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 #define PROMPT_ESCAPE_P(p)                              \
  34   (SCM_DYNSTACK_TAG_FLAGS (SCM_DYNSTACK_TAG (p))        \
  35    & SCM_F_DYNSTACK_PROMPT_ESCAPE_ONLY)
  36
  37 \f
  38
  39
  40 scm_t_prompt_registers*
  41 scm_c_make_prompt_registers (SCM *fp, SCM *sp, scm_t_uint8 *abort_ip,
  42                              scm_t_int64 vm_cookie)
  43 {
  44   scm_t_prompt_registers *regs;
  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 regs;
  53 }
  54
  55 /* Only to be called if the SCM_I_SETJMP returns 1 */
  56 SCM
  57 scm_i_prompt_pop_abort_args_x (SCM vm)
  58 {
  59   size_t i, n;
  60   SCM vals = SCM_EOL;
  61
  62   n = scm_to_size_t (SCM_VM_DATA (vm)->sp[0]);
  63   for (i = 0; i < n; i++)
  64     vals = scm_cons (SCM_VM_DATA (vm)->sp[-(i + 1)], vals);
  65
  66   /* The abort did reset the VM's registers, but then these values
  67      were pushed on; so we need to pop them ourselves. */
  68   SCM_VM_DATA (vm)->sp -= n + 1;
  69   /* FIXME NULLSTACK */
  70
  71   return vals;
  72 }
  73
  74
  75 #ifdef WORDS_BIGENDIAN
  76 #define OBJCODE_HEADER(main,meta) 0, 0, 0, main, 0, 0, 0, meta+8
  77 #define META_HEADER(meta)         0, 0, 0, meta, 0, 0, 0, 0
  78 #else
  79 #define OBJCODE_HEADER(main,meta) main, 0, 0, 0, meta+8, 0, 0, 0
  80 #define META_HEADER(meta)         meta, 0, 0, 0, 0,      0, 0, 0
  81 #endif
  82
  83 #define OBJCODE_TAG SCM_MAKE_OBJCODE_TAG (SCM_OBJCODE_TYPE_STATIC, 0)
  84
  85 #if defined (SCM_ALIGNED)
  86 #define SCM_DECLARE_STATIC_ALIGNED_ARRAY(type, sym)     \
  87 static const type sym[]
  88 #define SCM_STATIC_ALIGNED_ARRAY(alignment, type, sym)  \
  89 static SCM_ALIGNED (alignment) const type sym[]
  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     { SCM_PACK (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 #else
  99 #define SCM_STATIC_OBJCODE(sym)                                         \
 100 static SCM sym;                                                         \
 101 static scm_t_uint8 *sym##_bytecode;                                     \
 102 SCM_SNARF_INIT(sym##_bytecode = scm_gc_malloc_pointerless (sizeof(sym##_bytecode__unaligned), "partial continuation stub"); \
 103                memcpy (sym##_bytecode, sym##_bytecode__unaligned, sizeof(sym##_bytecode__unaligned));) \
 104 SCM_SNARF_INIT(sym = scm_double_cell (OBJCODE_TAG,                      \
 105                                       (scm_t_bits)sym##_bytecode,       \
 106                                       SCM_UNPACK (SCM_BOOL_F),          \
 107                                       0);)                              \
 108 static const scm_t_uint8 sym##_bytecode__unaligned[]
 109 #endif
 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_partial_cont_call, /* and go! */
 118   /* 3 */ scm_op_nop,
 119   /* 4 */ scm_op_nop, 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, 3, /* arity: from ip 0 to ip 3 */
 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_t_prompt_registers *regs,
 141                             scm_t_dynstack *dynstack,
 142                             scm_t_int64 cookie)
 143 {
 144   SCM vm_cont, ret;
 145   scm_t_uint32 flags;
 146
 147   flags = SCM_F_VM_CONT_PARTIAL;
 148   if (cookie >= 0 && regs->cookie == cookie)
 149     flags |= SCM_F_VM_CONT_REWINDABLE;
 150
 151   /* Since non-escape continuations should begin with a thunk application, the
 152      first bit of the stack should be a frame, with the saved fp equal to the fp
 153      that was current when the prompt was made. */
 154   if ((SCM*)SCM_UNPACK (regs->sp[1]) != regs->fp)
 155     abort ();
 156
 157   /* Capture from the top of the thunk application frame up to the end. Set an
 158      MVRA only, as the post-abort code is in an MV context. */
 159   vm_cont = scm_i_vm_capture_stack (regs->sp + 4,
 160                                     SCM_VM_DATA (vm)->fp,
 161                                     SCM_VM_DATA (vm)->sp,
 162                                     NULL,
 163                                     SCM_VM_DATA (vm)->ip,
 164                                     dynstack,
 165                                     flags);
 166
 167   ret = scm_make_program (cont_objcode,
 168                           scm_c_make_vector (1, vm_cont),
 169                           SCM_BOOL_F);
 170   SCM_SET_CELL_WORD_0 (ret,
 171                        SCM_CELL_WORD_0 (ret) | SCM_F_PROGRAM_IS_PARTIAL_CONTINUATION);
 172   return ret;
 173 }
 174
 175 void
 176 scm_c_abort (SCM vm, SCM tag, size_t n, SCM *argv, scm_t_int64 cookie)
 177 {
 178   SCM cont;
 179   scm_t_dynstack *dynstack = &SCM_I_CURRENT_THREAD->dynstack;
 180   scm_t_bits *prompt;
 181   scm_t_prompt_registers *regs;
 182   scm_t_dynstack_prompt_flags flags;
 183   size_t i;
 184
 185   prompt = scm_dynstack_find_prompt (dynstack, tag, &regs, &flags);
 186
 187   if (!prompt)
 188     scm_misc_error ("abort", "Abort to unknown prompt", scm_list_1 (tag));
 189
 190   /* Only reify if the continuation referenced in the handler. */
 191   if (flags & SCM_F_DYNSTACK_PROMPT_ESCAPE_ONLY)
 192     cont = SCM_BOOL_F;
 193   else
 194     {
 195       scm_t_dynstack *captured;
 196
 197       captured = scm_dynstack_capture (dynstack, SCM_DYNSTACK_NEXT (prompt));
 198       cont = reify_partial_continuation (vm, regs, captured, cookie);
 199     }
 200
 201   /* Unwind.  */
 202   scm_dynstack_unwind (dynstack, prompt);
 203
 204   /* Unwinding may have changed the current thread's VM, so use the
 205      new one.  */
 206   vm = scm_the_vm ();
 207
 208   /* Restore VM regs */
 209   SCM_VM_DATA (vm)->fp = regs->fp;
 210   SCM_VM_DATA (vm)->sp = regs->sp;
 211   SCM_VM_DATA (vm)->ip = regs->ip;
 212
 213   /* Since we're jumping down, we should always have enough space.  */
 214   if (SCM_VM_DATA (vm)->sp + n + 1 >= SCM_VM_DATA (vm)->stack_limit)
 215     abort ();
 216
 217   /* Push vals */
 218   *(++(SCM_VM_DATA (vm)->sp)) = cont;
 219   for (i = 0; i < n; i++)
 220     *(++(SCM_VM_DATA (vm)->sp)) = argv[i];
 221   *(++(SCM_VM_DATA (vm)->sp)) = scm_from_size_t (n+1); /* +1 for continuation */
 222
 223   /* Jump! */
 224   SCM_I_LONGJMP (regs->regs, 1);
 225
 226   /* Shouldn't get here */
 227   abort ();
 228 }
 229
 230 SCM_DEFINE (scm_at_abort, "@abort", 2, 0, 0, (SCM tag, SCM args),
 231             "Abort to the nearest prompt with tag @var{tag}.")
 232 #define FUNC_NAME s_scm_at_abort
 233 {
 234   SCM *argv;
 235   size_t i;
 236   long n;
 237
 238   SCM_VALIDATE_LIST_COPYLEN (SCM_ARG2, args, n);
 239   argv = alloca (sizeof (SCM)*n);
 240   for (i = 0; i < n; i++, args = scm_cdr (args))
 241     argv[i] = scm_car (args);
 242
 243   scm_c_abort (scm_the_vm (), tag, n, argv, -1);
 244
 245   /* Oh, what, you're still here? The abort must have been reinstated. Actually,
 246      that's quite impossible, given that we're already in C-land here, so...
 247      abort! */
 248
 249   abort ();
 250 }
 251 #undef FUNC_NAME
 252
 253 void
 254 scm_init_control (void)
 255 {
 256 #include "libguile/control.x"
 257 }
 258
 259 /*
 260   Local Variables:
 261   c-file-style: "gnu"
 262   End:
 263 */