libguile/control.c

   1 /* Copyright (C) 2010, 2011  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 ALIGN_PTR(type,p,align) (type*)(ROUND_UP (((scm_t_bits)p), align))
  85
  86 #ifdef 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 #else
  92 #define SCM_DECLARE_STATIC_ALIGNED_ARRAY(type, sym)     \
  93 static type *sym
  94 #define SCM_STATIC_ALIGNED_ARRAY(alignment, type, sym)                  \
  95 SCM_SNARF_INIT(sym = scm_malloc_pointerless (sizeof(sym##__unaligned); \
  96                memcpy (sym, sym##__unaligned, sizeof(sym##__unaligned));) \
  97 static type *sym = NULL;                                                \
  98 static const type sym##__unaligned[]
  99 #endif
 100
 101 #define STATIC_OBJCODE_TAG                                      \
 102   SCM_PACK (SCM_MAKE_OBJCODE_TAG (SCM_OBJCODE_TYPE_STATIC, 0))
 103
 104 #define SCM_STATIC_OBJCODE(sym)                                         \
 105   SCM_DECLARE_STATIC_ALIGNED_ARRAY (scm_t_uint8, sym##__bytecode);      \
 106   SCM_STATIC_ALIGNED_ARRAY (8, scm_t_cell, sym##__cells) = {            \
 107     { STATIC_OBJCODE_TAG, SCM_PACK (sym##__bytecode) },                 \
 108     { SCM_BOOL_F, SCM_PACK (0) }                                        \
 109   };                                                                    \
 110   static const SCM sym = SCM_PACK (sym##__cells);                       \
 111   SCM_STATIC_ALIGNED_ARRAY (8, scm_t_uint8, sym##__bytecode)
 112
 113
 114 SCM_STATIC_OBJCODE (cont_objcode) = {
 115   /* Like in continuations.c, but with partial-cont-call. */
 116   OBJCODE_HEADER (8, 19),
 117   /* leave args on the stack */
 118   /* 0 */ scm_op_object_ref, 0, /* push scm_vm_cont object */
 119   /* 2 */ scm_op_object_ref, 1, /* push internal winds */
 120   /* 4 */ scm_op_partial_cont_call, /* and go! */
 121   /* 5 */ scm_op_nop, scm_op_nop, scm_op_nop, /* pad to 8 bytes */
 122   /* 8 */
 123
 124   /* We could put some meta-info to say that this proc is a continuation. Not sure
 125      how to do that, though. */
 126   META_HEADER (19),
 127   /* 0 */ scm_op_make_eol, /* bindings */
 128   /* 1 */ scm_op_make_eol, /* sources */
 129   /* 2 */ scm_op_make_int8, 0, scm_op_make_int8, 5, /* arity: from ip 0 to ip 7 */
 130   /* 6 */ scm_op_make_int8_0, /* the arity is 0 required args */
 131   /* 7 */ scm_op_make_int8_0, /* 0 optionals */
 132   /* 8 */ scm_op_make_true, /* and a rest arg */
 133   /* 9 */ scm_op_list, 0, 5, /* make a list of those 5 vals */
 134   /* 12 */ scm_op_list, 0, 1, /* and the arities will be a list of that one list */
 135   /* 15 */ scm_op_list, 0, 3, /* pack bindings, sources, and arities into list */
 136   /* 18 */ scm_op_return /* and return */
 137   /* 19 */
 138 };
 139
 140
 141 static SCM
 142 reify_partial_continuation (SCM vm, SCM prompt, SCM extwinds,
 143                             scm_t_int64 cookie)
 144 {
 145   SCM vm_cont, dynwinds, intwinds = SCM_EOL, ret;
 146   scm_t_uint32 flags;
 147
 148   /* No need to reify if the continuation is never referenced in the handler. */
 149   if (SCM_PROMPT_ESCAPE_P (prompt))
 150     return SCM_BOOL_F;
 151
 152   dynwinds = scm_i_dynwinds ();
 153   while (!scm_is_eq (dynwinds, extwinds))
 154     {
 155       intwinds = scm_cons (scm_car (dynwinds), intwinds);
 156       dynwinds = scm_cdr (dynwinds);
 157     }
 158
 159   flags = SCM_F_VM_CONT_PARTIAL;
 160   if (cookie >= 0 && SCM_PROMPT_REGISTERS (prompt)->cookie == cookie)
 161     flags |= SCM_F_VM_CONT_REWINDABLE;
 162
 163   /* Since non-escape continuations should begin with a thunk application, the
 164      first bit of the stack should be a frame, with the saved fp equal to the fp
 165      that was current when the prompt was made. */
 166   if ((SCM*)SCM_UNPACK (SCM_PROMPT_REGISTERS (prompt)->sp[1])
 167       != SCM_PROMPT_REGISTERS (prompt)->fp)
 168     abort ();
 169
 170   /* Capture from the top of the thunk application frame up to the end. Set an
 171      MVRA only, as the post-abort code is in an MV context. */
 172   vm_cont = scm_i_vm_capture_stack (SCM_PROMPT_REGISTERS (prompt)->sp + 4,
 173                                     SCM_VM_DATA (vm)->fp,
 174                                     SCM_VM_DATA (vm)->sp,
 175                                     NULL,
 176                                     SCM_VM_DATA (vm)->ip,
 177                                     flags);
 178
 179   ret = scm_make_program (cont_objcode,
 180                           scm_vector (scm_list_2 (vm_cont, intwinds)),
 181                           SCM_BOOL_F);
 182   SCM_SET_CELL_WORD_0 (ret,
 183                        SCM_CELL_WORD_0 (ret) | SCM_F_PROGRAM_IS_PARTIAL_CONTINUATION);
 184   return ret;
 185 }
 186
 187 void
 188 scm_c_abort (SCM vm, SCM tag, size_t n, SCM *argv, scm_t_int64 cookie)
 189 {
 190   SCM cont, winds, prompt = SCM_BOOL_F;
 191   long delta;
 192   size_t i;
 193
 194   /* Search the wind list for an appropriate prompt.
 195      "Waiter, please bring us the wind list." */
 196   for (winds = scm_i_dynwinds (), delta = 0;
 197        scm_is_pair (winds);
 198        winds = SCM_CDR (winds), delta++)
 199     {
 200       SCM elt = SCM_CAR (winds);
 201       if (SCM_PROMPT_P (elt) && scm_is_eq (SCM_PROMPT_TAG (elt), tag))
 202         {
 203           prompt = elt;
 204           break;
 205         }
 206     }
 207
 208   /* If we didn't find anything, raise an error. */
 209   if (scm_is_false (prompt))
 210     scm_misc_error ("abort", "Abort to unknown prompt", scm_list_1 (tag));
 211
 212   cont = reify_partial_continuation (vm, prompt, winds, cookie);
 213
 214   /* Unwind once more, beyond the prompt. */
 215   winds = SCM_CDR (winds), delta++;
 216
 217   /* Unwind */
 218   scm_dowinds (winds, delta);
 219
 220   /* Unwinding may have changed the current thread's VM, so use the
 221      new one.  */
 222   vm = scm_the_vm ();
 223
 224   /* Restore VM regs */
 225   SCM_VM_DATA (vm)->fp = SCM_PROMPT_REGISTERS (prompt)->fp;
 226   SCM_VM_DATA (vm)->sp = SCM_PROMPT_REGISTERS (prompt)->sp;
 227   SCM_VM_DATA (vm)->ip = SCM_PROMPT_REGISTERS (prompt)->ip;
 228
 229   /* Since we're jumping down, we should always have enough space */
 230   if (SCM_VM_DATA (vm)->sp + n + 1 >= SCM_VM_DATA (vm)->stack_limit)
 231     abort ();
 232
 233   /* Push vals */
 234   *(++(SCM_VM_DATA (vm)->sp)) = cont;
 235   for (i = 0; i < n; i++)
 236     *(++(SCM_VM_DATA (vm)->sp)) = argv[i];
 237   *(++(SCM_VM_DATA (vm)->sp)) = scm_from_size_t (n+1); /* +1 for continuation */
 238
 239   /* Jump! */
 240   SCM_I_LONGJMP (SCM_PROMPT_REGISTERS (prompt)->regs, 1);
 241
 242   /* Shouldn't get here */
 243   abort ();
 244 }
 245
 246 SCM_DEFINE (scm_at_abort, "@abort", 2, 0, 0, (SCM tag, SCM args),
 247             "Abort to the nearest prompt with tag @var{tag}.")
 248 #define FUNC_NAME s_scm_at_abort
 249 {
 250   SCM *argv;
 251   size_t i;
 252   long n;
 253
 254   SCM_VALIDATE_LIST_COPYLEN (SCM_ARG2, args, n);
 255   argv = alloca (sizeof (SCM)*n);
 256   for (i = 0; i < n; i++, args = scm_cdr (args))
 257     argv[i] = scm_car (args);
 258
 259   scm_c_abort (scm_the_vm (), tag, n, argv, -1);
 260
 261   /* Oh, what, you're still here? The abort must have been reinstated. Actually,
 262      that's quite impossible, given that we're already in C-land here, so...
 263      abort! */
 264
 265   abort ();
 266 }
 267 #undef FUNC_NAME
 268
 269 void
 270 scm_i_prompt_print (SCM exp, SCM port, scm_print_state *pstate SCM_UNUSED)
 271 {
 272   scm_puts_unlocked ("#<prompt ", port);
 273   scm_intprint (SCM_UNPACK (exp), 16, port);
 274   scm_putc_unlocked ('>', port);
 275 }
 276
 277 void
 278 scm_init_control (void)
 279 {
 280 #include "libguile/control.x"
 281 }
 282
 283 /*
 284   Local Variables:
 285   c-file-style: "gnu"
 286   End:
 287 */