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
  32 SCM
  33 scm_c_make_prompt (SCM k, SCM *fp, SCM *sp, scm_t_uint8 *abort_ip,
  34                    scm_t_uint8 escape_only_p, scm_t_int64 vm_cookie,
  35                    SCM winds)
  36 {
  37   scm_t_bits tag;
  38   struct scm_prompt_registers *regs;
  39
  40   tag = scm_tc7_prompt;
  41   if (escape_only_p)
  42     tag |= (SCM_F_PROMPT_ESCAPE<<8);
  43
  44   regs = scm_gc_malloc_pointerless (sizeof (*regs), "prompt registers");
  45   regs->fp = fp;
  46   regs->sp = sp;
  47   regs->ip = abort_ip;
  48   regs->cookie = vm_cookie;
  49
  50   return scm_double_cell (tag, SCM_UNPACK (k), (scm_t_bits)regs,
  51                           SCM_UNPACK (winds));
  52 }
  53
  54 /* Only to be called if the SCM_PROMPT_SETJMP returns 1 */
  55 SCM
  56 scm_i_prompt_pop_abort_args_x (SCM prompt)
  57 {
  58   size_t i, n;
  59   SCM vals = SCM_EOL;
  60
  61   n = scm_to_size_t (SCM_PROMPT_REGISTERS (prompt)->sp[0]);
  62   for (i = 0; i < n; i++)
  63     vals = scm_cons (SCM_PROMPT_REGISTERS (prompt)->sp[-(i + 1)], vals);
  64
  65   /* The abort did reset the VM's registers, but then these values
  66      were pushed on; so we need to pop them ourselves. */
  67   SCM_VM_DATA (scm_the_vm ())->sp -= n + 1;
  68   /* FIXME NULLSTACK */
  69
  70   return vals;
  71 }
  72
  73
  74 #ifdef WORDS_BIGENDIAN
  75 #define OBJCODE_HEADER(main,meta) 0, 0, 0, main, 0, 0, 0, meta+8
  76 #define META_HEADER(meta)         0, 0, 0, meta, 0, 0, 0, 0
  77 #else
  78 #define OBJCODE_HEADER(main,meta) main, 0, 0, 0, meta+8, 0, 0, 0
  79 #define META_HEADER(meta)         meta, 0, 0, 0, 0,      0, 0, 0
  80 #endif
  81
  82 #define ALIGN_PTR(type,p,align) (type*)(ROUND_UP (((scm_t_bits)p), align))
  83
  84 #ifdef SCM_ALIGNED
  85 #define SCM_DECLARE_STATIC_ALIGNED_ARRAY(type, sym)     \
  86 static const type sym[]
  87 #define SCM_STATIC_ALIGNED_ARRAY(alignment, type, sym)  \
  88 static SCM_ALIGNED (alignment) const type sym[]
  89 #else
  90 #define SCM_DECLARE_STATIC_ALIGNED_ARRAY(type, sym)     \
  91 static type *sym
  92 #define SCM_STATIC_ALIGNED_ARRAY(alignment, type, sym)                  \
  93 SCM_SNARF_INIT(sym = scm_malloc_pointerless (sizeof(sym##__unaligned); \
  94                memcpy (sym, sym##__unaligned, sizeof(sym##__unaligned));) \
  95 static type *sym = NULL;                                                \
  96 static const type sym##__unaligned[]
  97 #endif
  98
  99 #define STATIC_OBJCODE_TAG                                      \
 100   SCM_PACK (scm_tc7_objcode | (SCM_F_OBJCODE_IS_STATIC << 8))
 101
 102 #define SCM_STATIC_OBJCODE(sym)                                         \
 103   SCM_DECLARE_STATIC_ALIGNED_ARRAY (scm_t_uint8, sym##__bytecode);      \
 104   SCM_STATIC_ALIGNED_ARRAY (8, scm_t_cell, sym##__cells) = {            \
 105     { STATIC_OBJCODE_TAG, SCM_PACK (sym##__bytecode) },                 \
 106     { SCM_BOOL_F, SCM_PACK (0) }                                        \
 107   };                                                                    \
 108   static const SCM sym = SCM_PACK (sym##__cells);                       \
 109   SCM_STATIC_ALIGNED_ARRAY (8, scm_t_uint8, sym##__bytecode)
 110
 111
 112 SCM_STATIC_OBJCODE (cont_objcode) = {
 113   /* Like in continuations.c, but with partial-cont-call. */
 114   OBJCODE_HEADER (8, 19),
 115   /* leave args on the stack */
 116   /* 0 */ scm_op_object_ref, 0, /* push scm_vm_cont object */
 117   /* 2 */ scm_op_object_ref, 1, /* push internal winds */
 118   /* 4 */ scm_op_partial_cont_call, /* and go! */
 119   /* 5 */ scm_op_nop, scm_op_nop, scm_op_nop, /* pad to 8 bytes */
 120   /* 8 */
 121
 122   /* We could put some meta-info to say that this proc is a continuation. Not sure
 123      how to do that, though. */
 124   META_HEADER (19),
 125   /* 0 */ scm_op_make_eol, /* bindings */
 126   /* 1 */ scm_op_make_eol, /* sources */
 127   /* 2 */ scm_op_make_int8, 0, scm_op_make_int8, 5, /* arity: from ip 0 to ip 7 */
 128   /* 6 */ scm_op_make_int8_0, /* the arity is 0 required args */
 129   /* 7 */ scm_op_make_int8_0, /* 0 optionals */
 130   /* 8 */ scm_op_make_true, /* and a rest arg */
 131   /* 9 */ scm_op_list, 0, 5, /* make a list of those 5 vals */
 132   /* 12 */ scm_op_list, 0, 1, /* and the arities will be a list of that one list */
 133   /* 15 */ scm_op_list, 0, 3, /* pack bindings, sources, and arities into list */
 134   /* 18 */ scm_op_return /* and return */
 135   /* 19 */
 136 };
 137
 138
 139 static SCM
 140 reify_partial_continuation (SCM vm, SCM prompt, SCM extwinds,
 141                             scm_t_int64 cookie)
 142 {
 143   SCM vm_cont, dynwinds, intwinds = SCM_EOL, ret;
 144   scm_t_uint32 flags;
 145
 146   /* No need to reify if the continuation is never referenced in the handler. */
 147   if (SCM_PROMPT_ESCAPE_P (prompt))
 148     return SCM_BOOL_F;
 149
 150   dynwinds = scm_i_dynwinds ();
 151   while (!scm_is_eq (dynwinds, extwinds))
 152     {
 153       intwinds = scm_cons (scm_car (dynwinds), intwinds);
 154       dynwinds = scm_cdr (dynwinds);
 155     }
 156
 157   flags = SCM_F_VM_CONT_PARTIAL;
 158   if (cookie >= 0 && SCM_PROMPT_REGISTERS (prompt)->cookie == cookie)
 159     flags |= SCM_F_VM_CONT_REWINDABLE;
 160
 161   /* Since non-escape continuations should begin with a thunk application, the
 162      first bit of the stack should be a frame, with the saved fp equal to the fp
 163      that was current when the prompt was made. */
 164   if ((SCM*)(SCM_PROMPT_REGISTERS (prompt)->sp[1])
 165       != SCM_PROMPT_REGISTERS (prompt)->fp)
 166     abort ();
 167
 168   /* Capture from the top of the thunk application frame up to the end. Set an
 169      MVRA only, as the post-abort code is in an MV context. */
 170   vm_cont = scm_i_vm_capture_stack (SCM_PROMPT_REGISTERS (prompt)->sp + 4,
 171                                     SCM_VM_DATA (vm)->fp,
 172                                     SCM_VM_DATA (vm)->sp,
 173                                     NULL,
 174                                     SCM_VM_DATA (vm)->ip,
 175                                     flags);
 176
 177   ret = scm_make_program (cont_objcode,
 178                           scm_vector (scm_list_2 (vm_cont, intwinds)),
 179                           SCM_BOOL_F);
 180   SCM_SET_CELL_WORD_0 (ret,
 181                        SCM_CELL_WORD_0 (ret) | SCM_F_PROGRAM_IS_PARTIAL_CONTINUATION);
 182   return ret;
 183 }
 184
 185 void
 186 scm_c_abort (SCM vm, SCM tag, size_t n, SCM *argv, scm_t_int64 cookie)
 187 {
 188   SCM cont, winds, prompt = SCM_BOOL_F;
 189   long delta;
 190   size_t i;
 191
 192   /* Search the wind list for an appropriate prompt.
 193      "Waiter, please bring us the wind list." */
 194   for (winds = scm_i_dynwinds (), delta = 0;
 195        scm_is_pair (winds);
 196        winds = SCM_CDR (winds), delta++)
 197     {
 198       SCM elt = SCM_CAR (winds);
 199       if (SCM_PROMPT_P (elt) && scm_is_eq (SCM_PROMPT_TAG (elt), tag))
 200         {
 201           prompt = elt;
 202           break;
 203         }
 204     }
 205
 206   /* If we didn't find anything, raise an error. */
 207   if (scm_is_false (prompt))
 208     scm_misc_error ("abort", "Abort to unknown prompt", scm_list_1 (tag));
 209
 210   cont = reify_partial_continuation (vm, prompt, winds, cookie);
 211
 212   /* Unwind once more, beyond the prompt. */
 213   winds = SCM_CDR (winds), delta++;
 214
 215   /* Unwind */
 216   scm_dowinds (winds, delta);
 217
 218   /* Unwinding may have changed the current thread's VM, so use the
 219      new one.  */
 220   vm = scm_the_vm ();
 221
 222   /* Restore VM regs */
 223   SCM_VM_DATA (vm)->fp = SCM_PROMPT_REGISTERS (prompt)->fp;
 224   SCM_VM_DATA (vm)->sp = SCM_PROMPT_REGISTERS (prompt)->sp;
 225   SCM_VM_DATA (vm)->ip = SCM_PROMPT_REGISTERS (prompt)->ip;
 226
 227   /* Since we're jumping down, we should always have enough space */
 228   if (SCM_VM_DATA (vm)->sp + n + 1 >= SCM_VM_DATA (vm)->stack_limit)
 229     abort ();
 230
 231   /* Push vals */
 232   *(++(SCM_VM_DATA (vm)->sp)) = cont;
 233   for (i = 0; i < n; i++)
 234     *(++(SCM_VM_DATA (vm)->sp)) = argv[i];
 235   *(++(SCM_VM_DATA (vm)->sp)) = scm_from_size_t (n+1); /* +1 for continuation */
 236
 237   /* Jump! */
 238   SCM_I_LONGJMP (SCM_PROMPT_REGISTERS (prompt)->regs, 1);
 239
 240   /* Shouldn't get here */
 241   abort ();
 242 }
 243
 244 SCM_DEFINE (scm_at_abort, "@abort", 2, 0, 0, (SCM tag, SCM args),
 245             "Abort to the nearest prompt with tag @var{tag}.")
 246 #define FUNC_NAME s_scm_at_abort
 247 {
 248   SCM *argv;
 249   size_t i, n;
 250
 251   SCM_VALIDATE_LIST_COPYLEN (SCM_ARG2, args, n);
 252   argv = alloca (sizeof (SCM)*n);
 253   for (i = 0; i < n; i++, args = scm_cdr (args))
 254     argv[i] = scm_car (args);
 255
 256   scm_c_abort (scm_the_vm (), tag, n, argv, -1);
 257
 258   /* Oh, what, you're still here? The abort must have been reinstated. Actually,
 259      that's quite impossible, given that we're already in C-land here, so...
 260      abort! */
 261
 262   abort ();
 263 }
 264 #undef FUNC_NAME
 265
 266 void
 267 scm_i_prompt_print (SCM exp, SCM port, scm_print_state *pstate SCM_UNUSED)
 268 {
 269   scm_puts ("#<prompt ", port);
 270   scm_intprint (SCM_UNPACK (exp), 16, port);
 271   scm_putc ('>', port);
 272 }
 273
 274 void
 275 scm_init_control (void)
 276 {
 277 #include "libguile/control.x"
 278 }
 279
 280 /*
 281   Local Variables:
 282   c-file-style: "gnu"
 283   End:
 284 */