diff --git a/pkgs/gui-pkgs/gui-lib/mred/private/wx/gtk/pixbuf.rkt b/pkgs/gui-pkgs/gui-lib/mred/private/wx/gtk/pixbuf.rkt
index d5c2733c22..c875a4feee 100644
--- a/pkgs/gui-pkgs/gui-lib/mred/private/wx/gtk/pixbuf.rkt
+++ b/pkgs/gui-pkgs/gui-lib/mred/private/wx/gtk/pixbuf.rkt
@@ -37,8 +37,8 @@
   #:wrap (allocator release-pixbuf))
 
 (define-gdk gdk_cairo_set_source_pixbuf (_fun _cairo_t _GdkPixbuf _double* _double* -> _void))
-(define-gdk gdk_pixbuf_get_width (_fun _GdkPixbuf -> _int))
-(define-gdk gdk_pixbuf_get_height (_fun _GdkPixbuf -> _int))
+(define-gdk_pixbuf gdk_pixbuf_get_width (_fun _GdkPixbuf -> _int))
+(define-gdk_pixbuf gdk_pixbuf_get_height (_fun _GdkPixbuf -> _int))
 
 (define free-it (ffi-callback free
                               (list _pointer)
diff --git a/pkgs/gui-pkgs/gui-lib/mred/private/wx/gtk/win32.rkt b/pkgs/gui-pkgs/gui-lib/mred/private/wx/gtk/win32.rkt
index a741489994..2ca6e23d77 100644
--- a/pkgs/gui-pkgs/gui-lib/mred/private/wx/gtk/win32.rkt
+++ b/pkgs/gui-pkgs/gui-lib/mred/private/wx/gtk/win32.rkt
@@ -1,6 +1,7 @@
 #lang racket/base
 (require ffi/unsafe
          ffi/unsafe/define
+         ffi/winapi
          "utils.rkt")
 
 (provide gdk_win32_drawable_get_handle
@@ -20,7 +21,7 @@
 (define-gdk gdk_win32_drawable_get_handle (_fun _GdkDrawable -> _pointer)
   #:make-fail make-not-available)
 
-(define-user32 GetDC (_fun #:abi 'stdcall _pointer -> _pointer)
+(define-user32 GetDC (_fun #:abi winapi _pointer -> _pointer)
   #:make-fail make-not-available)
-(define-user32 ReleaseDC (_fun #:abi 'stdcall _pointer -> _void)
+(define-user32 ReleaseDC (_fun #:abi winapi _pointer -> _void)
   #:make-fail make-not-available)
diff --git a/racket/collects/compiler/private/xform.rkt b/racket/collects/compiler/private/xform.rkt
index f609110066..ff36e83354 100644
--- a/racket/collects/compiler/private/xform.rkt
+++ b/racket/collects/compiler/private/xform.rkt
@@ -886,8 +886,8 @@
                ;; they either take one argument or no pointer arguments.
                ;; So we can ignore them:
                
-               
                __get_errno_ptr ; QNX preprocesses errno to __get_errno_ptr
+               __getreent ; Cygwin
 
                strlen cos cosl sin sinl exp expl pow powl log logl sqrt sqrtl atan2 atan2l
                isnan isinf fpclass _fpclass __fpclassify __fpclassifyf __fpclassifyl
diff --git a/racket/collects/ffi/winapi.rkt b/racket/collects/ffi/winapi.rkt
index c1d3de4076..f0a0987ac2 100644
--- a/racket/collects/ffi/winapi.rkt
+++ b/racket/collects/ffi/winapi.rkt
@@ -6,4 +6,7 @@
   (and (eq? 'windows (system-type))
        (equal? "win32\\x86_64" (path->string (system-library-subpath #f)))))
 
-(define winapi (if win64? 'default 'stdcall))
+(define winapi (if (or win64?
+                       (not (eq? 'windows (system-type))))
+                   'default
+                   'stdcall))
diff --git a/racket/src/README b/racket/src/README
index ebe1d2e2fd..0a3fc3e3b7 100644
--- a/racket/src/README
+++ b/racket/src/README
@@ -31,11 +31,10 @@ The result is a Windows-style build, but without MzCOM. If you are using
 a variant of MinGW without "libdelayimp.a", get the implementation of
 "delayimp.c" from MinGW-w64 and compile it to "libdelayimp.a".
 
-To compile with Cygwin tools, follow the Unix instructions below, and be
-sure to configure with `--enable-shared'.  The result is a Unix-style
-build, not a Windows-style build (e.g., Racket's `system-type' procedure
-returns 'unix, not 'windows, and `racket/gui' uses Gtk instead of
-Win32).
+To compile with Cygwin tools, follow the Unix instructions below.  The
+result is a Unix-style build, not a Windows-style build (e.g.,
+Racket's `system-type' procedure returns 'unix, not 'windows, and
+`racket/gui' uses Gtk instead of Win32).
 
 Beware that MinGW/Cygwin builds different from the MSVC build when
 SSE-based floating-point math is enabled in the C compiler. In that
diff --git a/racket/src/configure b/racket/src/configure
index 0d91837c8b..48fa5f90a6 100755
--- a/racket/src/configure
+++ b/racket/src/configure
@@ -4584,7 +4584,6 @@ $as_echo "#define HAVE_STDINT_H 1" >>confdefs.h
     esac
     ;;
   cygwin*)
-    enable_cgcdefault="yes"
     MZINSTALLTARGET=unix-cygwin-install
     if test "${enable_shared}" = "yes" ; then
       ar_libtool_no_undefined=" -no-undefined"
diff --git a/racket/src/foreign/foreign.c b/racket/src/foreign/foreign.c
index b5be78debf..5babfa216a 100644
--- a/racket/src/foreign/foreign.c
+++ b/racket/src/foreign/foreign.c
@@ -267,6 +267,9 @@ static Scheme_Object *foreign_ffi_lib(int argc, Scheme_Object *argv[])
 #   ifdef __ANDROID__
     if (!name) handle = RTLD_DEFAULT; else
 #   endif /* __ANDROID__ */
+#   ifdef __CYGWIN32__
+    if (!name) { handle = RTLD_DEFAULT; null_ok = 1; } else
+#   endif /* __CYGWIN32__ */
     handle = dlopen(name, RTLD_NOW | (as_global ? RTLD_GLOBAL : RTLD_LOCAL));
 #   endif /* WINDOWS_DYNAMIC_LOAD */
     if (handle == NULL && !null_ok) {
diff --git a/racket/src/foreign/foreign.rktc b/racket/src/foreign/foreign.rktc
index f1ded27583..e67332c168 100755
--- a/racket/src/foreign/foreign.rktc
+++ b/racket/src/foreign/foreign.rktc
@@ -235,6 +235,7 @@ THREAD_LOCAL_DECL(static Scheme_Hash_Table *opened_libs);
         handle = LoadLibraryW(WIDE_PATH(name));
     }{
       @@IFDEF{__ANDROID__}{if (!name) handle = RTLD_DEFAULT; else}
+      @@IFDEF{__CYGWIN32__}{if (!name) { handle = RTLD_DEFAULT; null_ok = 1; } else}
       handle = dlopen(name, RTLD_NOW | (as_global ? RTLD_GLOBAL : RTLD_LOCAL));
     }
     if (handle == NULL && !null_ok) {
diff --git a/racket/src/racket/configure.ac b/racket/src/racket/configure.ac
index 71884cdd86..2895aa1f38 100644
--- a/racket/src/racket/configure.ac
+++ b/racket/src/racket/configure.ac
@@ -718,7 +718,6 @@ case "$host_os" in
     esac
     ;;    
   cygwin*)
-    enable_cgcdefault="yes"
     MZINSTALLTARGET=unix-cygwin-install
     if test "${enable_shared}" = "yes" ; then
       ar_libtool_no_undefined=" -no-undefined"
diff --git a/racket/src/racket/gc2/gc2_obj.h b/racket/src/racket/gc2/gc2_obj.h
index 5261cbe327..6061e8ab50 100644
--- a/racket/src/racket/gc2/gc2_obj.h
+++ b/racket/src/racket/gc2/gc2_obj.h
@@ -3,7 +3,7 @@
 
 #if defined(MZ_PRECISE_GC) && !defined(USE_COMPACT_3M_GC)
 
-#if defined(_WIN32) || defined(MZ_USE_LARGE_PAGE_SIZE)
+#if defined(_WIN32) || defined(__CYGWIN32__) || defined(MZ_USE_LARGE_PAGE_SIZE)
 # define LOG_APAGE_SIZE 16
 #else
 # define LOG_APAGE_SIZE 14
diff --git a/racket/src/racket/gc2/page_range.c b/racket/src/racket/gc2/page_range.c
index 218fb7c2a4..a4e71c7d58 100644
--- a/racket/src/racket/gc2/page_range.c
+++ b/racket/src/racket/gc2/page_range.c
@@ -7,7 +7,7 @@
     os_protect_pages
 */
 
-#ifdef _WIN32
+#if defined(_WIN32) || defined(__CYGWIN32__)
 
 /* VirtualProtect can be used only on pages allocated at the same
    time, so we can't collapse ranges. */
diff --git a/racket/src/racket/gc2/sighand.c b/racket/src/racket/gc2/sighand.c
index dff2fd510f..6c46acda45 100644
--- a/racket/src/racket/gc2/sighand.c
+++ b/racket/src/racket/gc2/sighand.c
@@ -162,7 +162,10 @@ void fault_handler(int sn, struct siginfo *si, void *ctx)
 #endif
 
 /* ========== Windows signal handler ========== */
-#if defined(_WIN32)
+#if defined(_WIN32) || defined(__CYGWIN32__)
+# if defined(__CYGWIN32__)
+#  include <windows.h>
+# endif
 LONG WINAPI fault_handler(LPEXCEPTION_POINTERS e) 
 {
   if ((e->ExceptionRecord->ExceptionCode == EXCEPTION_ACCESS_VIOLATION)
diff --git a/racket/src/racket/gc2/vm.c b/racket/src/racket/gc2/vm.c
index 84d46bf10f..55d36b3e90 100644
--- a/racket/src/racket/gc2/vm.c
+++ b/racket/src/racket/gc2/vm.c
@@ -16,8 +16,18 @@ enum {
   MMU_WRITABLE        = 1,
 };
 
-#if (defined(MZ_USE_PLACES) && !defined(_WIN32)) || defined(PREFER_MMAP_LARGE_BLOCKS)
+#if defined(_WIN32) || defined(__CYGWIN32__)
+/* No block cache or alloc cache */
+#elif defined(OSKIT)
+# define OS_ALLOCATOR_NEEDS_ALIGNMENT
+#elif defined(MZ_USE_PLACES) && defined(PREFER_MMAP_LARGE_BLOCKS)
 # define USE_BLOCK_CACHE
+#else
+# define USE_ALLOC_CACHE
+#endif
+
+#ifdef USE_BLOCK_CACHE
+# define USE_ALLOC_CACHE
 #endif
 
 struct AllocCacheBlock;
@@ -25,7 +35,7 @@ struct BlockCache;
 typedef struct MMU {
 #ifdef USE_BLOCK_CACHE
   struct BlockCache *block_cache;
-#elif !( defined(_WIN32) || defined(OSKIT) )
+#elif defined(USE_ALLOC_CACHE)
   struct AllocCacheBlock *alloc_caches[2];
   Page_Range *page_range;
 #endif
@@ -34,16 +44,13 @@ typedef struct MMU {
   NewGC *gc;
 } MMU;
 
-#if !( defined(_WIN32) || defined(OSKIT) )
+#ifdef OS_ALLOCATOR_NEEDS_ALIGNMENT
+static void *os_alloc_aligned_pages(size_t len, size_t alignment, int dirty_ok)
+#else
 static void  *os_alloc_pages(size_t len);
+#endif
 static void   os_free_pages(void *p, size_t len);
 static void   os_protect_pages(void *p, size_t len, int writable);
-#else
-static void  *os_alloc_pages(MMU *mmu, size_t len, size_t alignment, int dirty);
-static void   os_free_pages(MMU *mmu, void *p, size_t len);
-static void   os_protect_pages(void *p, size_t len, int writable);
-static void   os_flush_freed_pages(MMU *mmu);
-#endif
 
 /* provides */
 static inline size_t mmu_get_os_page_size(MMU *mmu) { return mmu->os_pagesize; }
@@ -77,32 +84,29 @@ static inline void mmu_assert_os_page_aligned(MMU *mmu, size_t p) {
 }
 
 #ifdef USE_BLOCK_CACHE
-#include "block_cache.c"
-#include "alloc_cache.c"
-#include "page_range.c"
-#include <unistd.h>
-#elif !( defined(_WIN32) || defined(OSKIT) )
-#include "alloc_cache.c"
-#include "page_range.c"
-#include <unistd.h>
+# include "block_cache.c"
+#endif
+#ifdef USE_ALLOC_CACHE
+# include "alloc_cache.c"
+# include "page_range.c"
+# include <unistd.h>
 #endif
-
 
 static MMU *mmu_create(NewGC *gc) {
   MMU *mmu = ofm_malloc_zero(sizeof(MMU));
   mmu->gc = gc;
 
-#if !( defined(_WIN32) || defined(OSKIT) )
-#ifdef USE_BLOCK_CACHE
+#ifdef USE_ALLOC_CACHE
+# ifdef USE_BLOCK_CACHE
   mmu->block_cache = block_cache_create(mmu);
-#else
+# else
   /* initialization of page_range */
   mmu->page_range = page_range_create();
 
   /* initialization of alloc_cache */
   mmu->alloc_caches[0] = alloc_cache_create();
   mmu->alloc_caches[1] = alloc_cache_create();
-#endif
+# endif
 
   mmu->os_pagesize = getpagesize();
 #else
@@ -116,7 +120,7 @@ static void mmu_free(MMU *mmu) {
   /* printf("MMU ALLOCATED PRE  %li\n", mmu->memory_allocated); */
 #ifdef USE_BLOCK_CACHE
   mmu->memory_allocated += block_cache_free(mmu->block_cache);
-#elif !( defined(_WIN32) || defined(OSKIT) )
+#elif defined(USE_ALLOC_CACHE)
   page_range_free(mmu->page_range);
   mmu->memory_allocated += alloc_cache_free(mmu->alloc_caches[0]);
   mmu->memory_allocated += alloc_cache_free(mmu->alloc_caches[1]);
@@ -129,7 +133,7 @@ static void *mmu_alloc_page(MMU* mmu, size_t len, size_t alignment, int dirty, i
   mmu_assert_os_page_aligned(mmu, len);
 #ifdef USE_BLOCK_CACHE
   return block_cache_alloc_page(mmu->block_cache, len, alignment, dirty, type, expect_mprotect, src_block, &mmu->memory_allocated);
-#elif !( defined(_WIN32) || defined(OSKIT) )
+#elif defined(USE_ALLOC_CACHE)
   /* len = mmu_round_up_to_os_page_size(mmu, len); */
   {
     AllocCacheBlock *alloc_cache = mmu->alloc_caches[!!expect_mprotect];
@@ -137,7 +141,11 @@ static void *mmu_alloc_page(MMU* mmu, size_t len, size_t alignment, int dirty, i
   }
 #else
   mmu->memory_allocated += len;
-  return os_alloc_pages(mmu, len, alignment, dirty);
+# ifdef OS_ALLOCATOR_NEEDS_ALIGNMENT
+  return os_alloc_aligned_pages(len, alignment, dirty);
+#else
+  return os_alloc_pages(len);
+# endif
 #endif
 }
 
@@ -148,7 +156,7 @@ static void mmu_free_page(MMU* mmu, void *p, size_t len, int type, int expect_mp
 #ifdef USE_BLOCK_CACHE
   mmu->memory_allocated += block_cache_free_page(mmu->block_cache, p, len, type, expect_mprotect, src_block,
                                                  originated_here);
-#elif !( defined(_WIN32) || defined(OSKIT) )
+#elif defined(USE_ALLOC_CACHE)
   /* len = mmu_round_up_to_os_page_size(mmu, len); */
   {
     AllocCacheBlock *alloc_cache = mmu->alloc_caches[!!expect_mprotect];
@@ -156,18 +164,16 @@ static void mmu_free_page(MMU* mmu, void *p, size_t len, int type, int expect_mp
   }
 #else
   if (originated_here) mmu->memory_allocated -= len;
-  os_free_pages(mmu, p, len);
+  os_free_pages(p, len);
 #endif
 }
 
 static void mmu_flush_freed_pages(MMU *mmu) {
 #ifdef USE_BLOCK_CACHE
   mmu->memory_allocated += block_cache_flush_freed_pages(mmu->block_cache);
-#elif !( defined(_WIN32) || defined(OSKIT) )
+#elif defined(USE_ALLOC_CACHE)
   mmu->memory_allocated += alloc_cache_flush_freed_pages(mmu->alloc_caches[0]);
   mmu->memory_allocated += alloc_cache_flush_freed_pages(mmu->alloc_caches[1]);
-#elif defined(_WIN32)
-  os_flush_freed_pages(mmu);
 #endif  
 }
 
@@ -195,7 +201,7 @@ static void mmu_queue_protect_range(MMU *mmu, void *p, size_t len, int type, int
   mmu_assert_os_page_aligned(mmu, len);
 #ifdef USE_BLOCK_CACHE
   block_cache_queue_protect_range(mmu->block_cache, p, len, type, writeable, src_block);
-#elif !( defined(_WIN32) || defined(OSKIT) )
+#elif defined(USE_ALLOC_CACHE)
   page_range_add(mmu->page_range, p, len, writeable);
 #else
   os_protect_pages(p, len, writeable);
@@ -213,7 +219,7 @@ static void mmu_queue_write_unprotect_range(MMU *mmu, void *p, size_t len, int t
 static void mmu_flush_write_protect_ranges(MMU *mmu) {
 #ifdef USE_BLOCK_CACHE
   block_cache_flush_protect_ranges(mmu->block_cache, MMU_WRITE_PROTECTED);
-#elif !( defined(_WIN32) || defined(OSKIT) )
+#elif defined(USE_ALLOC_CACHE)
   page_range_flush(mmu->page_range, MMU_WRITE_PROTECTED);
 #endif  
 }
@@ -221,7 +227,7 @@ static void mmu_flush_write_protect_ranges(MMU *mmu) {
 static void mmu_flush_write_unprotect_ranges(MMU *mmu) {
 #ifdef USE_BLOCK_CACHE
   block_cache_flush_protect_ranges(mmu->block_cache, MMU_WRITABLE);
-#elif !( defined(_WIN32) || defined(OSKIT) )
+#elif defined(USE_ALLOC_CACHE)
   page_range_flush(mmu->page_range, MMU_WRITABLE);
 #endif  
 }
diff --git a/racket/src/racket/gc2/vm_osk.c b/racket/src/racket/gc2/vm_osk.c
index e05cf81b85..2bf9476d56 100644
--- a/racket/src/racket/gc2/vm_osk.c
+++ b/racket/src/racket/gc2/vm_osk.c
@@ -9,14 +9,14 @@
 
 #include <oskit/c/malloc.h>
 
-inline static void *os_malloc_pages(MMU *mmu, size_t len, size_t alignment, int dirty_ok)
+inline static void *os_alloc_aligned_pages(size_t len, size_t alignment, int dirty_ok)
 {
   void *p;
 
   p = smemalign(alignment, len);
   
   if (!dirty_ok)
-  memset(p, 0, len);
+    memset(p, 0, len);
 
   return p;
 }
diff --git a/racket/src/racket/gc2/vm_win.c b/racket/src/racket/gc2/vm_win.c
index 778f2ffe12..dbef62f0a4 100644
--- a/racket/src/racket/gc2/vm_win.c
+++ b/racket/src/racket/gc2/vm_win.c
@@ -7,91 +7,19 @@
       DONT_NEED_MAX_HEAP_SIZE --- to disable a provide
 */
 
-/* Cache doesn't seem to help in Windows: */
-#define CACHE_SLOTS 0
-
-#if CACHE_SLOTS
-typedef struct {
-  size_t len;
-  void *page;
-} alloc_cache_entry;
-
-/* First dimension is age: */
-static alloc_cache_entry cache[2][CACHE_SLOTS];
-#endif
-
-static void *os_alloc_pages(MMU *mmu, size_t len, size_t alignment, int dirty_ok)
+static void *os_alloc_pages(size_t len)
 {
-#if CACHE_SLOTS
-  {
-    int i, j;
-
-    for (j = 0; j < 2; j++) {
-      for (i = 0; i < CACHE_SLOTS; i++) {
-        if (cache[j][i].len == len) {
-          if (cache[j][i].page) {
-            void *result = cache[j][i].page;
-            cache[j][i].page = *(void **)result;
-            memset(result, 0, len);
-            return result;
-          }
-          break;
-        }
-      }
-    }
-  }
-#endif
-
   /* VirtualAlloc MEM_COMMIT always zeros memory */
   return (void *)VirtualAlloc(NULL, len, 
 			      MEM_COMMIT | MEM_RESERVE, 
 			      PAGE_READWRITE);
 }
 
-static void os_free_pages(MMU *mmu, void *p, size_t len)
+static void os_free_pages(void *p, size_t len)
 {
-
-#if CACHE_SLOTS
-  {
-    int i;
-
-    for (i = 0; i < CACHE_SLOTS; i++) {
-      if (!cache[0][i].len)
-        cache[0][i].len = len;
-      if (cache[0][i].len == len) {
-        *(void **)p = cache[0][i].page;
-        cache[0][i].page = p;
-        return;
-      }
-    }
-  }
-#endif
-
   VirtualFree(p, 0, MEM_RELEASE);
 }
 
-static void os_flush_freed_pages(MMU *mmu)
-{
-#if CACHE_SLOTS
-  int i;
-  void *p, *next;
-
-  for (i = 0; i < CACHE_SLOTS; i++) {
-    if (cache[1][i].len) {
-      for (p = cache[1][i].page; p; p = next) {
-        next = *(void **)p;
-        mmu_memory_allocated_dec(mmu, cache[i].len);
-        VirtualFree(p, 0, MEM_RELEASE);
-      }
-    }
-    cache[1][i].len = cache[0][i].len;
-    cache[1][i].page = cache[0][i].page;
-    cache[0][i].len = 0;
-    cache[0][i].page = NULL;
-  }
-#endif
-}
-
 static void os_protect_pages(void *p, size_t len, int writeable)
 {
   DWORD old;
diff --git a/racket/src/racket/gc2/xform-mod.rkt b/racket/src/racket/gc2/xform-mod.rkt
index 310451f383..1aa2691128 100644
--- a/racket/src/racket/gc2/xform-mod.rkt
+++ b/racket/src/racket/gc2/xform-mod.rkt
@@ -65,7 +65,7 @@
       (call-with-output-file fn
         (lambda (out)
           (fprintf out "#define ~a ~a\n" (cadr m) (caddr m)))
-        'truncate/replace)
+        #:exists 'truncate/replace)
       (set! cpp (string-append cpp (format " -include ~a" fn)))]
      [else
       (set! cpp (string-append cpp " -D"
diff --git a/racket/src/racket/include/mzwin.def b/racket/src/racket/include/mzwin.def
index 793ff308dd..da4a740a0f 100644
--- a/racket/src/racket/include/mzwin.def
+++ b/racket/src/racket/include/mzwin.def
@@ -96,9 +96,6 @@ EXPORTS
  scheme_set_can_break
  scheme_push_break_enable
  scheme_pop_break_enable
- scheme_with_stack_freeze
- scheme_frozen_run_some
- scheme_is_in_frozen_stack
  scheme_abort_continuation_no_dws
  scheme_call_with_composable_no_dws
  scheme_set_on_atomic_timeout
diff --git a/racket/src/racket/include/mzwin3m.def b/racket/src/racket/include/mzwin3m.def
index eec3094382..7f679de91d 100644
--- a/racket/src/racket/include/mzwin3m.def
+++ b/racket/src/racket/include/mzwin3m.def
@@ -96,9 +96,6 @@ EXPORTS
  scheme_set_can_break
  scheme_push_break_enable
  scheme_pop_break_enable
- scheme_with_stack_freeze
- scheme_frozen_run_some
- scheme_is_in_frozen_stack
  scheme_abort_continuation_no_dws
  scheme_call_with_composable_no_dws
  scheme_set_on_atomic_timeout
diff --git a/racket/src/racket/include/racket.exp b/racket/src/racket/include/racket.exp
index 737fc804b0..88d46c806f 100644
--- a/racket/src/racket/include/racket.exp
+++ b/racket/src/racket/include/racket.exp
@@ -93,9 +93,6 @@ scheme_pop_kill_action
 scheme_set_can_break
 scheme_push_break_enable
 scheme_pop_break_enable
-scheme_with_stack_freeze
-scheme_frozen_run_some
-scheme_is_in_frozen_stack
 scheme_abort_continuation_no_dws
 scheme_call_with_composable_no_dws
 scheme_set_on_atomic_timeout
diff --git a/racket/src/racket/include/racket3m.exp b/racket/src/racket/include/racket3m.exp
index 1905f9ad9f..79f600736c 100644
--- a/racket/src/racket/include/racket3m.exp
+++ b/racket/src/racket/include/racket3m.exp
@@ -93,9 +93,6 @@ scheme_pop_kill_action
 scheme_set_can_break
 scheme_push_break_enable
 scheme_pop_break_enable
-scheme_with_stack_freeze
-scheme_frozen_run_some
-scheme_is_in_frozen_stack
 scheme_abort_continuation_no_dws
 scheme_call_with_composable_no_dws
 scheme_set_on_atomic_timeout
diff --git a/racket/src/racket/include/scheme.h b/racket/src/racket/include/scheme.h
index 3bf595de04..6de06b078e 100644
--- a/racket/src/racket/include/scheme.h
+++ b/racket/src/racket/include/scheme.h
@@ -2128,8 +2128,8 @@ extern Scheme_Extension_Table *scheme_extension_table;
 # define MZ_FD_CLR(n, p) scheme_fdclr(p, n)
 # define MZ_FD_ISSET(n, p) scheme_fdisset(p, n)
 #else
-# define MZ_GET_FDSET(p, n) ((void *)(((fd_set *)p) + n))
-# define MZ_FD_ZERO(p) FD_ZERO((fd_set *)(p))
+# define MZ_GET_FDSET(p, n) ((void *)(((fd_set *)p) XFORM_OK_PLUS n))
+# define MZ_FD_ZERO(p) XFORM_HIDE_EXPR(FD_ZERO((fd_set *)(p)))
 # define MZ_FD_SET(n, p) FD_SET(n, (fd_set *)(p))
 # define MZ_FD_CLR(n, p) FD_CLR(n, (fd_set *)(p))
 # define MZ_FD_ISSET(n, p) FD_ISSET(n, (fd_set *)(p))
diff --git a/racket/src/racket/include/schthread.h b/racket/src/racket/include/schthread.h
index 54f1cdc1af..a8df7b7f10 100644
--- a/racket/src/racket/include/schthread.h
+++ b/racket/src/racket/include/schthread.h
@@ -49,7 +49,7 @@ extern "C" {
 #endif
 
 /* Set up MZ_EXTERN for DLL build */
-#if (defined(__WIN32__) || defined(WIN32) || defined(_WIN32)) \
+#if (defined(__WIN32__) || defined(WIN32) || defined(_WIN32) || defined(__CYGWIN32__)) \
     && !defined(LINK_EXTENSIONS_BY_TABLE) \
     && !defined(SCHEME_EMBEDDED_NO_DLL)
 # define MZ_DLLIMPORT __declspec(dllimport)
@@ -59,10 +59,16 @@ extern "C" {
 # else
 #  define MZ_DLLSPEC __declspec(dllimport)
 # endif
+# if (defined(__CYGWIN32__) && !defined(MZ_USES_SHARED_LIB)) || defined(MZ_PRECISE_GC)
+#  define MZGC_DLLIMPORT
+# else
+#  define MZGC_DLLIMPORT MZ_DLLIMPORT
+# endif
 #else
 # define MZ_DLLSPEC
 # define MZ_DLLIMPORT
 # define MZ_DLLEXPORT
+# define MZGC_DLLIMPORT
 #endif
 
 #define MZ_EXTERN extern MZ_DLLSPEC
diff --git a/racket/src/racket/main.c b/racket/src/racket/main.c
index bf75f44f31..9330e204d3 100644
--- a/racket/src/racket/main.c
+++ b/racket/src/racket/main.c
@@ -31,7 +31,9 @@
    (except for the garbage collector, which is in `gc', `sgc', or
    `gc2', depending on which one you're using). */
 
-#define __MINGW32_DELAY_LOAD__ 1
+#ifdef __MINGW32__
+# define __MINGW32_DELAY_LOAD__ 1
+#endif
 #include "scheme.h"
 
 /*========================================================================*/
diff --git a/racket/src/racket/sconfig.h b/racket/src/racket/sconfig.h
index 0aa3fff6bf..fdab893c98 100644
--- a/racket/src/racket/sconfig.h
+++ b/racket/src/racket/sconfig.h
@@ -589,9 +589,6 @@
 
 # define DO_STACK_CHECK
 # define WINDOWS_FIND_STACK_BOUNDS
-/* Default stack size is 1MB, but we try to read
-   the actual size from the executable on startup: */
-# define WINDOWS_DEFAULT_STACK_SIZE 1048576
 
 # if !defined(_WIN64) || (_MSC_VER >= 1600)
 #  define USE_MZ_SETJMP
@@ -731,10 +728,6 @@
 
 # define REGISTER_POOR_MACHINE
 
-# ifndef AS_MSVC_EXTENSION
-#  define LINK_EXTENSIONS_BY_TABLE
-# endif
-
 # define MZ_USE_JIT_I386
 
 # define FLAGS_ALREADY_SET
diff --git a/racket/src/racket/sgc/Makefile.in b/racket/src/racket/sgc/Makefile.in
index dd1e45fad6..969c8229fa 100644
--- a/racket/src/racket/sgc/Makefile.in
+++ b/racket/src/racket/sgc/Makefile.in
@@ -7,6 +7,10 @@ prefix = @prefix@
 exec_prefix = @exec_prefix@
 libdir = @libdir@
 
+# for version.mak:
+mainsrcdir = @srcdir@/../..
+@INCLUDEDEP@ @srcdir@/../version.mak
+
 CC = @CC@
 CXX = @CXX@
 RANLIB = @RANLIB@
@@ -32,7 +36,7 @@ test: $(OBJS) test.@LTO@
 gcobjects: $(OBJS)
 
 sgc.@LTO@: $(srcdir)/sgc.c $(srcdir)/autostat.inc $(srcdir)/collect.inc $(srcdir)/../utils/splay.c
-	$(CC) $(CFLAGS) $(CPPFLAGS) @OPTIONS@ -I.. -c $(srcdir)/sgc.c -o sgc.@LTO@
+	$(CC) $(CFLAGS) $(CPPFLAGS) @OPTIONS@ -DSGC_EXPORTS -I.. -c $(srcdir)/sgc.c -o sgc.@LTO@
 
 test.@LTO@: $(srcdir)/test.c
 	$(CC) $(CFLAGS) $(CPPFLAGS) @OPTIONS@ -c $(srcdir)/test.c -o test.@LTO@
diff --git a/racket/src/racket/sgc/sgc.h b/racket/src/racket/sgc/sgc.h
index 0dae616728..64c65d6a4a 100644
--- a/racket/src/racket/sgc/sgc.h
+++ b/racket/src/racket/sgc/sgc.h
@@ -7,8 +7,8 @@ extern "C" {
 
 #define GC_PTR void*
 
-#ifdef WIN32
-# ifdef SGC_EXPORTS
+#if defined(WIN32) || defined(__CYGWIN32__)
+# if defined(SGC_EXPORTS) || (defined(__CYGWIN32__) && !defined(MZ_USES_SHARED_LIB))
 #  define SGC_EXTERN __declspec(dllexport)
 # else
 #  define SGC_EXTERN __declspec(dllimport)
diff --git a/racket/src/racket/src/eval.c b/racket/src/racket/src/eval.c
index bf698d4783..d7bb626f9d 100644
--- a/racket/src/racket/src/eval.c
+++ b/racket/src/racket/src/eval.c
@@ -543,6 +543,7 @@ static uintptr_t adjust_stack_base(uintptr_t bnd) {
 #ifdef WINDOWS_FIND_STACK_BOUNDS
 intptr_t find_exe_stack_size()
 {
+# define WINDOWS_DEFAULT_STACK_SIZE 1048576
   intptr_t sz = WINDOWS_DEFAULT_STACK_SIZE;
   wchar_t *fn;
   DWORD len = 1024;
@@ -580,7 +581,6 @@ intptr_t find_exe_stack_size()
 		/* Skip to PE32[+] header's stack reservation value: */
 		if (SetFilePointer(fd, pos + 20 + 4 + 72, NULL, FILE_BEGIN)
 		    != INVALID_SET_FILE_POINTER) {
-		  mzlonglong lsz;
 		  if (kind == 0x10b) {
 		    /* PE32: 32-bit stack size: */
 		    int ssz;
diff --git a/racket/src/racket/src/list.c b/racket/src/racket/src/list.c
index 9edce7da65..4018d18b62 100644
--- a/racket/src/racket/src/list.c
+++ b/racket/src/racket/src/list.c
@@ -3494,13 +3494,13 @@ extern void *GC_base(void *d);
 # define GC_did_mark_stack_overflow() 0
 # define GC_mark_overflow_recover(ptr) /**/
 #else
-extern MZ_DLLIMPORT void *GC_base(void *);
-extern MZ_DLLIMPORT int GC_is_marked(void *);
-extern MZ_DLLIMPORT int GC_did_mark_stack_overflow(void);
-extern MZ_DLLIMPORT void GC_mark_overflow_recover(void *p);
+extern MZGC_DLLIMPORT void *GC_base(void *);
+extern MZGC_DLLIMPORT int GC_is_marked(void *);
+extern MZGC_DLLIMPORT int GC_did_mark_stack_overflow(void);
+extern MZGC_DLLIMPORT void GC_mark_overflow_recover(void *p);
 #endif
-extern MZ_DLLIMPORT void GC_push_all_stack(void *, void *);
-extern MZ_DLLIMPORT void GC_flush_mark_stack(void);
+extern MZGC_DLLIMPORT void GC_push_all_stack(void *, void *);
+extern MZGC_DLLIMPORT void GC_flush_mark_stack(void);
 
 #endif
 
@@ -3674,7 +3674,7 @@ void scheme_clear_ephemerons()
   done_ephemerons = NULL;
 }
 
-extern MZ_DLLIMPORT void (*GC_custom_finalize)();
+extern MZGC_DLLIMPORT void (*GC_custom_finalize)();
 
 void scheme_init_ephemerons(void)
 {
diff --git a/racket/src/racket/src/port.c b/racket/src/racket/src/port.c
index 4229ef703e..7f357783f3 100644
--- a/racket/src/racket/src/port.c
+++ b/racket/src/racket/src/port.c
@@ -1212,7 +1212,7 @@ void scheme_fdzero(void *fd)
   scheme_init_fdset_array(fd, 1);
 # else
 #  if defined(FILES_HAVE_FDS) || defined(USE_TCP)
-  FD_ZERO((fd_set *)fd);
+  XFORM_HIDE_EXPR(FD_ZERO((fd_set *)fd));
 #  endif
 # endif
 }
diff --git a/racket/src/racket/src/salloc.c b/racket/src/racket/src/salloc.c
index 8e0fd64d1f..804639ca1d 100644
--- a/racket/src/racket/src/salloc.c
+++ b/racket/src/racket/src/salloc.c
@@ -91,8 +91,8 @@ void **GC_variable_stack;
 #endif
 
 #ifndef MZ_PRECISE_GC
-extern MZ_DLLIMPORT void GC_register_late_disappearing_link(void **link, void *obj);
-extern MZ_DLLIMPORT void GC_register_indirect_disappearing_link(void **link, void *obj);
+extern MZGC_DLLIMPORT void GC_register_late_disappearing_link(void **link, void *obj);
+extern MZGC_DLLIMPORT void GC_register_indirect_disappearing_link(void **link, void *obj);
 #endif
 
 SHARED_OK static int use_registered_statics;
@@ -102,7 +102,7 @@ SHARED_OK static int use_registered_statics;
 /************************************************************************/
 
 #if !defined(MZ_PRECISE_GC) && !defined(USE_SENORA_GC)
-extern MZ_DLLIMPORT void GC_init();
+extern MZGC_DLLIMPORT void GC_init();
 #endif
 
 void scheme_set_stack_base(void *base, int no_auto_statics) XFORM_SKIP_PROC
@@ -1688,7 +1688,7 @@ void scheme_unused_intptr(intptr_t i) { }
 extern "C" 
 {
 # endif
-  extern MZ_DLLIMPORT void GC_dump(void);
+  extern MZGC_DLLIMPORT void GC_dump(void);
 # ifdef __cplusplus
 };
 # endif
diff --git a/racket/src/racket/src/schemef.h b/racket/src/racket/src/schemef.h
index 0a5e3ed026..75a03665ca 100644
--- a/racket/src/racket/src/schemef.h
+++ b/racket/src/racket/src/schemef.h
@@ -201,12 +201,8 @@ MZ_EXTERN void scheme_set_can_break(int on);
 MZ_EXTERN void scheme_push_break_enable(Scheme_Cont_Frame_Data *cframe, int on, int pre_check);
 MZ_EXTERN void scheme_pop_break_enable(Scheme_Cont_Frame_Data *cframe, int post_check);
 
-MZ_EXTERN int scheme_with_stack_freeze(Scheme_Frozen_Stack_Proc wha_f, void *wha_data);
-MZ_EXTERN int scheme_frozen_run_some(Scheme_Frozen_Stack_Proc do_f, void *do_data, int run_msecs);
-MZ_EXTERN int scheme_is_in_frozen_stack();
-
-MZ_EXTERN Scheme_Object *scheme_abort_continuation_no_dws (Scheme_Object *pt, Scheme_Object *v);
-MZ_EXTERN Scheme_Object *scheme_call_with_composable_no_dws (Scheme_Object *proc, Scheme_Object *pt);
+MZ_EXTERN Scheme_Object *scheme_abort_continuation_no_dws(Scheme_Object *pt, Scheme_Object *v);
+MZ_EXTERN Scheme_Object *scheme_call_with_composable_no_dws(Scheme_Object *proc, Scheme_Object *pt);
 
 MZ_EXTERN Scheme_On_Atomic_Timeout_Proc scheme_set_on_atomic_timeout(Scheme_On_Atomic_Timeout_Proc p);
 
@@ -1229,5 +1225,5 @@ MZ_EXTERN void *scheme_register_process_global(const char *key, void *val);
 MZ_EXTERN Scheme_Object *scheme_malloc_key(void);
 MZ_EXTERN void scheme_free_key(Scheme_Object *k);
 
-MZ_EXTERN void* scheme_jit_find_code_end(void *p);
+MZ_EXTERN void *scheme_jit_find_code_end(void *p);
 MZ_EXTERN void scheme_jit_now(Scheme_Object *f);
diff --git a/racket/src/racket/src/schemex.h b/racket/src/racket/src/schemex.h
index e82bd9189a..97dcfd9b4e 100644
--- a/racket/src/racket/src/schemex.h
+++ b/racket/src/racket/src/schemex.h
@@ -145,11 +145,8 @@ void (*scheme_pop_kill_action)();
 void (*scheme_set_can_break)(int on);
 void (*scheme_push_break_enable)(Scheme_Cont_Frame_Data *cframe, int on, int pre_check);
 void (*scheme_pop_break_enable)(Scheme_Cont_Frame_Data *cframe, int post_check);
-int (*scheme_with_stack_freeze)(Scheme_Frozen_Stack_Proc wha_f, void *wha_data);
-int (*scheme_frozen_run_some)(Scheme_Frozen_Stack_Proc do_f, void *do_data, int run_msecs);
-int (*scheme_is_in_frozen_stack)();
-Scheme_Object *scheme_abort_continuation_no_dws;
-Scheme_Object *scheme_call_with_composable_no_dws;
+Scheme_Object *(*scheme_abort_continuation_no_dws)(Scheme_Object *pt, Scheme_Object *v);
+Scheme_Object *(*scheme_call_with_composable_no_dws)(Scheme_Object *proc, Scheme_Object *pt);
 Scheme_On_Atomic_Timeout_Proc (*scheme_set_on_atomic_timeout)(Scheme_On_Atomic_Timeout_Proc p);
 /*========================================================================*/
 /*                              error handling                            */
@@ -1001,7 +998,7 @@ Scheme_Hash_Table *(*scheme_get_place_table)(void);
 void *(*scheme_register_process_global)(const char *key, void *val);
 Scheme_Object *(*scheme_malloc_key)(void);
 void (*scheme_free_key)(Scheme_Object *k);
- (*scheme_jit_find_code_end)(void *p);
+void *(*scheme_jit_find_code_end)(void *p);
 void (*scheme_jit_now)(Scheme_Object *f);
 #ifndef SCHEME_EX_INLINE
 } Scheme_Extension_Table;
diff --git a/racket/src/racket/src/schemex.inc b/racket/src/racket/src/schemex.inc
index 8f4850d639..3ef9946405 100644
--- a/racket/src/racket/src/schemex.inc
+++ b/racket/src/racket/src/schemex.inc
@@ -102,9 +102,6 @@
   scheme_extension_table->scheme_set_can_break = scheme_set_can_break;
   scheme_extension_table->scheme_push_break_enable = scheme_push_break_enable;
   scheme_extension_table->scheme_pop_break_enable = scheme_pop_break_enable;
-  scheme_extension_table->scheme_with_stack_freeze = scheme_with_stack_freeze;
-  scheme_extension_table->scheme_frozen_run_some = scheme_frozen_run_some;
-  scheme_extension_table->scheme_is_in_frozen_stack = scheme_is_in_frozen_stack;
   scheme_extension_table->scheme_abort_continuation_no_dws = scheme_abort_continuation_no_dws;
   scheme_extension_table->scheme_call_with_composable_no_dws = scheme_call_with_composable_no_dws;
   scheme_extension_table->scheme_set_on_atomic_timeout = scheme_set_on_atomic_timeout;
diff --git a/racket/src/racket/src/schemexm.h b/racket/src/racket/src/schemexm.h
index 362c47c556..aaf2ede556 100644
--- a/racket/src/racket/src/schemexm.h
+++ b/racket/src/racket/src/schemexm.h
@@ -102,9 +102,6 @@
 #define scheme_set_can_break (scheme_extension_table->scheme_set_can_break)
 #define scheme_push_break_enable (scheme_extension_table->scheme_push_break_enable)
 #define scheme_pop_break_enable (scheme_extension_table->scheme_pop_break_enable)
-#define scheme_with_stack_freeze (scheme_extension_table->scheme_with_stack_freeze)
-#define scheme_frozen_run_some (scheme_extension_table->scheme_frozen_run_some)
-#define scheme_is_in_frozen_stack (scheme_extension_table->scheme_is_in_frozen_stack)
 #define scheme_abort_continuation_no_dws (scheme_extension_table->scheme_abort_continuation_no_dws)
 #define scheme_call_with_composable_no_dws (scheme_extension_table->scheme_call_with_composable_no_dws)
 #define scheme_set_on_atomic_timeout (scheme_extension_table->scheme_set_on_atomic_timeout)
diff --git a/racket/src/racket/src/setjmpup.c b/racket/src/racket/src/setjmpup.c
index 7f59fe0089..e5e29aa4c6 100644
--- a/racket/src/racket/src/setjmpup.c
+++ b/racket/src/racket/src/setjmpup.c
@@ -47,10 +47,10 @@ HOOK_SHARED_OK void (*scheme_set_external_stack_val)(void *);
    stack copy to account for pointers to the interior of collectable
    objects. */     
 
-extern MZ_DLLIMPORT void GC_push_all_stack(void *, void *);
-extern MZ_DLLIMPORT void GC_flush_mark_stack(void);
-extern MZ_DLLIMPORT void (*GC_push_last_roots)(void);
-extern MZ_DLLIMPORT void (*GC_push_last_roots_again)(void);
+extern MZGC_DLLIMPORT void GC_push_all_stack(void *, void *);
+extern MZGC_DLLIMPORT void GC_flush_mark_stack(void);
+extern MZGC_DLLIMPORT void (*GC_push_last_roots)(void);
+extern MZGC_DLLIMPORT void (*GC_push_last_roots_again)(void);
 /* GC_push_last_roots_again is called after marking eager
    finalizations (once at each stage). We rely on the fact that no
    copied stack will be referenced by (or affected the ordering of)
@@ -60,8 +60,8 @@ extern MZ_DLLIMPORT void (*GC_push_last_roots_again)(void);
 # define GC_is_marked(p) GC_base(p)
 # define GC_did_mark_stack_overflow() 0
 #else
-extern MZ_DLLIMPORT int GC_is_marked(void *);
-extern MZ_DLLIMPORT int GC_did_mark_stack_overflow(void);
+extern MZGC_DLLIMPORT int GC_is_marked(void *);
+extern MZGC_DLLIMPORT int GC_did_mark_stack_overflow(void);
 #endif
 
 #define get_copy(s_c) (((CopiedStack *)s_c)->_stack_copy)
@@ -673,12 +673,13 @@ void scheme_reset_jmpup_buf(Scheme_Jumpup_Buf *b)
    is fragile, because it's not well defined whether the compiler
    will generate frame-pointer setup; use mzsj86g.S, instead. */
 
-#ifdef __MINGW32__
-# if __OPTIMIZE__ > 0
-#  define NEED_STACK_FRAME_SETUP
-# endif
+#if (__OPTIMIZE__ > 0) || defined(MZ_XFORM)
+# define NEED_STACK_FRAME_SETUP
 #endif
 
+MZ_DO_NOT_INLINE(int scheme_mz_setjmp(mz_pre_jmp_buf b));
+MZ_DO_NOT_INLINE(void scheme_mz_longjmp(mz_pre_jmp_buf b, int v));
+
 int scheme_mz_setjmp(mz_pre_jmp_buf b)
 {
 #ifdef NEED_STACK_FRAME_SETUP
diff --git a/racket/src/racket/src/symbol.c b/racket/src/racket/src/symbol.c
index 9068fdd366..d53b927fdd 100644
--- a/racket/src/racket/src/symbol.c
+++ b/racket/src/racket/src/symbol.c
@@ -41,7 +41,7 @@
 #endif
 
 #ifndef MZ_PRECISE_GC
-extern MZ_DLLIMPORT void (*GC_custom_finalize)(void);
+extern MZGC_DLLIMPORT void (*GC_custom_finalize)(void);
 #endif
 #ifndef USE_SENORA_GC
 extern int GC_is_marked(void *);