libguile/frames.h

   1 /* Copyright (C) 2001, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc.
   2  * *
   3  * This library is free software; you can redistribute it and/or
   4  * modify it under the terms of the GNU Lesser General Public License
   5  * as published by the Free Software Foundation; either version 3 of
   6  * the License, or (at your option) any later version.
   7  *
   8  * This library is distributed in the hope that it will be useful, but
   9  * WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * Lesser General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public
  14  * License along with this library; if not, write to the Free Software
  15  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  16  * 02110-1301 USA
  17  */
  18
  19 #ifndef _SCM_FRAMES_H_
  20 #define _SCM_FRAMES_H_
  21
  22 #include <libguile.h>
  23 #include "programs.h"
  24
  25 \f
  26 /*
  27  * VM frames
  28  */
  29
  30 /*
  31  * It's a little confusing, but there are two representations of frames in this
  32  * file: frame pointers and Scheme objects wrapping those frame pointers. The
  33  * former uses the SCM_FRAME_... macro prefix, the latter SCM_VM_FRAME_..
  34  * prefix.
  35  *
  36  * The confusing thing is that only Scheme frame objects have functions that use
  37  * them, and they use the scm_frame_.. prefix. Hysterical raisins.
  38  */
  39
  40 /* VM Frame Layout
  41    ---------------
  42
  43    | ...              |
  44    | Intermed. val. 0 | <- fp + nargs + nlocs
  45    +------------------+
  46    | Local variable 1 |
  47    | Local variable 0 | <- fp + nargs
  48    | Argument 1       |
  49    | Argument 0       | <- fp = SCM_FRAME_STACK_ADDRESS (fp)
  50    | Program          | <- fp - 1
  51    +==================+
  52    | Return address   | <- SCM_FRAME_UPPER_ADDRESS (fp)
  53    | Dynamic link     | <- fp - 3 = SCM_FRAME_DATA_ADDRESS (fp) = SCM_FRAME_LOWER_ADDRESS (fp)
  54    +==================+
  55    |                  |
  56
  57    As can be inferred from this drawing, it is assumed that
  58    `sizeof (SCM *) == sizeof (SCM)', since pointers (the `link' parts) are
  59    assumed to be as long as SCM objects.
  60
  61    When a program returns multiple values, it will shuffle them down to
  62    start contiguously from slot 1, as for a tail call.  This means that
  63    when the caller goes to access them, there are 2 or 3 empty words
  64    between the top of the caller stack and the bottom of the values,
  65    corresponding to the frame that was just popped.
  66 */
  67
  68 /* This structure maps to the contents of a VM stack frame.  It can
  69    alias a frame directly.  */
  70 struct scm_vm_frame
  71 {
  72   SCM *dynamic_link;
  73   scm_t_uint8 *return_address;
  74   SCM program;
  75   SCM stack[1]; /* Variable-length */
  76 };
  77
  78 #define SCM_FRAME_STRUCT(fp)                            \
  79   ((struct scm_vm_frame *) SCM_FRAME_DATA_ADDRESS (fp))
  80
  81 #define SCM_FRAME_DATA_ADDRESS(fp)      (((SCM *) (fp)) - 3)
  82 #define SCM_FRAME_STACK_ADDRESS(fp)     (SCM_FRAME_STRUCT (fp)->stack)
  83 #define SCM_FRAME_UPPER_ADDRESS(fp)     ((SCM*)&SCM_FRAME_STRUCT (fp)->return_address)
  84 #define SCM_FRAME_LOWER_ADDRESS(fp)     ((SCM*)SCM_FRAME_STRUCT (fp))
  85
  86 #define SCM_FRAME_BYTE_CAST(x)          ((scm_t_uint8 *) SCM_UNPACK (x))
  87 #define SCM_FRAME_STACK_CAST(x)         ((SCM *) SCM_UNPACK (x))
  88
  89 #define SCM_FRAME_RETURN_ADDRESS(fp)            \
  90   (SCM_FRAME_STRUCT (fp)->return_address)
  91 #define SCM_FRAME_SET_RETURN_ADDRESS(fp, ra)    \
  92   SCM_FRAME_STRUCT (fp)->return_address = (ra)
  93 #define SCM_FRAME_DYNAMIC_LINK(fp)              \
  94   (SCM_FRAME_STRUCT (fp)->dynamic_link)
  95 #define SCM_FRAME_SET_DYNAMIC_LINK(fp, dl)      \
  96   SCM_FRAME_DYNAMIC_LINK (fp) = (dl)
  97 #define SCM_FRAME_VARIABLE(fp,i)                \
  98   (SCM_FRAME_STRUCT (fp)->stack[i])
  99 #define SCM_FRAME_PROGRAM(fp)                   \
 100   (SCM_FRAME_STRUCT (fp)->program)
 101
 102 \f
 103
 104 /* FIXME: Replace SCM_FRAME_RETURN_ADDRESS with these.  */
 105 #define SCM_FRAME_RTL_RETURN_ADDRESS(fp)                \
 106   ((scm_t_uint32 *) SCM_FRAME_RETURN_ADDRESS (fp))
 107 #define SCM_FRAME_SET_RTL_RETURN_ADDRESS(fp, ip)        \
 108   SCM_FRAME_SET_RETURN_ADDRESS (fp, (scm_t_uint8 *) (ip))
 109
 110 \f
 111 /*
 112  * Heap frames
 113  */
 114
 115 struct scm_frame
 116 {
 117   SCM stack_holder;
 118   SCM *fp;
 119   SCM *sp;
 120   scm_t_uint8 *ip;
 121   scm_t_ptrdiff offset;
 122 };
 123
 124 #define SCM_VM_FRAME_P(x)       (SCM_HAS_TYP7 (x, scm_tc7_frame))
 125 #define SCM_VM_FRAME_DATA(x)    ((struct scm_frame*)SCM_CELL_WORD_1 (x))
 126 #define SCM_VM_FRAME_STACK_HOLDER(f)    SCM_VM_FRAME_DATA(f)->stack_holder
 127 #define SCM_VM_FRAME_FP(f)      SCM_VM_FRAME_DATA(f)->fp
 128 #define SCM_VM_FRAME_SP(f)      SCM_VM_FRAME_DATA(f)->sp
 129 #define SCM_VM_FRAME_IP(f)      SCM_VM_FRAME_DATA(f)->ip
 130 #define SCM_VM_FRAME_OFFSET(f)  SCM_VM_FRAME_DATA(f)->offset
 131 #define SCM_VALIDATE_VM_FRAME(p,x)      SCM_MAKE_VALIDATE (p, x, VM_FRAME_P)
 132
 133 SCM_API SCM scm_c_make_frame (SCM stack_holder, SCM *fp, SCM *sp,
 134                               scm_t_uint8 *ip, scm_t_ptrdiff offset);
 135 SCM_API SCM scm_frame_p (SCM obj);
 136 SCM_API SCM scm_frame_procedure (SCM frame);
 137 SCM_API SCM scm_frame_arguments (SCM frame);
 138 SCM_API SCM scm_frame_source (SCM frame);
 139 SCM_API SCM scm_frame_num_locals (SCM frame);
 140 SCM_API SCM scm_frame_local_ref (SCM frame, SCM index);
 141 SCM_API SCM scm_frame_local_set_x (SCM frame, SCM index, SCM val);
 142 SCM_API SCM scm_frame_address (SCM frame);
 143 SCM_API SCM scm_frame_stack_pointer (SCM frame);
 144 SCM_API SCM scm_frame_instruction_pointer (SCM frame);
 145 SCM_API SCM scm_frame_return_address (SCM frame);
 146 SCM_API SCM scm_frame_dynamic_link (SCM frame);
 147 SCM_API SCM scm_frame_previous (SCM frame);
 148
 149 SCM_INTERNAL void scm_i_frame_print (SCM frame, SCM port,
 150                                      scm_print_state *pstate);
 151 SCM_INTERNAL void scm_init_frames (void);
 152
 153 #endif /* _SCM_FRAMES_H_ */
 154
 155 /*
 156   Local Variables:
 157   c-file-style: "gnu"
 158   End:
 159 */