slight frames.h refactor

* libguile/frames.h: Instead of doing a lot of nasty pointer match and
  casts here, simply define a struct that aliases the contents of a
  stack frame.  There are some naming issues here, that the SCM_FRAME
  macros access the scm_vm_frame structure, but SCM_VM_FRAME macros
  access scm_frame; oh well.

diff --git a/libguile/frames.h b/libguile/frames.h
index 47244c7..ffb577a 100644 (file)
--- a/libguile/frames.h
+++ b/libguile/frames.h
@@ -59,28 +59,43 @@
    `sizeof (SCM *) == sizeof (SCM)', since pointers (the `link' parts) are
    assumed to be as long as SCM objects.  */
 
+/* This structure maps to the contents of a VM stack frame.  It can
+   alias a frame directly.  */
+struct scm_vm_frame
+{
+  SCM *dynamic_link;
+  scm_t_uint8 *mv_return_address;
+  scm_t_uint8 *return_address;
+  SCM program;
+  SCM stack[1]; /* Variable-length */
+};
+
+#define SCM_FRAME_STRUCT(fp)           ((struct scm_vm_frame*)(((SCM*)(fp)) - 4))
+
 #define SCM_FRAME_DATA_ADDRESS(fp)     (fp - 4)
-#define SCM_FRAME_STACK_ADDRESS(fp)    (fp)
-#define SCM_FRAME_UPPER_ADDRESS(fp)    (fp - 2)
-#define SCM_FRAME_LOWER_ADDRESS(fp)    (fp - 4)
+#define SCM_FRAME_STACK_ADDRESS(fp)    (SCM_FRAME_STRUCT (fp)->stack)
+#define SCM_FRAME_UPPER_ADDRESS(fp)    ((SCM*)&SCM_FRAME_STRUCT (fp)->return_address)
+#define SCM_FRAME_LOWER_ADDRESS(fp)    ((SCM*)SCM_FRAME_STRUCT (fp))
 
 #define SCM_FRAME_BYTE_CAST(x)         ((scm_t_uint8 *) SCM_UNPACK (x))
 #define SCM_FRAME_STACK_CAST(x)                ((SCM *) SCM_UNPACK (x))
 
-#define SCM_FRAME_RETURN_ADDRESS(fp)                           \
-  (SCM_FRAME_BYTE_CAST (SCM_FRAME_DATA_ADDRESS (fp)[2]))
-#define SCM_FRAME_SET_RETURN_ADDRESS(fp, ra)                   \
-  ((SCM_FRAME_DATA_ADDRESS (fp)[2])) = SCM_PACK (ra)
-#define SCM_FRAME_MV_RETURN_ADDRESS(fp)                                \
-  (SCM_FRAME_BYTE_CAST (SCM_FRAME_DATA_ADDRESS (fp)[1]))
-#define SCM_FRAME_SET_MV_RETURN_ADDRESS(fp, mvra)              \
-  ((SCM_FRAME_DATA_ADDRESS (fp)[1])) = SCM_PACK (mvra)
-#define SCM_FRAME_DYNAMIC_LINK(fp)                             \
-  (SCM_FRAME_STACK_CAST (SCM_FRAME_DATA_ADDRESS (fp)[0]))
-#define SCM_FRAME_SET_DYNAMIC_LINK(fp, dl)                     \
-  ((SCM_FRAME_DATA_ADDRESS (fp)[0])) = SCM_PACK (dl)
-#define SCM_FRAME_VARIABLE(fp,i)       SCM_FRAME_STACK_ADDRESS (fp)[i]
-#define SCM_FRAME_PROGRAM(fp)          SCM_FRAME_STACK_ADDRESS (fp)[-1]
+#define SCM_FRAME_RETURN_ADDRESS(fp)            \
+  (SCM_FRAME_STRUCT (fp)->return_address)
+#define SCM_FRAME_SET_RETURN_ADDRESS(fp, ra)    \
+  SCM_FRAME_STRUCT (fp)->return_address = (ra)
+#define SCM_FRAME_MV_RETURN_ADDRESS(fp)         \
+  (SCM_FRAME_STRUCT (fp)->mv_return_address)
+#define SCM_FRAME_SET_MV_RETURN_ADDRESS(fp, mvra)       \
+  SCM_FRAME_STRUCT (fp)->mv_return_address = (mvra)
+#define SCM_FRAME_DYNAMIC_LINK(fp)              \
+  (SCM_FRAME_STRUCT (fp)->dynamic_link)
+#define SCM_FRAME_SET_DYNAMIC_LINK(fp, dl)      \
+  SCM_FRAME_STRUCT (fp)->dynamic_link = (dl)
+#define SCM_FRAME_VARIABLE(fp,i)                \
+  (SCM_FRAME_STRUCT (fp)->stack[i])
+#define SCM_FRAME_PROGRAM(fp)                   \
+  (SCM_FRAME_STRUCT (fp)->program)
 
 \f
 /*