libguile/control.c

   1 /* Copyright (C) 2010, 2011, 2012  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 <alloca.h>
  24
  25 #include "libguile/_scm.h"
  26 #include "libguile/control.h"
  27 #include "libguile/objcodes.h"
  28 #include "libguile/instructions.h"
  29 #include "libguile/vm.h"
  30
  31 \f
  32
  33
  34 SCM
  35 scm_c_make_prompt (SCM k, SCM *fp, SCM *sp, scm_t_uint8 *abort_ip,
  36                    scm_t_uint8 escape_only_p, scm_t_int64 vm_cookie,
  37                    SCM winds)
  38 {
  39   scm_t_bits tag;
  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
  46   regs = scm_gc_malloc_pointerless (sizeof (*regs), "prompt registers");
  47   regs->fp = fp;
  48   regs->sp = sp;
  49   regs->ip = abort_ip;
  50   regs->cookie = vm_cookie;
  51
  52   return scm_double_cell (tag, SCM_UNPACK (k), (scm_t_bits)regs,
  53                           SCM_UNPACK (winds));
  54 }
  55
  56 /* Only to be called if the SCM_PROMPT_SETJMP returns 1 */
  57 SCM
  58 scm_i_prompt_pop_abort_args_x (SCM vm)
  59 {
  60   size_t i, n;
  61   SCM vals = SCM_EOL;
  62
  63   n = scm_to_size_t (SCM_VM_DATA (vm)->sp[0]);
  64   for (i = 0; i < n; i++)
  65     vals = scm_cons (SCM_VM_DATA (vm)->sp[-(i + 1)], vals);
  66
  67   /* The abort did reset the VM's registers, but then these values
  68      were pushed on; so we need to pop them ourselves. */
  69   SCM_VM_DATA (vm)->sp -= n + 1;
  70   /* FIXME NULLSTACK */
  71
  72   return vals;
  73 }
  74
  75
  76 #ifdef WORDS_BIGENDIAN
  77 #define OBJCODE_HEADER(main,meta) 0, 0, 0, main, 0, 0, 0, meta+8
  78 #define META_HEADER(meta)         0, 0, 0, meta, 0, 0, 0, 0
  79 #else
  80 #define OBJCODE_HEADER(main,meta) main, 0, 0, 0, meta+8, 0, 0, 0
  81 #define META_HEADER(meta)         meta, 0, 0, 0, 0,      0, 0, 0
  82 #endif
  83
  84 #define OBJCODE_TAG SCM_MAKE_OBJCODE_TAG (SCM_OBJCODE_TYPE_STATIC, 0)
  85
  86 #if defined (SCM_ALIGNED)
  87 #define SCM_DECLARE_STATIC_ALIGNED_ARRAY(type, sym)     \
  88 static const type sym[]
  89 #define SCM_STATIC_ALIGNED_ARRAY(alignment, type, sym)  \
  90 static SCM_ALIGNED (alignment) const type sym[]
  91 #define SCM_STATIC_OBJCODE(sym)                                         \
  92   SCM_DECLARE_STATIC_ALIGNED_ARRAY (scm_t_uint8, sym##__bytecode);      \
  93   SCM_STATIC_ALIGNED_ARRAY (8, scm_t_cell, sym##__cells) = {            \
  94     { SCM_PACK (OBJCODE_TAG), SCM_PACK (sym##__bytecode) },             \
  95     { SCM_BOOL_F, SCM_PACK (0) }                                        \
  96   };                                                                    \
  97   static const SCM sym = SCM_PACK (sym##__cells);                       \
  98   SCM_STATIC_ALIGNED_ARRAY (8, scm_t_uint8, sym##__bytecode)
  99 #else
 100 #define SCM_STATIC_OBJCODE(sym)                                         \
 101 static SCM sym;                                                         \
 102 static scm_t_uint8 *sym##_bytecode;                                     \
 103 SCM_SNARF_INIT(sym##_bytecode = scm_gc_malloc_pointerless (sizeof(sym##_bytecode__unaligned), "partial continuation stub"); \
 104                memcpy (sym##_bytecode, sym##_bytecode__unaligned, sizeof(sym##_bytecode__unaligned));) \
 105 SCM_SNARF_INIT(sym = scm_double_cell (OBJCODE_TAG,                      \
 106                                       (scm_t_bits)sym##_bytecode,       \
 107                                       SCM_UNPACK (SCM_BOOL_F),          \
 108                                       0);)                              \
 109 static const scm_t_uint8 sym##_bytecode__unaligned[]
 110 #endif
 111
 112
 113 SCM_STATIC_OBJCODE (cont_objcode) = {
 114   /* Like in continuations.c, but with partial-cont-call. */
 115   OBJCODE_HEADER (8, 19),
 116   /* leave args on the stack */
 117   /* 0 */ scm_op_object_ref, 0, /* push scm_vm_cont object */
 118   /* 2 */ scm_op_object_ref, 1, /* push internal winds */
 119   /* 4 */ scm_op_partial_cont_call, /* and go! */
 120   /* 5 */ scm_op_nop, scm_op_nop, scm_op_nop, /* pad to 8 bytes */
 121   /* 8 */
 122
 123   /* We could put some meta-info to say that this proc is a continuation. Not sure
 124      how to do that, though. */
 125   META_HEADER (19),
 126   /* 0 */ scm_op_make_eol, /* bindings */
 127   /* 1 */ scm_op_make_eol, /* sources */
 128   /* 2 */ scm_op_make_int8, 0, scm_op_make_int8, 5, /* arity: from ip 0 to ip 7 */
 129   /* 6 */ scm_op_make_int8_0, /* the arity is 0 required args */
 130   /* 7 */ scm_op_make_int8_0, /* 0 optionals */
 131   /* 8 */ scm_op_make_true, /* and a rest arg */
 132   /* 9 */ scm_op_list, 0, 5, /* make a list of those 5 vals */
 133   /* 12 */ scm_op_list, 0, 1, /* and the arities will be a list of that one list */
 134   /* 15 */ scm_op_list, 0, 3, /* pack bindings, sources, and arities into list */
 135   /* 18 */ scm_op_return /* and return */
 136   /* 19 */
 137 };
 138
 139
 140 static SCM
 141 reify_partial_continuation (SCM vm, SCM prompt, SCM extwinds,
 142                             scm_t_int64 cookie)
 143 {
 144   SCM vm_cont, dynwinds, intwinds = SCM_EOL, ret;
 145   scm_t_uint32 flags;
 146
 147   /* No need to reify if the continuation is never referenced in the handler. */
 148   if (SCM_PROMPT_ESCAPE_P (prompt))
 149     return SCM_BOOL_F;
 150
 151   dynwinds = scm_i_dynwinds ();
 152   while (!scm_is_eq (dynwinds, extwinds))
 153     {
 154       intwinds = scm_cons (scm_car (dynwinds), intwinds);
 155       dynwinds = scm_cdr (dynwinds);
 156     }
 157
 158   flags = SCM_F_VM_CONT_PARTIAL;
 159   if (cookie >= 0 && SCM_PROMPT_REGISTERS (prompt)->cookie == cookie)
 160     flags |= SCM_F_VM_CONT_REWINDABLE;
 161
 162   /* Since non-escape continuations should begin with a thunk application, the
 163      first bit of the stack should be a frame, with the saved fp equal to the fp
 164      that was current when the prompt was made. */
 165   if ((SCM*)SCM_UNPACK (SCM_PROMPT_REGISTERS (prompt)->sp[1])
 166       != SCM_PROMPT_REGISTERS (prompt)->fp)
 167     abort ();
 168
 169   /* Capture from the top of the thunk application frame up to the end. Set an
 170      MVRA only, as the post-abort code is in an MV context. */
 171   vm_cont = scm_i_vm_capture_stack (SCM_PROMPT_REGISTERS (prompt)->sp + 4,
 172                                     SCM_VM_DATA (vm)->fp,
 173                                     SCM_VM_DATA (vm)->sp,
 174                                     NULL,
 175                                     SCM_VM_DATA (vm)->ip,
 176                                     flags);
 177
 178   ret = scm_make_program (cont_objcode,
 179                           scm_vector (scm_list_2 (vm_cont, intwinds)),
 180                           SCM_BOOL_F);
 181   SCM_SET_CELL_WORD_0 (ret,
 182                        SCM_CELL_WORD_0 (ret) | SCM_F_PROGRAM_IS_PARTIAL_CONTINUATION);
 183   return ret;
 184 }
 185
 186 void
 187 scm_c_abort (SCM vm, SCM tag, size_t n, SCM *argv, scm_t_int64 cookie)
 188 {
 189   SCM cont, winds, prompt = SCM_BOOL_F;
 190   long delta;
 191   size_t i;
 192
 193   /* Search the wind list for an appropriate prompt.
 194      "Waiter, please bring us the wind list." */
 195   for (winds = scm_i_dynwinds (), delta = 0;
 196        scm_is_pair (winds);
 197        winds = SCM_CDR (winds), delta++)
 198     {
 199       SCM elt = SCM_CAR (winds);
 200       if (SCM_PROMPT_P (elt) && scm_is_eq (SCM_PROMPT_TAG (elt), tag))
 201         {
 202           prompt = elt;
 203           break;
 204         }
 205     }
 206
 207   /* If we didn't find anything, raise an error. */
 208   if (scm_is_false (prompt))
 209     scm_misc_error ("abort", "Abort to unknown prompt", scm_list_1 (tag));
 210
 211   cont = reify_partial_continuation (vm, prompt, winds, cookie);
 212
 213   /* Unwind once more, beyond the prompt. */
 214   winds = SCM_CDR (winds), delta++;
 215
 216   /* Unwind */
 217   scm_dowinds (winds, delta);
 218
 219   /* Unwinding may have changed the current thread's VM, so use the
 220      new one.  */
 221   vm = scm_the_vm ();
 222
 223   /* Restore VM regs */
 224   SCM_VM_DATA (vm)->fp = SCM_PROMPT_REGISTERS (prompt)->fp;
 225   SCM_VM_DATA (vm)->sp = SCM_PROMPT_REGISTERS (prompt)->sp;
 226   SCM_VM_DATA (vm)->ip = SCM_PROMPT_REGISTERS (prompt)->ip;
 227
 228   /* Since we're jumping down, we should always have enough space */
 229   if (SCM_VM_DATA (vm)->sp + n + 1 >= SCM_VM_DATA (vm)->stack_limit)
 230     abort ();
 231
 232   /* Push vals */
 233   *(++(SCM_VM_DATA (vm)->sp)) = cont;
 234   for (i = 0; i < n; i++)
 235     *(++(SCM_VM_DATA (vm)->sp)) = argv[i];
 236   *(++(SCM_VM_DATA (vm)->sp)) = scm_from_size_t (n+1); /* +1 for continuation */
 237
 238   /* Jump! */
 239   SCM_I_LONGJMP (SCM_PROMPT_REGISTERS (prompt)->regs, 1);
 240
 241   /* Shouldn't get here */
 242   abort ();
 243 }
 244
 245 SCM_DEFINE (scm_at_abort, "@abort", 2, 0, 0, (SCM tag, SCM args),
 246             "Abort to the nearest prompt with tag @var{tag}.")
 247 #define FUNC_NAME s_scm_at_abort
 248 {
 249   SCM *argv;
 250   size_t i;
 251   long n;
 252
 253   SCM_VALIDATE_LIST_COPYLEN (SCM_ARG2, args, n);
 254   argv = alloca (sizeof (SCM)*n);
 255   for (i = 0; i < n; i++, args = scm_cdr (args))
 256     argv[i] = scm_car (args);
 257
 258   scm_c_abort (scm_the_vm (), tag, n, argv, -1);
 259
 260   /* Oh, what, you're still here? The abort must have been reinstated. Actually,
 261      that's quite impossible, given that we're already in C-land here, so...
 262      abort! */
 263
 264   abort ();
 265 }
 266 #undef FUNC_NAME
 267
 268 void
 269 scm_i_prompt_print (SCM exp, SCM port, scm_print_state *pstate SCM_UNUSED)
 270 {
 271   scm_puts ("#<prompt ", port);
 272   scm_intprint (SCM_UNPACK (exp), 16, port);
 273   scm_putc ('>', port);
 274 }
 275
 276 void
 277 scm_init_control (void)
 278 {
 279 #include "libguile/control.x"
 280 }
 281
 282 /*
 283   Local Variables:
 284   c-file-style: "gnu"
 285   End:
 286 */