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 k, SCM *fp, SCM *sp, scm_t_uint8 *abort_ip,
  36                    scm_t_uint8 escape_only_p, 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 = fp;
  49   regs->sp = sp;
  50   regs->ip = abort_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 /* Only to be called if the SCM_PROMPT_SETJMP returns 1 */
  61 SCM
  62 scm_i_prompt_pop_abort_args_x (SCM prompt)
  63 {
  64   size_t i, n;
  65   SCM vals = SCM_EOL;
  66
  67   n = scm_to_size_t (SCM_PROMPT_REGISTERS (prompt)->sp[0]);
  68   for (i = 0; i < n; i++)
  69     vals = scm_cons (SCM_PROMPT_REGISTERS (prompt)->sp[-(i + 1)], vals);
  70
  71   /* The abort did reset the VM's registers, but then these values
  72      were pushed on; so we need to pop them ourselves. */
  73   SCM_VM_DATA (scm_the_vm ())->sp -= n + 1;
  74   /* FIXME NULLSTACK */
  75
  76   return vals;
  77 }
  78
  79
  80 #ifdef WORDS_BIGENDIAN
  81 #define OBJCODE_HEADER(main,meta) 0, 0, 0, main, 0, 0, 0, meta+8
  82 #define META_HEADER(meta)         0, 0, 0, meta, 0, 0, 0, 0
  83 #else
  84 #define OBJCODE_HEADER(main,meta) main, 0, 0, 0, meta+8, 0, 0, 0
  85 #define META_HEADER(meta)         meta, 0, 0, 0, 0,      0, 0, 0
  86 #endif
  87
  88 #define ROUND_UP(len,align) (((len-1)|(align-1))+1)
  89 #define ALIGN_PTR(type,p,align) (type*)(ROUND_UP (((scm_t_bits)p), align))
  90
  91 #ifdef SCM_ALIGNED
  92 #define SCM_DECLARE_STATIC_ALIGNED_ARRAY(type, sym)\
  93 static const type sym[]
  94 #define SCM_STATIC_ALIGNED_ARRAY(alignment, type, sym)\
  95 static SCM_ALIGNED (alignment) const type sym[]
  96 #else
  97 #define SCM_DECLARE_STATIC_ALIGNED_ARRAY(type, sym)\
  98 static type *sym
  99 #define SCM_STATIC_ALIGNED_ARRAY(alignment, type, sym)                  \
 100 SCM_SNARF_INIT(sym = scm_malloc (sizeof(sym##__unaligned) + alignment - 1); \
 101                sym = ALIGN_PTR (type, sym, alignment);                  \
 102                memcpy (sym, sym##__unaligned, sizeof(sym##__unaligned));) \
 103 static type *sym = NULL;                                                \
 104 static const type sym##__unaligned[]
 105 #endif
 106
 107 #define STATIC_OBJCODE_TAG                                      \
 108   SCM_PACK (scm_tc7_objcode | (SCM_F_OBJCODE_IS_STATIC << 8))
 109
 110 #define SCM_STATIC_OBJCODE(sym)                                         \
 111   SCM_DECLARE_STATIC_ALIGNED_ARRAY (scm_t_uint8, sym##__bytecode);      \
 112   SCM_STATIC_ALIGNED_ARRAY (8, scm_t_cell, sym##__cells) = {            \
 113     { STATIC_OBJCODE_TAG, SCM_PACK (sym##__bytecode) },                 \
 114     { SCM_BOOL_F, SCM_PACK (0) }                                        \
 115   };                                                                    \
 116   static const SCM sym = SCM_PACK (sym##__cells);                       \
 117   SCM_STATIC_ALIGNED_ARRAY (8, scm_t_uint8, sym##__bytecode)
 118
 119
 120 SCM_STATIC_OBJCODE (cont_objcode) = {
 121   /* Like in continuations.c, but with partial-cont-call. */
 122   OBJCODE_HEADER (8, 19),
 123   /* leave args on the stack */
 124   /* 0 */ scm_op_object_ref, 0, /* push scm_vm_cont object */
 125   /* 2 */ scm_op_object_ref, 1, /* push internal winds */
 126   /* 4 */ scm_op_partial_cont_call, /* and go! */
 127   /* 5 */ scm_op_nop, scm_op_nop, scm_op_nop, /* pad to 8 bytes */
 128   /* 8 */
 129
 130   /* We could put some meta-info to say that this proc is a continuation. Not sure
 131      how to do that, though. */
 132   META_HEADER (19),
 133   /* 0 */ scm_op_make_eol, /* bindings */
 134   /* 1 */ scm_op_make_eol, /* sources */
 135   /* 2 */ scm_op_make_int8, 0, scm_op_make_int8, 5, /* arity: from ip 0 to ip 7 */
 136   /* 6 */ scm_op_make_int8_0, /* the arity is 0 required args */
 137   /* 7 */ scm_op_make_int8_0, /* 0 optionals */
 138   /* 8 */ scm_op_make_true, /* and a rest arg */
 139   /* 9 */ scm_op_list, 0, 5, /* make a list of those 5 vals */
 140   /* 12 */ scm_op_list, 0, 1, /* and the arities will be a list of that one list */
 141   /* 15 */ scm_op_list, 0, 3, /* pack bindings, sources, and arities into list */
 142   /* 18 */ scm_op_return /* and return */
 143   /* 19 */
 144 };
 145
 146
 147 static SCM
 148 reify_partial_continuation (SCM vm, SCM prompt, SCM extwinds,
 149                             scm_t_int64 cookie)
 150 {
 151   SCM vm_cont, dynwinds, intwinds = SCM_EOL, ret;
 152   scm_t_uint32 flags;
 153
 154   /* No need to reify if the continuation is never referenced in the handler. */
 155   if (SCM_PROMPT_ESCAPE_P (prompt))
 156     return SCM_BOOL_F;
 157
 158   dynwinds = scm_i_dynwinds ();
 159   while (!scm_is_eq (dynwinds, extwinds))
 160     {
 161       intwinds = scm_cons (scm_car (dynwinds), intwinds);
 162       dynwinds = scm_cdr (dynwinds);
 163     }
 164
 165   flags = SCM_F_VM_CONT_PARTIAL;
 166   if (cookie >= 0 && SCM_PROMPT_REGISTERS (prompt)->cookie == cookie)
 167     flags |= SCM_F_VM_CONT_REWINDABLE;
 168
 169   /* Since non-escape continuations should begin with a thunk application, the
 170      first bit of the stack should be a frame, with the saved fp equal to the fp
 171      that was current when the prompt was made. */
 172   if ((SCM*)(SCM_PROMPT_REGISTERS (prompt)->sp[1])
 173       != SCM_PROMPT_REGISTERS (prompt)->fp)
 174     abort ();
 175
 176   /* Capture from the top of the thunk application frame up to the end. Set an
 177      MVRA only, as the post-abort code is in an MV context. */
 178   vm_cont = scm_i_vm_capture_stack (SCM_PROMPT_REGISTERS (prompt)->sp + 4,
 179                                     SCM_VM_DATA (vm)->fp,
 180                                     SCM_VM_DATA (vm)->sp,
 181                                     NULL,
 182                                     SCM_VM_DATA (vm)->ip,
 183                                     flags);
 184
 185   ret = scm_make_program (cont_objcode,
 186                           scm_vector (scm_list_2 (vm_cont, intwinds)),
 187                           SCM_BOOL_F);
 188   SCM_SET_CELL_WORD_0 (ret,
 189                        SCM_CELL_WORD_0 (ret) | SCM_F_PROGRAM_IS_CONTINUATION);
 190   return ret;
 191 }
 192
 193 void
 194 scm_c_abort (SCM vm, SCM tag, size_t n, SCM *argv, scm_t_int64 cookie)
 195 {
 196   SCM cont, winds, prompt = SCM_BOOL_F;
 197   long delta;
 198   size_t i;
 199
 200   /* Search the wind list for an appropriate prompt.
 201      "Waiter, please bring us the wind list." */
 202   for (winds = scm_i_dynwinds (), delta = 0;
 203        scm_is_pair (winds);
 204        winds = SCM_CDR (winds), delta++)
 205     {
 206       SCM elt = SCM_CAR (winds);
 207       if (SCM_PROMPT_P (elt) && scm_is_eq (SCM_PROMPT_TAG (elt), tag))
 208         {
 209           prompt = elt;
 210           break;
 211         }
 212     }
 213
 214   /* If we didn't find anything, print a message and abort the process
 215      right here.  If you don't want this, establish a catch-all around
 216      any code that might throw up. */
 217   if (scm_is_false (prompt))
 218     {
 219       if (scm_is_eq (tag, scm_fluid_ref (scm_sys_default_prompt_tag)))
 220         {
 221           fprintf (stderr, "No prompt found for abort to default prompt tag!\n");
 222           abort ();
 223         }
 224       else
 225         scm_misc_error ("abort", "abort to unknown tag", scm_list_1 (tag));
 226     }
 227
 228   cont = reify_partial_continuation (vm, prompt, winds, cookie);
 229
 230   /* Unwind once more, beyond the prompt. */
 231   winds = SCM_CDR (winds), delta++;
 232
 233   /* Unwind */
 234   scm_dowinds (winds, delta);
 235
 236   /* Restore VM regs */
 237   SCM_VM_DATA (vm)->fp = SCM_PROMPT_REGISTERS (prompt)->fp;
 238   SCM_VM_DATA (vm)->sp = SCM_PROMPT_REGISTERS (prompt)->sp;
 239   SCM_VM_DATA (vm)->ip = SCM_PROMPT_REGISTERS (prompt)->ip;
 240
 241   /* Since we're jumping down, we should always have enough space */
 242   if (SCM_VM_DATA (vm)->sp + n + 1 >= SCM_VM_DATA (vm)->stack_limit)
 243     abort ();
 244
 245   /* Push vals */
 246   *(++(SCM_VM_DATA (vm)->sp)) = cont;
 247   for (i = 0; i < n; i++)
 248     *(++(SCM_VM_DATA (vm)->sp)) = argv[i];
 249   *(++(SCM_VM_DATA (vm)->sp)) = scm_from_size_t (n+1); /* +1 for continuation */
 250
 251   /* Jump! */
 252   SCM_I_LONGJMP (SCM_PROMPT_REGISTERS (prompt)->regs, 1);
 253
 254   /* Shouldn't get here */
 255   abort ();
 256 }
 257
 258 SCM_DEFINE (scm_at_abort, "@abort", 2, 0, 0, (SCM tag, SCM args),
 259             "Abort to the nearest prompt with tag @var{tag}.")
 260 #define FUNC_NAME s_scm_at_abort
 261 {
 262   SCM *argv;
 263   size_t i, n;
 264
 265   SCM_VALIDATE_LIST_COPYLEN (SCM_ARG2, args, n);
 266   argv = alloca (sizeof (SCM)*n);
 267   for (i = 0; i < n; i++, args = scm_cdr (args))
 268     argv[i] = scm_car (args);
 269
 270   scm_c_abort (scm_the_vm (), tag, n, argv, -1);
 271
 272   /* Oh, what, you're still here? The abort must have been reinstated. Actually,
 273      that's quite impossible, given that we're already in C-land here, so...
 274      abort! */
 275
 276   abort ();
 277 }
 278 #undef FUNC_NAME
 279
 280 void
 281 scm_init_control (void)
 282 {
 283 #include "control.x"
 284   scm_sys_default_prompt_tag = scm_make_fluid ();
 285   scm_fluid_set_x (scm_sys_default_prompt_tag, scm_gensym (SCM_UNDEFINED));
 286   scm_c_define ("%default-prompt-tag", scm_sys_default_prompt_tag);
 287 }
 288
 289 /*
 290   Local Variables:
 291   c-file-style: "gnu"
 292   End:
 293 */