libguile/control.c

   1 /* Copyright (C) 2010  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 #if HAVE_CONFIG_H
  20 #  include <config.h>
  21 #endif
  22
  23 #include "libguile/_scm.h"
  24 #include "libguile/control.h"
  25 #include "libguile/objcodes.h"
  26 #include "libguile/instructions.h"
  27 #include "libguile/vm.h"
  28
  29 \f
  30
  31 SCM scm_sys_default_prompt_tag;
  32
  33
  34 SCM
  35 scm_c_make_prompt (SCM vm, SCM k, scm_t_uint8 escape_only_p,
  36                    scm_t_int64 vm_cookie)
  37 {
  38   scm_t_bits tag;
  39   SCM ret;
  40   struct scm_prompt_registers *regs;
  41
  42   tag = scm_tc7_prompt;
  43   if (escape_only_p)
  44     tag |= (SCM_F_PROMPT_ESCAPE<<8);
  45   ret = scm_words (tag, 5);
  46
  47   regs = scm_gc_malloc_pointerless (sizeof (*regs), "prompt registers");
  48   regs->fp = SCM_VM_DATA (vm)->fp;
  49   regs->sp = SCM_VM_DATA (vm)->sp;
  50   regs->ip = SCM_VM_DATA (vm)->ip;
  51   regs->cookie = vm_cookie;
  52
  53   SCM_SET_CELL_OBJECT (ret, 1, k);
  54   SCM_SET_CELL_WORD (ret, 2, (scm_t_bits)regs);
  55   SCM_SET_CELL_OBJECT (ret, 3, scm_i_dynwinds ());
  56
  57   return ret;
  58 }
  59
  60 #ifdef WORDS_BIGENDIAN
  61 #define OBJCODE_HEADER(main,meta) 0, 0, 0, main, 0, 0, 0, meta+8
  62 #define META_HEADER(meta)         0, 0, 0, meta, 0, 0, 0, 0
  63 #else
  64 #define OBJCODE_HEADER(main,meta) main, 0, 0, 0, meta+8, 0, 0, 0
  65 #define META_HEADER(meta)         meta, 0, 0, 0, 0,      0, 0, 0
  66 #endif
  67
  68 #define ROUND_UP(len,align) (((len-1)|(align-1))+1)
  69 #define ALIGN_PTR(type,p,align) (type*)(ROUND_UP (((scm_t_bits)p), align))
  70
  71 #ifdef SCM_ALIGNED
  72 #define SCM_DECLARE_STATIC_ALIGNED_ARRAY(type, sym)\
  73 static const type sym[]
  74 #define SCM_STATIC_ALIGNED_ARRAY(alignment, type, sym)\
  75 static SCM_ALIGNED (alignment) const type sym[]
  76 #else
  77 #define SCM_DECLARE_STATIC_ALIGNED_ARRAY(type, sym)\
  78 static type *sym
  79 #define SCM_STATIC_ALIGNED_ARRAY(alignment, type, sym)                  \
  80 SCM_SNARF_INIT(sym = scm_malloc (sizeof(sym##__unaligned) + alignment - 1); \
  81                sym = ALIGN_PTR (type, sym, alignment);                  \
  82                memcpy (sym, sym##__unaligned, sizeof(sym##__unaligned));) \
  83 static type *sym = NULL;                                                \
  84 static const type sym##__unaligned[]
  85 #endif
  86
  87 #define STATIC_OBJCODE_TAG                                      \
  88   SCM_PACK (scm_tc7_objcode | (SCM_F_OBJCODE_IS_STATIC << 8))
  89
  90 #define SCM_STATIC_OBJCODE(sym)                                         \
  91   SCM_DECLARE_STATIC_ALIGNED_ARRAY (scm_t_uint8, sym##__bytecode);      \
  92   SCM_STATIC_ALIGNED_ARRAY (8, scm_t_cell, sym##__cells) = {            \
  93     { STATIC_OBJCODE_TAG, SCM_PACK (sym##__bytecode) },                 \
  94     { SCM_BOOL_F, SCM_PACK (0) }                                        \
  95   };                                                                    \
  96   static const SCM sym = SCM_PACK (sym##__cells);                       \
  97   SCM_STATIC_ALIGNED_ARRAY (8, scm_t_uint8, sym##__bytecode)
  98
  99
 100 SCM_STATIC_OBJCODE (cont_objcode) = {
 101   /* Like in continuations.c, but with partial-cont-call. */
 102   OBJCODE_HEADER (8, 19),
 103   /* leave args on the stack */
 104   /* 0 */ scm_op_object_ref, 0, /* push scm_vm_cont object */
 105   /* 2 */ scm_op_object_ref, 1, /* push internal winds */
 106   /* 4 */ scm_op_partial_cont_call, /* and go! */
 107   /* 5 */ scm_op_nop, scm_op_nop, scm_op_nop, /* pad to 8 bytes */
 108   /* 8 */
 109
 110   /* We could put some meta-info to say that this proc is a continuation. Not sure
 111      how to do that, though. */
 112   META_HEADER (19),
 113   /* 0 */ scm_op_make_eol, /* bindings */
 114   /* 1 */ scm_op_make_eol, /* sources */
 115   /* 2 */ scm_op_make_int8, 0, scm_op_make_int8, 5, /* arity: from ip 0 to ip 7 */
 116   /* 6 */ scm_op_make_int8_0, /* the arity is 0 required args */
 117   /* 7 */ scm_op_make_int8_0, /* 0 optionals */
 118   /* 8 */ scm_op_make_true, /* and a rest arg */
 119   /* 9 */ scm_op_list, 0, 5, /* make a list of those 5 vals */
 120   /* 12 */ scm_op_list, 0, 1, /* and the arities will be a list of that one list */
 121   /* 15 */ scm_op_list, 0, 3, /* pack bindings, sources, and arities into list */
 122   /* 18 */ scm_op_return /* and return */
 123   /* 19 */
 124 };
 125
 126
 127 static SCM
 128 reify_partial_continuation (SCM vm, SCM prompt, SCM extwinds,
 129                             scm_t_int64 cookie)
 130 {
 131   SCM vm_cont, dynwinds, intwinds = SCM_EOL, ret;
 132   scm_t_uint32 flags;
 133
 134   /* No need to reify if the continuation is never referenced in the handler. */
 135   if (SCM_PROMPT_ESCAPE_P (prompt))
 136     return SCM_BOOL_F;
 137
 138   dynwinds = scm_i_dynwinds ();
 139   while (!scm_is_eq (dynwinds, extwinds))
 140     {
 141       intwinds = scm_cons (scm_car (dynwinds), intwinds);
 142       dynwinds = scm_cdr (dynwinds);
 143     }
 144
 145   flags = SCM_F_VM_CONT_PARTIAL;
 146   if (cookie >= 0 && SCM_PROMPT_REGISTERS (prompt)->cookie == cookie)
 147     flags |= SCM_F_VM_CONT_REWINDABLE;
 148
 149   /* Since non-escape continuations should begin with a thunk application, the
 150      first bit of the stack should be a frame, with the saved fp equal to the fp
 151      that was current when the prompt was made. */
 152   if ((SCM*)(SCM_PROMPT_REGISTERS (prompt)->sp[1])
 153       != SCM_PROMPT_REGISTERS (prompt)->fp)
 154     abort ();
 155
 156   /* Capture from the top of the thunk application frame up to the end. Set an
 157      MVRA only, as the post-abort code is in an MV context. */
 158   vm_cont = scm_i_vm_capture_stack (SCM_PROMPT_REGISTERS (prompt)->sp + 4,
 159                                     SCM_VM_DATA (vm)->fp,
 160                                     SCM_VM_DATA (vm)->sp,
 161                                     NULL,
 162                                     SCM_VM_DATA (vm)->ip,
 163                                     flags);
 164
 165   ret = scm_make_program (cont_objcode,
 166                           scm_vector (scm_list_2 (vm_cont, intwinds)),
 167                           SCM_BOOL_F);
 168   SCM_SET_CELL_WORD_0 (ret,
 169                        SCM_CELL_WORD_0 (ret) | SCM_F_PROGRAM_IS_CONTINUATION);
 170   return ret;
 171 }
 172
 173 SCM
 174 scm_c_abort (SCM vm, SCM tag, size_t n, SCM *argv, scm_t_int64 cookie)
 175 {
 176   SCM cont, winds, prompt = SCM_BOOL_F;
 177   long delta;
 178   size_t i;
 179
 180   /* Search the wind list for an appropriate prompt.
 181      "Waiter, please bring us the wind list." */
 182   for (winds = scm_i_dynwinds (), delta = 0;
 183        scm_is_pair (winds);
 184        winds = SCM_CDR (winds), delta++)
 185     {
 186       SCM elt = SCM_CAR (winds);
 187       if (SCM_PROMPT_P (elt) && scm_is_eq (SCM_PROMPT_TAG (elt), tag))
 188         {
 189           prompt = elt;
 190           break;
 191         }
 192     }
 193
 194   /* If we didn't find anything, print a message and abort the process
 195      right here.  If you don't want this, establish a catch-all around
 196      any code that might throw up. */
 197   if (scm_is_false (prompt))
 198     {
 199       if (scm_is_eq (tag, scm_fluid_ref (scm_sys_default_prompt_tag)))
 200         {
 201           fprintf (stderr, "No prompt found for abort to default prompt tag!\n");
 202           abort ();
 203         }
 204       else
 205         scm_misc_error ("abort", "abort to unknown tag", scm_list_1 (tag));
 206     }
 207
 208   cont = reify_partial_continuation (vm, prompt, winds, cookie);
 209
 210   /* Unwind once more, beyond the prompt. */
 211   winds = SCM_CDR (winds), delta++;
 212
 213   /* Unwind */
 214   scm_dowinds (winds, delta);
 215
 216   /* Restore VM regs */
 217   SCM_VM_DATA (vm)->fp = SCM_PROMPT_REGISTERS (prompt)->fp;
 218   SCM_VM_DATA (vm)->sp = SCM_PROMPT_REGISTERS (prompt)->sp;
 219   SCM_VM_DATA (vm)->ip = SCM_PROMPT_REGISTERS (prompt)->ip;
 220
 221   /* Since we're jumping down, we should always have enough space */
 222   if (SCM_VM_DATA (vm)->sp + n + 1 >= SCM_VM_DATA (vm)->stack_limit)
 223     abort ();
 224
 225   /* Push vals */
 226   *(++(SCM_VM_DATA (vm)->sp)) = cont;
 227   for (i = 0; i < n; i++)
 228     *(++(SCM_VM_DATA (vm)->sp)) = argv[i];
 229   *(++(SCM_VM_DATA (vm)->sp)) = scm_from_size_t (n+1); /* +1 for continuation */
 230
 231   /* Jump! */
 232   SCM_I_LONGJMP (SCM_PROMPT_REGISTERS (prompt)->regs, 1);
 233
 234   /* Shouldn't get here */
 235   abort ();
 236 }
 237
 238 SCM_DEFINE (scm_at_abort, "@abort", 2, 0, 0, (SCM tag, SCM args),
 239             "Abort to the nearest prompt with tag @var{tag}.")
 240 #define FUNC_NAME s_scm_at_abort
 241 {
 242   SCM *argv;
 243   size_t i, n;
 244
 245   SCM_VALIDATE_LIST_COPYLEN (SCM_ARG2, args, n);
 246   argv = alloca (sizeof (SCM)*n);
 247   for (i = 0; i < n; i++, args = scm_cdr (args))
 248     argv[i] = scm_car (args);
 249
 250   scm_c_abort (scm_the_vm (), tag, n, argv, -1);
 251
 252   /* Oh, what, you're still here? The abort must have been reinstated. Actually,
 253      that's quite impossible, given that we're already in C-land here, so...
 254      abort! */
 255
 256   abort ();
 257 }
 258 #undef FUNC_NAME
 259
 260 void
 261 scm_init_control (void)
 262 {
 263 #include "control.x"
 264   scm_sys_default_prompt_tag = scm_make_fluid ();
 265   scm_fluid_set_x (scm_sys_default_prompt_tag, scm_gensym (SCM_UNDEFINED));
 266   scm_c_define ("%default-prompt-tag", scm_sys_default_prompt_tag);
 267 }
 268
 269 /*
 270   Local Variables:
 271   c-file-style: "gnu"
 272   End:
 273 */