->os_pagesize - 1)) {
-    printf("address or size is not OS PAGE ALIGNED!!!!");
+    GCPRINT(GCOUTF, "address or size is not page-aligned\n");
     abort();
   }
 }